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www.americanradiohistory.com
MUSIC
MATES!
RCA -7199 and RCA-7027... Perfect Pair For High -Fidelity Amplifier Designs
Offer them a "top" note. Send your "deepest" bass. Blast your "fullest" fortissimo at them. Never fear the outcome if your high -fidelity amplifier is designed
around this "perfect pair "...RCA -7199, medium-mu triode sharp -cutoff pentode
and RCA -7027, beam power tube.
Study the sensitivity of the high g,,, pentode unit of the RCA -7199... wonderful for use in a low -noise low -hum amplifier; consider the medium -mu triode
unit...ideally suited for use in a phase splitter. On the masculine side of the table
is the other "mate ", RCA -7027, developed specifically to reproduce the "big
sounds ". A pair of 7027's in a push -pull class AB, circuit utilizing feedback and
driven by a 7199 with an input signal of 1 volt can deliver a power output of
50 watts with total harmonic distortion of less than 0.5% and hum and noise of
85 db below 50 watts.
Ask your RCA Field Representative for the details on the High-Fidelity
"Music Mates'.'.. RCA -7199 and RCA-7027. For technical bulletins, write RCA
Commercial Engineering, Section C- 91 -DE, Harrison, N. J.
RADIO CORPORATION OF AMERICA
Electron Tube Division
Harrison, N. J.
www.americanradiohistory.com
RCA -7199 and RCA -7027... music mates and
quality mates...blend into a system that provides music reproduction at its finestl
EAST:744 Broad Street, Newark 2, N.J.
HUmboldt 5 -3900
MIDWEST:Suite 1154,Merchandise Mart Plaza
Chicago 54, III. WHiteholl 4-2900
WEST:6355 E. Washington Boulevard
Los Angeles 22, Calif. RAymond 3 -8361
MARCH, 1959
VOL. 43, No. 3
I
for Ultimate Fidelity
Successor to RADIO, Est. 1917.
STEREO
AU D i 0
ENGINEERING
MUSIC
°"
SHERWOOD'
SOUND REPRODUCTION
C. G.
'outstanding honors
McProud, Editor and Publisher
bestowed, unsolicited,
by most recognized
Henry A. Schober, Business Manager
Harrie K. Richardson, Associate Editor
Linda Sueskind, Assistant Editor
testing organizations.
a,tttttt
Janet M. Durgin, Production Manager
Edgar E. Newman, Circulation Director
Sanford
L.
Cahn, Advertising Director
-
Midwest Representative
W. A. Cook and Associates
161 East Grand Are., Chicago 11, III.
Brest Coast Representative
James C. Calloway
65.35 Wilshire Boulevard, Los Angeles 48, Calif.
teer
-
LI.'
CONTENTS
Audioclinic-Joseph Gioranelli
2
Live i... Recorded Concert
4
6
Letters
Audio ETC -Edward Talpal! C'nnbry
Editor's Review
Loading the Piezoelectric ('artridge- Iferunt Burstein
Design of the Wide -Range Ultra- Compact Regal Speaker System-1?oberl C
Aredon, Wayne Kona, and Jack E. Burchfield
The Decibel-Fact or Fable?- ll'al'er R. Westphal
Acoustic -Front Damping in Dynamic Microphones-W. T. Finir
New York's Audio Workshop-Sidney Nneins!'ll
60 -Watt Amplifier With a Silicon Rectifier Power Supply -L. B. Ilnhell _.
Transformer Distortion -Danford Kelly-Part Il.
Equipment Profile--Bell "Carillon" stereo aTnplifer- Knight -Kit stereo preamplifier
__... .._.....
Record Revue-Edward nation Canby
Jazz and All That -Charles A. Roberlsmt
New Products
Coming Hi Fi Shows
About Music-Han r,lr! Lawrence
New Literature
Industry Notes & People
Advertising Index _._
.
_
.
..
_
12
19
21
22
27
28
34
36
42
48
54
60
70
79
SO
81
87
88
COVER PHOTO- "Unobstrusive" Electro-Voice Regal speaker systems in "The
House of Music," home of E-V's sales veep Lawrence LeKashntan. Except for the
lavatories, which have monophonic systems, every room in the house is equipped
with stereo, some using large speakers, some small. Main equipment is housed in
a rack in the living room, with a secondary system in the dining room for independent programming when desirable.
AUDIO
(title
registered U. S. Pat. Oft ) is published monthly by Radio Magazines. Inc., Henry
A. Schober, President:
C. C. McProud, Secretary. Executive and Editorial Offices. 204 Front St., Mineola,
N. Y. Subscription rata
S.
Possessions, Canada mid Mexico, $4 00 for one
year, $7.60 for two years, all other countries, $5.00 per year. Single
copies 500. Printed in U.S.A. at Lancaster, Pa. All rights reserved. Entire contents
copyrighted 1959 by Radio Magazines.
Inc. Entered as Second Class Matter February 9, 1950 at the Pest Office, Lancaster. Pa. under the
Act of Man h 3, 1379.
-U.
RADIO MAGAZINES, INC., P. O. Box 629, MINEOLA, N. Y.
Postmaster: Send Form 3579 to AUDIO, P. O. Box 629, Mineola,
AUDIO
N. Y.
If your choice is stereo, Sherwood
offers The Ultimate-a dual 20 +20 watt
amplifier for stereo "in a single
package"; or a 20 watt
"add- stereo" amplifier.
Basic coordinated controls for either
stereo or monaural operation include 10
two -channel controls, stereo normal/
reverse switch, phase inversion switch,
and dual amplifier monaural operation
with either set of input sources. The five
modes of operation (stereo,
stereo -reversed, monaural 1, monaural 2,
monaural 1 +2) are selected by the
function switch which also operates a
corresponding group of indicator lites to
identify the selected operating mode
Model 5.4000 -20 Watt "AddStereo" Amplifier,
Fair Trade $109.50
-
Model S-5000 20+20 Watt Stereo Dual
Amplifier, Fair Trade $189.50
I' or complete specifications
write Dept.
A -3.
SHERWOOD
ELECTRONIC LABORATORIES, INC.
1300
N
California Ave
,
Chicago 18. Illinois
The "complete high fidelity home music center"
monophonic or stereophonic.
-
r,
riY-
MARCH, 1959
1
www.americanradiohistory.com
AUDIOCLINIC ??
TOP BUY IN HI -FI
Master- EngineeredMaster -Crafted!
JOSEPH
GIOVANELLI
TRANSISTOR
STEREO
Connecting Headphones to Amplifiers
PREAMPLIFIER
EQUALIZER
Clean,
hum -free
con
trot and amplification.
Straight DC operation -no microphonies or tubs noises. Sep-
arate bass and treble controls for each channel plus common
and
balancing controls. Six hi- Impedance inputs; four
equalized in- Impedance inputs; two levels on "magnetic" for
both low and high output cartridges without external transformer. Four output lacks for amplifier and tape. Channel
reverse switch. AC control switch. Power drain so low that
battery lasts almost full "shelf -life ". Size 3" x 9" x 5'/ ";
weight 4 lbs. Model 41, less battery, with cabinet.
Model 24, similar, but single channel,
$59.50,
$34.50.
represent the 500 -ohm winding, and your
phones may be connected directly to these
DELUXE
WILLIAMSON -TYPE
20 -WATT
AMPLIFIER
Uses
famous
Williamson
circuit with
fications
unique
for
tru
modl
hi
fidelity reproduction at Increased power output. Ultra -linear
operation; screentapped primary output transformer. Frequency response gat and smooth thre entire audible range,
with distortion less than .0025 at normal listening levels,
excellent transient characteristics. 20 -watt undistorted
output; 4-8-16 ohm output Impedances. The perfect balle
amplifier for stereo systems. Size, 9" x 12" x 6' "2"; weight,
and
27 lbs.
Model 15W,
$59.95,
STEREO -MATIC
10 -WATT
2- CHANNEL
AMPLIFIER
Beth channel; have independent volume and tone controls.
Power transformer supply, good regulation, line Isolation.
Binaural and monaural operation. With stereo piezo -type
cartridge, will amplify all single and dual -track records.
Tuners, microphones, etc. can be fed Into Stereo - Matie by
adding external switch or connectors. Size, 3'.ú" x 9 %" a
5 "; weight, B lbs. Model 39,
Model 39A,
similar, but with built -in selector switch,
$29.95.
$34.50.
15 -WATT
CONTROLLED
AMPLIFIER
BUILT-IN
pins.
However, there is another factor which
should be taken into account. Earphones
are placed very close to the eardrums,
thereby creating a very efficient coupling
network. This means that only a small
amount of power is necessary for good
listening level in the headphones. In fact,
the power required for adequate listening
level is approximately 9 milliwatts, or
9/1000 of one watt. This means that the
volume control need he turned but slightly
to produce such a low power level in its
output circuit. This small degree of volume
control rotation will make it difficult to
operate your amplifier smoothly.
This difficulty may he overcome through
the use of a pad. It may be constructed
as follows: Connect a 500-ohm resistor
across pins 7 and 8 of the output plug on
your amplifier, the 500 -ohm tap. Use a
5 -watt wire wound resistor. Connect a
4700 -ohm, 1 -watt resistor to pin 7. Connect a similar resistor to pin 8. Connect the
free ends of these resistors to the headphone terminals. By this means you will
have introduced a loss into the system, a
voltage division of 20 to L Naturally, considerably more power will be needed to
drive the headphones with this pad in the
circuit.
ELECTRONIC
CROSS -OVER
preamp with two output transformers,
circuits using EL -84's in push -pull for
and 60E7 single end for high frequency
control governs cross -over action. Inde.
plexo and
pendent bass and treble controls. Magnetic,
auxiliary Inputs. Equalization for RIAA. STEREO ADAPTOR SOCKET for esing two model 22 amplifiers In binaural
operation. Front panel removable for cabinet or custom Installation. Size, 4" x 14" x 6'u "; weight. 14 lbs. Model
amplifier and
hi -lo output
thru midrange
response. Brilliance
Hi -fl
Dual
bass
22,
I
would like to know how to connect
a pair of 600 -ohm headphones to my Brook
amplifier. John Sabritt, Philadelphia, Pa.
A. The Brook amplifier is it special case
in that it includes a 500 -ohm winding in
its design. Furthermore, this amplifier is
fitted with an octal plug, rather than the
conventional tie strip used to connect loudspeakers and other d sviccs to most other
amplifiers. Pins 7 and 8 on this output plug
Q.
$49.95.
DUO- MASTER
PLUG-IN
REMOTE -CONTROL
TV TUNER
a single,
thin, coaxial lead Into your TV receiver
select your stations, fine -tune both picture and
from your armand adjust picture Intensity
chair (to 50 feet from screen). Use loudspeaker of DooM aster or the speaker In your own TV or hi-fl system
any combination
or plug headphones right Into Due Master for private listening. A complete TV sound receiver, ideal for tape -recording TV programs. Three IF
stages; two audio stages. HI -gain, positive switch action
delivers strong audio
tuner. Revitalizes any receiver
and video signals. 9 tubes plus rectifier. Size, 121/2" x 8"
x 6 "; weight. 15 lbs. Model 23A,
lust plug
and you can
-right
sound.
-er
.
.
$79.50.
Ask your dealer
or write direct to;
TECH -MASTER CORPORATION
75 FRONT STREET, BROOKLYN 1, N.Y.
The pad has another advantage. Because
of the high sensitivity of the headphones,
any residual hiss level in the amplifier will
be present as an annoying background to
the program material being listened to.
The pad will attenuate this background
noise to a level such that it will be barely
noticeable.
Other amplifiers are not provided with
a 500 -ohm winding, but these also may be
connected to 600 -oihm phones. The amplifier
again should be properly loaded with a
resistor connected across the output tap
selected. If, for example, the 8 -ohm tap is
to be used, it should be of perhaps 5 watts
capacity. A similar voltage-dividing network should be used between the 8-ohm
resistor and the headphones. If you wish
to experiment in order to obtain the best
signal to noise ratio, make the resistances
variable. Once you have selected the desired settings, measure the resistors and
substitute fixed values.
The headphones may also be connected
directly to the output of your preamplifier.
600 -ohm headphones will unfortunately
load down most cathode -follower circuits,
and this loading will cause a degradation
of low- frequency response, which is already badly degraded because of the nature
of most of the headphones employed. High impedance phones, especially crystals, may
a 34,20
Newkirk Ave., Brooklyn 3, N. Y.
he connected directly to the output of the
preamplifier without such degradation.
Speaker Efficiency
Q. Would you please enlighten me as to
the relationship between power output of
an amplifier and the efficiency of a speaker?
For example, I am using a speaker whose
efficiency is 10 per cent. How powerful an
amplifier do I need in order to drive the
speaker sufficiently to obtain $0 watts of
musical program level? Can it be that we
only obtain two watts output from a 10
per cent efficient speaker when this speaker
is driven by a 20 -watt amplifier? Fernando
Sim, Manila, Philippines.
A. When a speaker has a maximum
power handling capacity of 20 watts, it
means that 20 watts is the top amount of
power which can be fed into the speaker
without damaging it or causing serious
distortion. If the speaker is 10 per cent
efficient, it will when supplied with this
maximum of 20 watts, produce 2 watts of
acoustical output. Remember that, by
definition, efficiency is equal to the power
fed into a device, divided by the power output, or yield, of that device. 2 watts output,
as in this example, sounds like a small
amount of power, but bear in mind that a
full symphony orchestra playing at top
fortissimo only develops about a watt of
acoustical power. Because of this, you will
not need a 20 -watt program level from
your speaker system. (Such a level would
most certainly injure your ears, were you
to stand near the system when it is giving
out with that much sound.) However,
assuming that for some reason you do need
such high program levels, and further assuming that your speaker system is 10
per cent efficient, you would need an amplifier capable of delivering a power output
of 200 watts in order that these conditions
be met. Further, you would need a speaker
system whose power input capabilities are
at last equal to 200 watts, and if tisis program level is to he maintained over long
periods, you would need a system capable
of peak power levels of from 250 to 300
watts.
Volume Controls and Power Amplifiers
Q. I have a power amplifier having an
input grid resistor of 1 megohnn. I also
have two preamplifiers and I would like
to connect a volume control to each of their
outputs in order to improve signal -to -noise
ratio. What value of volume control would
you recommend that I use? Neither preamplifier has a cathode follower. Would it be
better to locate the volume control at the
end of the preamplifier or locate it at the
input of the power amplifier? What are
the general principles involved in determining the resistance of a volume control?
S. W., New York City, N. Y.
A. First, remove the input grid resistor
from the power amplifier- Connect a volume
control of the same value in its place.
(Later in this answer I will outline the
means of determining the correct value of
control. Check to see whether the control
you substitute conforms to this procedure.)
Be sure that the grid of the amplifier is
connected to the arm of the control. The
leads of the input connector on the power
AUDIO
2
www.americanradiohistory.com
MARCH, 1959
DON'T COMPROMISE
WITH QUALITY...
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engineered to
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cartridges at
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weight. thus
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and record wear.
arms.
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With the
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track all
transcription
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Convenient
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It is precision -
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GARRARD SALES CORPORATION, Dir. of British Industries Core. Port Wuhin1ton, Pl. Y.
Canadian Inquiries to Chas. W. Pointens lid., 6 Alcina Ave., Toronto
Territories other than U.S.A. and Canada to Garrard Engineering 6 MIg. Co., ltd., Swindon, Wilts., England
www.americanradiohistory.com
Port Washington, New York.
Please send your new comparator guide
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Canard Sales Corporation, Dept. GC -19
i
irish
ferro -sheen
recording
tape
amplifier are connected across the full resistance of the control. The method of
determining the value of a volume control
is the same as that employed when determining the value of a grid -load resistor. It should be at least twice as large
as its preceding plate -load resistor. The
value of the interstage coupling capacitor
is also a factor. Its reactance at the lowest
audio frequency you wish to pass should
be considerably lower than the grid resistance.
It would be better if the control units
employed cathode -follower outputs. This
is especially true when the control units are
to be located some distance from the amplifier because the length of the interconnecting cable will then be great enough
to introduce considerable capacitive reactance which, in turns, will cause sonic
degradation of the high frequencies. This
condition does not prevail with cathodefollower circuits largely because their impedance is much lower than the capacitive
reactance of the shielded cable, and hence,
the shunting effect of this reactance is
negligible.
Matrixing
Q.
I
have
heard much
matrixing. Just what
is
it?
lately about
Long
G. Best,
Island City, N. P.
irish
ferro -sheen
recording
tape
irish
ferro -sheen
recording
tape:
A. Matrixing is a system whereby two
signals are combined to form their sum
and their difference; later they are reconstituted into their original components.
This technique is employed in the Crosby
multiplex system. The sum of two stereo
channels is fed into an FM transmitter in
the normal manner. (Those who don't have
multiplex adapters may, by this means,
receive the monophonic broadcast.) The
difference signal is impressed upon a sub carrier, which is transmitted on the vain
FM carrier. This subcarrier is undetectable
with unmodified FM receivers, but this
difference information can be recovered by
adding a multiplex adapter to the tuner.
Some circuit modification will he needed
on tuners which were not provided with a
multiplex jack. One of the things which
is included in the adapter is a matrixing
circuit, which serves to recover the difference signal and recombine it wilh the sum
signal in such a way that the original
stereo information is recovered and can be
fed to the stereo preamplifier in the usual
manner.
Another use found for this technique is
the Columbia Record stereo system, which
matrixes the signal and records the sum
signal laterally and the difference signal
vertically, with compression on the difference, or vertical channel.
Live vs. Recorded Concert
Occasionally put on in a large scale by
bigger organizations, live vs. recorded music concerts are always interesting to the serious audiofan. On a smaller
scale -from the point of view of number
concert staged last Januof musicians
ary 10 at Carnegie Recital Hall was no less
informative and entertaining.
The participating organizations were:
The Fine Arts Quartet, shown below, con prised of Leonard Sorkin and Abraham
Loft, violins, Irving Inner, viola, and
George Sorkin, cello; Concertapes, Inc..
with its professional recording equipment
and techniques; Dynaco, Inc., with two
Dyuakit preamplifiers and two Mark III
amplifiers; and Acoustic Research, Inc.,
with two AR-3 speaker systems. The concert was actually presented three times to
accommodate those who were invited to
attend, this in itself being a record.
much
-a
Just prior to the concerts, a tape recording was made of the quartet playing the
programmed selections. The reproducing
system was then adjusted for the same
sound volume as that from the quartet.
Synchronization between the tape and the
musicians permitted the latter to stop play ing while the tape took over. Even while
watching the musicians carefully, many of
the audience were unable to determine
which source they were listening to. The
program notes for the concert suggest that
such a comparison is the final test of "high
fidelity" recording techniques and reproducing equipment, and that if the audience
cannot detect the switchovers the demonstration would be successful. By this criterion we would have to say that it achieved
at least 90 per cent of success.
-CGMcP
It's the best- engineered tape
in the world...
...gives you better highs...better lows...
better sound all around! Saves your tape
-
recorder, too because the Irish FERROSHEEN process results in smoother tape
...tape that can't sand down your magnetic heads or shed oxide powder into your
machine. Price? Same as ordinary tape!
Available wherever quality tape is sold.
ORRadio Industries, Inc., Opelika, Alabama
Metropolitan Opera Star George London is managed
by Columbia Artists Management Inc.
AUDIO
4
www.americanradiohistory.com
o
MARCH, 1959
Perfectly matched to the Tandberg Stereo
playback amplifiers, Tandberg Model 266
Speaker Enclosure is truly an outstanding
performer in faithfully reproducing
sound over a wide frequency range with
lowest distortion. Functional in design,
it is beautifully finished with mahogany
on all sides to enable either horizontal
or vertical placement. With the
Tandberg 5, two Model 266 enclosures
make up a complete Stereo tape system.
The HULDRA 5 is an AM -FM Shortwave Tuner,
Preamplifier, Power Amplifier and Intercommunications
System with FM Multiplex Output combined in
one beautiful Scandinavian "package." More extraordinary
than styling is the technical brilliance it represents.
Probably the most sensitive tuner ever designed and
manufactured, Huldra 5 positively assures wide range,
distortion -free response made possible by its
carefully designed circuitry. No other tuner has the
versatility nor unlimited quality of Huldra 5.
ti
iireem.,-4311*A
TANDBERG
Here is the distinctive Tandberg 5
Stereophonic tape recorder, in itself
audio ingenuity without equal! It proves
again that Tandberg always maintains
the impressive difference in creating
sound equipment for the finest sound
re- creation that can be attained. The
Tandberg 5 goes beyond the ability of
any stereo tape recorder. It is the only
one that operates at 1v/e I.P.S. with superb tape motion. In addition to 4 -track
stereophonic recording and playback,
the Tandberg 5 is the first to offer recording and playback on four monaural
tracks. Think of getting so much from
one tape! This extraordinary recorder
has that "extra quality everything" that
unhas built the Tandberg Tradition
questionably why you can be confident
of it ... and with it ... for years of unsurpassed recording and listening
pleasure.
If you're interested in Monaural Tape
Recorders, you can be sure, too, that
nothing matches a Tandberg most remarkable performance at PA! You
haven't heard anything like it. Select
from four models -2 speeds or 3 speeds,
with or without foot pedal for remote
control operation.
and
ONLY
TANDBERG
STEREO
Records
8 Hours
-
PERFORMANCE, VERSATILITY, ECONOMY
32 Minutes
on One
-
Reel of Tape
30 to
20,000
tracks with complete facilities for 4 -track Stereo and 4 -track
Monaural recording and playback, plus
playback of 2 -track Stereo and 1/2 -track
Monaural
2 built -in preamplifiers and power
amplifiers
specially designed 4 -track record playback head and 4 -track erase head
which can erase one track or two
tracks at a time
3 speeds, 4
three operating speeds -PA,
71/2
and
response:
frequency
cycles
33/4,
and
I.P.S.
special selector switch permits 4track Stereo or Monaural recording or
playback without tape rewind
automatic tape stop prevents tape
from winding off reel at end of play
long -life motor switch for automatic
shut -off when not recording or playing
back tape
one lever control for tape start -stop,
rewind, fast forward, record -play
distinctively styled, mahogany wood
cabinet and separate "hand- tailored"
luggage case
See
Plays Back Two Track
and Four Track Tape
10
AUDIO
I
your dealer or write to:
TANDBERG
EAST 52nd STREET, NEW YORK 22, NEW YORK
MARCH, 1959
5
www.americanradiohistory.com
LETTERS
ELIMINATES NUM
thanks to special construction
and Mu Metal Shielding!
Styli for Stereo and Mono Records
SIR:
I do not understand why a 0.7 -mil stylus
should be so much less wearing on a record
than a 0.5 -mil stylus with equal tracking
force. Several of your authors mention
this. It is surely here a matter of how
much of the stylus is in contact with the
record material, which is largely a matter
of the flow of the material. Ideally speaking, with a hard record material, one should
only get a point contact between stylus
STEREOTWIN 200
magnetic stereo hi -fi cartridge
That fits all record changers
and st
tone arms
NOW
$4480 formerly $59.50
audiophile net
STEREOTWIN is the perfect cartridge
for stereo and monaural. No modifications or changes required in your
record -playing equipment, since
STEREOTWIN 200 is perfectly shielded to
eliminate hum! Instant stylus replacement. Completely compatible for both
stereophonic and monophonic reproductions. And now at a new low price!
Magnetic cartridge
.7
mil diamond stylus
transient response
within 2 db from 20 to 20.000 cps
no
magnetic pull
instant stylus replacement
fits all standard tone arms and
SPECIFICATIONS:
record changers
eliminates hum problem.
and record.
After the first mention of the fact, one
does not find reference to the fact that to
hear monophonic records with a stereo cartridge it is possible to connect the cartridge
so that the vertical component is cancelled
out and the cartridge acts as a true monophonic cartridge. What would ETC say to
the use of stereo cartridges if they were
so connected for monophonic use.
I also find that there is little technical
data on rumble filters, though of course
with stereo records they are more important than ever. This subject should be
good grist for Cdr. Harrison's mill.
P. S. HIRSCHMANN,
Rehov Hagefen,
Tivon, Israel.
:
For playing monophonic LP records,
will better results be obtained with a top grade 0.7 -mil stylus of the stereo type,
using a proper switch, or from a top -grade
-mil stylus in a monophonic pickup?
For stereo -monophonic playing, two cartridges will be used if your answer favors
the l -mil stylus for monophonic use.
1
B. BADE!, JR.,
217 N. Grant St.,
Waynesboro, Pa.
(A common question, with an iffy answer.
Actually, the Theoretical point contact does
not exist in practice-there is some de
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monophonic model.
We trust Cdr. Harrison will take notice
of the suggestion in the first letter. ED.)
More on Multiplex
SIR:
A multiplex stereo system with advantages of both Crosby and Halstead is to
transmit the sun signal on the regular FM
channel and the signal for one speaker on
the subcarrier.
This proposed system provides a complete signal for the monophonic listener
while assuring the simplest matrixing circuit for the receiver. Noise output of the
subcarrier detector is applied equally to
the two speaker systems resulting in a
minimum of listener discomfort.
IRVING D.
RICHMOND,
2230 Grand Concourse,
Bronx 57, N. Y.
(Sounds as though there might be some
merit in this suggestion. However, it does
not allow for any possibility of a narrower
band width for the subcarrier, which is one
of the things to be desired in any multiplex
system if it can be obtained without degradation of quality. ED.)
SIR:
SIR
J.
The Turntable That Changes Records
tridge is still better than the average
formation of the record material, and the
smaller the stylus the more it will depress
the record. Since the area of the contact is
the important factor, stylus force should
be proportional to the square of the radius
for the same distortion of the record sur
face. Therefore, if we reduce the stylus
radius by one-half, we should reduce stylus
force by one -quarter; a reduction from I
mil to 0.7 mil should be accompanied by a
force reduction to one -half. Pickering has
long had available a 0.5 -mil stylus which
gives better high- frequency performance on
the more recent records which have been
cut with. a V stylus -that is, without any
rounding of the point. Similarly, the Shure
Studio Dynetic was introduced with a 0.7mil stylus as standard because of the better performance -both of these being intended for monophonic records. However,
it is not likely that the 0..5- or 0.7 -mil styli
would perform satisfactorily, with respect
to record wear, with an arm or turntable
which required a stylus force of, say, 6
grams.
As to whether the stereo cartridge will
give as good performance on monophonic
records as a good mono cartridge is still
to be determined. We believe that the finest
stereo cartridges are perhaps not yet equal
to the finest monophonic cartridges, but we
also believe that the average stereo car.
Iu this listener's opinion, both Audio
and Mr. Canby are on the wrong track in
reference to the current debate of Crosby
vs. Halstead multiplex.
Instead of compromising the Crosby system by reducing the 25 -ke bandswing, why
not approach the problem of "pirating" by
making it impossible for the hone listener
with a Crosby -type converter to hear the
commercial stuff, which Mr. Crosby so
aptly labels "musical dishwater." Wouldn't
it be feasible for the commercial broadcasts to be scrambled or keyed in such a
manner as to prevent eavesdropping?
Any final decision on multiplex which
(1), prevents the listener without a converter from hearing a full monophonic signal, or (2), degrades one or both of the
stereo channels, would be a disservice to
the major portion of the listening public,
and would, in my opinion, reduce the growth
potential of FM radio which an unadulterated Crosby stereo system could bring
about.
H. S. RoBISON,
3 Devonshire Drive,
White Plains, N. Y.
(We couldn't agree more with items .1
and 2 in the last paragraph. It would appear, however, that scrambling would entail an unnecessarily high cost to the background operators, and in many areas it is
this background operation which pays the
freight for the "good music" broadcasts on
the main channels. ED.)
SIR
:
The Editor is to be commended for opening and continuing to stimulate discussion
of stereo broadcast standards by publishing
the very valuable contributions of Bert
Cowlan and Murray G. Crosby in the November issue. Should any avenue toward a
possible solution be left fallow now, the
(Continued on page 10)
AUDIO
6
www.americanradiohistory.com
MARCH, 1959
HEATHKIT
style
performance
quality
If
STEREO EQUIPMENT CABINET KIT
MODEL SE-1 (center unit)
wit soul 6.4.i
I'
MODEL SC -1 (speaker enclosure)
Shag. Wt.
u
$14995
421b,
$3995 each
Superbly designed cabinetry to house your complete stereo system.
Delivered with pre -cut panels to fit Heathkit AM -FM tuner (PT -1).
stereo preamplifier (SP -I & 2) and record changer (RP -3). Blank
panels also supplied to cut out for any other equipment you may now
own. Adequate space also provided for tape deck. speakers, record
storage and amplifiers. Speaker wings will hold Heathkit SS -2 or
other speaker units of similar size. Available in unfinished birch or
mahogany plywood.
MONAURAL -STEREO PREAMPLIFIER
KIT (Two Channel Mixer)
World's largest manufacturer of
electronic instruments in kit form
MODEL SP -2 (stereo) $56.95 Shpg. Wt. 15 lbs.
MODEL SP -1 (monaural. $37.95 Shpg. Wt. 13lbs.
MODEL C -SP -1 (converts SP -1 to SP-2) $21.95
Shpg. Wt. 5 lbs.
HEATH
COMPANY
Benton Harbor, 25, Michigan
Special "building block" design allows you to
purchase instrument in monaural version and add
stereo or second channel later if desired. The SP -1
monaural preamplifier features six separate inputs
with 4 input level controls. A function selector
switch on the SP -2 provides two channel mixing.
A 20' remote balance control is provided.
HIGH FIDELITY
RECORD CHANGER KIT
MODEL RP -3
PROFESSIONAL STEREO-MONAURAL
AM -FM TUNER KIT
MODEL PT -1
1899&
The t0 -tube FM circuit features AFC (automatic
frequency control) as well as AGC. An accurate
tuning meter operates on both AM and FM while
a 3- position switch selects meter functions without
disturbing stereo or monaural :istening. Individual flywheel tuning on both AM and FM. FM
sensitivity is three microvolts for 30 db of quieting.
The 3 -tube FM front end is prewired and pre aligned, and the entire AM circuit is on one printed
circuit board for ease of construction. Shpg. Wt.
20 lbs.
AUDIO
$6495
Turntable quality with fully au omatic
features! A unique "turntable pause" allows
record to fall gently into place while turntable is stopped. T ie tone
arm engages the motionless record, and a friction clutch assures
smooth start. Automatic speed selector plays mixed 33'3 and 45
RPM records regardless of sequence. Four speeds available: 16. 33'3.
45 and 78 RPM. Changer complete with GE -VR -I1 cartridge with
diamond LP and sapphire 78 stylus, changer base, stylus Fressure
gauge and 45 RPM spindle. Shpg. Wt. 19 lbs.
"EXTRA PERFORMANCE" 55
WATT HI -FI AMPLIFIER KIT
A real work horse packed with top quality
features. this hi -fi amplifier represents a
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damping is a true 55 watts from 20 CPS
to 20 kc with less than 2''i- total harmonic
distortion throughout the entire range.
Featuring famous "bas -bal" circuit, push pull EL34 tubes and new modern styling.
Shpg. Wt. 28 lbs.
MARCH, 1959
MODEL W7 -M
S5495
7
www.americanradiohistory.com
HIGH FIDELITY AM TUNER KIT
$2695
MODEL BC -1A
Designed especially for high fidelity applications
this AM tuner will give you reception close to
FM. A special detector is incorporated and the
IF circuits are "broadbanded" for low signal
distortion. Sensitivity and selectivity are excellent
and quiet performance is assured by a high
signal -to -noise ratio. All tunable components
arc prealigned before shipment. Your "best buy"
in an AM tuner. Shpg. Wt. 9 lbs.
"BOOKSHELF"
MODEL EA -2
12
WATT AMPLIFIER KIT
$2895
HIGH FIDELITY FM TUNER KIT
There are many reasons why this attractive amplifier is such a tremendous dollar value. You get rich, full range, high fidelity sound
reproduction with low distortion and noise ... plus "modern styling".
The many features include full range frequency response 20 to 20,000
CPS ± I db with less than I %p distortion over this range at full 12
watt output -its own built-in preamplifier with provision for three
separate inputs, snag phono, crystal phono, and tuner -RIAA equalization- separate bass and treble tone controls-special hum control
and it's easy -to- build. Complete instructions and pictorial diagrams
show where every part gocs. Cabinet shell has smooth leather texture
in black with inlaid gold design. Shpg. Wt. 15 lbs.
For noise and static-free sound reception, this FM
tuner is your least expensive source of high fidelity material. Efficient circuit design features
stabilized oscillator circuit and broadband IF
circuits for full fidelity with high sensitivity. All
tunable component; are prealigned before shipment. Edge- illuminated slide rule dial. Covers
complete FM band from 88 to 108 mc. Shpg.
Wt. 8 lbs.
"MASTER CONTROL" PREAMPLIFIER KIT
"UNIVERSAL"
MODEL WA -P2
$1975
All the controls you need to master a complete high fidelity system
are incorporated in this versatile instrument. Features 5 switch selected inputs each with level control. Provides tape recorder and
cathode -follower outputs. Full frequency response is obtained within
11/2 db from 15 to 35,000 CPS and will do full justice to the finest
available program sources, Eqization is provided for LP, RIAA,
AES, and early 78 records: Shpg. Wt. 7 lbs.
t
HIGH FIDELITY TAPE
RECORDER KIT
MODEL TR -1A $9995
Includes tape deck assembly
ampliller and roll of tape.
pre
MODEL TE -1
Stipp. /.I.
10
$3995
lbs. (Tape Preamplifier Only)
The model TR -IA provides monaural record /playback with fast
forward and rewind functions. 7yz and 31/4 IPS tape speeds are
selected by changing belt drive. Flutter and wow are held to less than
0.35%. Frequency response at 71 IPS t2.0 db 50- 10,000 CPS, at
33/4 IPS t2.0 db 50-6,500 CPS. The model TE -I record /playback
tape preamplifier, supplied with the mechanical assembly, provides
NARTB playback equalization. A two -position selector switch provides for mike or line input. Separate record and playback gain
controls. Cathode follower output. Complete instructions provided
for easy assembly. Signal -to-noise ratio is better than 45 db below
normal recording level with less than 1% total harmonic distortion.
(Tape mechanism not sold separately). Shpg. Wt. 24 lbs.
MODEL FM -3A
$2695
12
WATT
AMPLIFIER KIT
MODEL UA -1 $2195
Ideal for stereo or monaural applications, this
I2 -watt power package features less than 2%
total harmonic distortion throughout the entire
audio range (20 to 20,000 CPS) at full 12 -watt
output. Use with preamplifier models WA -P2
or SP -I & 2. Taps for 4, 8 and 16 ohm speakers.
Shpg. Wt. 13 lbs.
YOU'RE NEVER OUT OF DATE
WITH HEATHKITS
Heathkit hl -fi systems are designed for maximum flexibility. Simple conversion from basic to complex systems
or from monaural to stereo is easily accomplished by
adding to already existing units. Heathkit engineering
skill is your guarantee against obsolescence. Expand
your hi -fi as your budge! permits ... and, if you like,
spread the payments over easy monthly installments
with the Heath Time Payment Plan.
AUDIO
8
www.americanradiohistory.com
MARCH, 1959
CONTEMPORARY
CHAIRSIDE ENCLOSURE KIT
Model CE -1B Birch
Model CE -1M Mahogany
*4395
MODEL CE -1
each
Control your complete home hi-fi system right from
your easy chair with this handsome chairside enclosure in either traditional or contemporary models. It is designed to house the Heathkit AM and
FM tuners (BC -IA and FM -3A) and the WA -P2
preamplifier, along with the RP -3 or majority of
record changers which will fit in the space provided.
Well ventilated space is provided in the rear of t he
enclosure for any of the Heathkit amplifiers designed to operate with the WA -P2. The tilt -out
shelf can be installed on either right or left side as
desired during the construction, and the lift -top
lid in front can also be reversed. All parts are precut and predrilled for easy assembly. The contemporary cabinet is available in either mahogany
or birch, and the traditional cabinet is available in
mahogany suitable for the finish of your choice.
All hardware supplied. Shpg. Wt. 46 lbs.
No Woodworking Experience
Required For Construction.
All Parts Precut
&
Predrilled
For Ease of Assembly.
TRADITIONAL
Maximum Overall Dimensions:
18" W. x 24" H. x 35%" D.
IT'S EASY
.
.
.
ITS
Model CE -1T Mahogany
"BASIC RANGE" HI -FI SPEAKER SYSTEM KIT
FUN
The modest cost of this basic speaker system makes it a spectacular buy for any
hi -fi enthusiast. Uses an 8' mid -range
woofer and a compression -type tweeter to
cover the frequency range of 50 to 12,000
CPS. Crossover circuit is built
in with balance control. Impedance is 16 ohms. Power rating 25 watts. Tweeter horn rotates so that the speaker may
be used in either an upright or
horizontal position. Cabinet is
made of veneer- surfaced furniture -grade plywood suitable
for light or dark finish. All wood
parts are precut and predrilled
for easy assembly. Shpg. Wt.
AND YOU SAVE UP TO
WITH DO -IT- YOURSELF HEATHKITS
Putting together your own Heathkit can be one of the most
exciting hobbies you ever enjoyed. Simple step -by -step instructions and large pictorial diagrams show you where
every part goes. You can't possibly go wrong. No previous
electronic or kit building experience is required. You'll
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having done it yourself.
*3995
MODEL SS-2
Legs: No.
DIAMOND STYLUS HI -FI
PICKUP CARTRIDGE
91 -26
1
"RANGE EXTENDING" HI -FI
SPEAKER SYSTEM KIT
The SS -IB employs a 15' woofer and super
tweeter to extend overall response of basic
speaker from 35 to 16,000 CPS ±5 db.
Crossover circuit is built in. Impedance is 16
ohms, power rating 35 watts. Constructed of
3/4' veneer- surfaced plywood suitable for light
or dark finish. Shpg. Wt. 80 lbs.
SS -2
MODEL HH -1
MODEL SS -1B
195 lbs.
COMPANY
L
pioneering
a $
C/
14,-11-yourself"
electronics
livery charges collect.
All prices F.O.B. Benton
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posit is required on all
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subject to change with.
out notice.
AUDIO
$29995
either African mahogany or white
birch suitable for the finish of your
choice. All parts are precut and pre drilled for easy assembly. Shpg. Wt.
Enclosed find S
Please enclose postage
for parcel post- express
orders are shipped de-
Describing over 100 easy -to -build
kits in hi -fi, test, marine and ham
radio fields. Also contains corn plete specifications and schematics.
26 lbs.
lb. $4.95
The startling realism of sound reproduction by the Legato is achieved
through the use of two 15' Altec
Lansing low frequency drivers and a
specially designed exponential horn
with high frequency driver. The special
crossover network is built in. Covers
25 to 20,000 CPS within ± 5 db. Power
rating 50 watts. Cabinet is constructed
of 3/4' veneer- surfaced plywood in
HEATH
SEND FOR FREE CATALOG
3
LEGATO HI -FI SPEAKER SYSTEM KIT
*8695
MODEL MF -1
Replace your present pickup with the MF -I
and enjoy the fullest fidelity your library of
LP's has to offer. Designed to Heath specifications to offer you one of the finest cartridges
available today. Nominally at response from
lb.
20 to 20,000 CPS. Shpg. Wt.
*9995
Shpg. Wt.
T
BENTON HARBOR 25, MICH.
bsidiary of Daystrom, Inc.
Please send the Free Heathkit catalog.
name
address
city
8.
state
QUANTITY
ITEM
MODEL NO.
PRICE
9
MARCH, 1959
www.americanradiohistory.com
LETTERS
(from page 6)
Sound
Talk
by Dr. W
T.
opportunity may be lost forever, for precedent is a cruel tyrant indeed.
Industry -wide discussion is especially
needed in this era of influencing interested
commissioners. The F.C.C. will need all the
help it can get from an informed public
Fiala
Chief Physicist
LOUDSPEAKER DISTORTION AT
LOW FREQUENCIES
Lord Rayleigh, in his famous "Theory of
Sound;' had shown that the acoustic power
generated by a cone in an infinite wall is
proportional to the square of the frequency
and to the square of the air volume displaced per second. This relation indicates
that at low frequencies considerable amplitudes are required to produce acoustic
power. A 15" cone speaker, for example,
has to move approximately one-half inch,
peak to peak, in order to generate one
acoustic watt at 40 cps.
However, it is not sufficient to design a
speaker which is only able to move with
the required amplitude. In order to avoid
distortion, it is also necessary that this
movement follows exactly the driving current in the voice coil. To achieve this, the
suspension system has to be linear for the
required amplitude. This means that the
displacement of the cone has to be proportional to the driving force produced by the
voice coil or, more specifically, if the
transfer characteristic is plotted in linear
coordinates, it should be represented by a
straight line so that each doubling of the
force on the cone also doubles the displacement. This force, generated by interaction of the current in the voice coil and
a magnetic field, must also be proportional
to the voice coil current. Thus, each doubling of the voice coil current should double
the driving force. When these two requirements are met, the displacement of the
cone is proportional to the driving current
in the voice coil. In other words, the trans-
fer characteristic of the speaker, which
relates cone displacement versus voice coil
current, has to be linear.
Present day technology and carefully controlled assembly techniques make it practical to build linear suspension systems for
large excursions. The use of sufficient magnet to produce a long enough uniform
magnetic field so that the voice coil always
remains in that field for the required amplitude will secure the necessary linear forcevoice coil current relation.
ALTEC LANSING controlled linear
excursion speakers are designed, manufactured, and even optically tested to meet all
these linearity requirements.
Write for free catalogue: ALTEC LANSING
CORPORATION, Dept. 3A, 1515 S. Manchester Avenue, Anaheim, Calif., 161 Sixth
Avenue, New York 13, N. Y.
12.47
opinion.
The Editor's questioning that the public
interest, convenience, and necessity are well
served by many AM stations, or for that
matter, network TV, is extremely well
taken. Certainly it should be the responsibility of the licensees to lead the public
taste rather than to follow. Few, very few,
do so, some even attempting to rise to BBC
standards in this respect. But fortunately,
so far, FM licensees tend on the average to
discharge this responsibility more diligently
than others. It is this precarious situation
that Cowlan and Crosby would not disturb.
It seems to me that the critical element
toward decay in the broadcast picture are
the advertising agencies, both local and
Madison Avenue. They tend to promulgate
both explicitly and implicitly, pathological
values of a romantic, infantile, fantasy
world, sterile and materialistic. The Editor's original point of view is no doubt explained by his need and desire to keep the
agencies happy, not as suggested by Crosby,
lack of engineering data. The Editor's reference to "presumed public ownership of
the air" is rhetorically deferent to the same
interests; as public ownership is firmly
established and universally recognized.
Personally, I am thoroughly in accord
with the statement of Cowlan of WBAI.
Also, that 69- per -cent range mentioned by
Crosby would be fatal to San Diego listening, producing a monopoly in the quality
listening field. It should be noted that in
addition to FM -AM, and now multiplex,
there is in the Los Angeles area FM -FM
stereo, in which two co- operating licensees
transmit the A and B channels. Before
closing discussion, let's complete the roster.
Russ
LINTON,
2524 44th St.,
Electrical Engineer,
San Diego 5, California
Small -Box
Loudspeaker Systems -again
SIR:
In answer to Mr. Villehur's comments
February) it is possible to design a high -compliance, long- travel woofer
for both small and large boxes. We recommend Jensen P12NF and P15LF with bellows suspensions, voice coils r in. longer
than airgap, and symmetrical magnetic
field, for small, medium, or large enclosures.
Rather than restrict excursion and thereby
reduce output, it is preferable to let the
cone move the required distance. It must
move the same distance for a giren loud
mess at a given frequency, regardless of
(LETTERS,
size with a closed box. The use of a "protective device" such as higher resonance
to reduce distortion will be defeated if bass
boost is used to overcome resulting loss in
output.
A better method of reducing excursion
and distortion without reducing output is
to vent the box. A properly proportioned
vent increases speaker damping without
losses in bass because the vent also radiates
sound. The linear vent elements and reduced voice -coil excursion greatly reduce
distortion. The experiment of converting a
10
good high -compliance vented speaker system to a closed box system demonstrates
the principle. With single tones from
slightly below woofer resonance to an
octave and a half above, the cone movement increases as the vent is closed. A drop
in bass output is observed, ranging from
slight or imperceptible for a small box to
many db for a large one. Short of horn
loading, we know of no better way to limit
excursion at lower frequencies, without
losing output, than to open the vent again.
There can he no question of superiority
of the large box in vented design. In the
closed box, Mr. Villchur answers the "more
bass" part by saying the small box limits
excursion below resonance, at constant in-
put. Theory and practice compare distortions as follows:
Large box delivers more low bass per
watt, so system distortion is lower, less
amplifier power being required.
2. With the cone having to move a. fixed
distance in either case, harmonic distortion is the same.
3. Larger box delivers lower system Q,
all else being equal, so transient distortion is lower.
1.
Dr. Beranek's suggestion of Q of 1.36
or less was based on tests under certain
conditions which may not be universal. In
the same text quoted, he also says that Q
of 0.5 gives critical damping, and that it is
not known just how low Q should be.
It would appear to be better to start with
critical damping, and raise Q if desired by
series resistors or other means. Then the
optimum Q is possible for any condition.
PHILIP B. WILLIAMS and JAMES F. NOVAK,
Jensen Manufacturing Co.,
6601 S. Laramie Ave.,
Chicago 38, Illinois.
AM Detection
SIR:
An erroneous statement regarding half wave detection of AM signals was made
in Mr. Canby's AUDIO ETC. column in the
December issue. In actuality, all home-type
"standard" AM receivers do detect both
sidebands of an AM signal, whether or not
the detector circuit is half -wave or full wave.
Chief Engineer,
Radio Station WFMT,
22. N. La Salle St.,
Chicago, Ill.
DONALD HALFORD,
IF YOU ARE
Circulation Department
RADIO MAGAZINES, INC.
Box 629, Mineola, N. Y.
P. O.
AUDIO
www.americanradiohistory.com
MOVING
Please notify our Circulation Department
at least 5 weeks in advance. The Post Office
does not forward magazines sent to wrong
destinations unless you pay additional postage, and we can NOT duplicate copies sent
to you once. To save yourself, us, and the
Post Office a headache, won't you please
cooperate? When notifying us, please give
your old address and your new address.
MARCH, 1959
Am perex
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available for off- the -shelf deliveries in any quantity.
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ECC 82 /12AÚ7- Low -gain dual triode with low hum,
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16v) version
noise and microphonics. Replaces the 12AU7 without circuit changes.
ECCI3 /12AX7- High-gain dual triode with low hum,
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-
High -gain triode -pentode
hum, noise and microphonics.
ECFIO/68L 8
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RF AMPLIF 1ER TYPES
6D1I /ECCIe -Frame grid, sharp cut -off twin triode.
Particularly suitable for cascode circuits, RF & IF
amplifiers, mixer & phase inverter stages. Features high transconductance and low noise.
6ESI- Similar to 6D18 /ECC88. Has remote cut-off
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6ER5 -Frame grid shielded triode with remote cutoff characteristics. Suitable for RF amplifiers in
TV & FM tuners. Features high transconductance
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1ECC85 /6A88 -High gain dual triode for FM tuners
with shield between sections for reducing pscillato, radiation.
EBFI9 /6DCI -Duo diode -pentode with remote cutoff characteristics. Suitable for RF & IF amplifiers.
ECFIO /6BL8 -High gain triode-pentode for RF amplifiers.
RECTIFIE R TYPES
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Indirectly heated, full -wave rectifier
EZ80 /6V4
with 6.3 v, 0.6 amp. heater, 90 ma. output capacity and 9 -pin miniature construction.
Indirectly heated, full -wave rectifier
with 6.3 v, 1 amp heater, 150 ma. output capacity
and 9 -pin miniature construction.
EZ 111 /6AC4-
Detailed data and applications engineering assistance available from Semiconductor and Special
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VOLTAGE AMPLIFIER TYPES
EF86/6267- High -gain pentode with exceptionally
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0
until he begins to find a good resting place
that joins the two pictures comfortably.
(Be sure the slide is in all the way, the
two pictures aligned ; better try it yourself
first, to he sure.)
Then when conjunction is accomplished
you get that far -point out the focus
knob and let him play with it. After that,
don't move anything. And if the pictures
just won't join, or the person starts saying
how lovely, with that vague, uneasy smile
that says trouble is being concealed, just
quietly change the subject. Maybe it's time
for dinner; or have you seen my new stereo
iii -fi system yet? Pardon me-I mean heard.
No use going on if the patient evinces
symptoms of anastereoitis.
-if
UD'
0
éjdward ratnall Canby
THE OTHER KIND OF STEREO
\\IT
IS WITH
a great deal of pleasure
that I read your recent article pertaining to stereo photography. I, too,
am the owner of a stereo camera. .
"I read with
interest, on p. 10 of
the January AUDIO, of your success with
stereo projection. I have enjoyed stereo
pictures for years
but have tried unsuccessfully to get a recommendation, even
from the Eastman Kodak Company, on a
projector. I think you would please many
AUDIO fans if you would tell us what equipment you use . . .
"So you also are keen on colour photog-
...
...
raphy!
(This from England.) I'm just
starting to play with stereo pictures . .
I've not yet got around to projecting
them
...
"
Well, there you have a few yelps of
delight from an obviously frustrated minority and, you see, it's just as I said. Stereo
photography, big biz has decided, is not
for the Great American Public, and so,
down with it; the People say, NO. But
some of then, in small, anguished voices,
still say yes. With a pious hope that our
own stereo sound will never, but never, be
reduced to this sad state (as per the
January AUDIO, ETC.) I bow to the inevitable, invoke my useful escape clause
that "etc" in its alternative meaning of
et cetera -and herewith toss a few ideas to
the ravening hordes of stereo camera bugs.
I'm probably the only guy left who has a
kind word to say in print for stereo. Stereo
pictures, that is. And I am dead -certainly
the only person who has ever come out for
stereo projection in a magazine about
audio. Deny that if you dare.
-
1. VIEWERS
Projection, in fact, is what's on my mind
but first a bit of foreground. Anybody can
look at stereo through a viewer, and get the
best possible stereo in this imperfect world.
Nothing can beat it. Only those who have
(a) one eye or (b) two eyes that habitually don't operate together (one goes psychologically blind) will find themselves
constitutionally unable to get a stereo
effect.
The second category, I've found, includes
a remarkably large number of souls, most
of whom don't even know they lack stereo
vision. They always exclaim how pretty the
pictures are and it's only when you quiz
them very specifically about certain perspective details, like say, a branch of a tree
that seems to be hitting you in the eye in
the foreground, that you uncover a certain
vagueness. Pretty soon you begin to suspect that something isn't right, but it is
amazing how hard it is to pin down the
stereo -less pair of eyes. It's like color blindness, which even in this day of red and
green traffic lights can go unsuspected for
an astonishingly long slice of life in many
people.
I usually shut up and say no more when
I begin to realize that a given person
simply is not seeing stereo. That's the only
tactful thing to do. After all, if they can't
tell the difference, why he brutal. Some
stereo newcomers are so very polite that it
may take you a dozen pictures to find out
that they are actually seeing everything
double, and unregistered. These nice people,
after oohing and anteing about the beautiful
photography and the lovely colors for ten
or fifteen minutes, are apt to disclose,
purely incidentally, that of course they are
closing one eye -aren't you svppo.sed to do
that? "Why, I see double if both eyes are
opened. I thought it was so you could rest
one eye at a time. . . ." Amazing what
sheeplike virtues some people have!
And no wonder stereo photography was
sold down the river by the big operators.
Even sheep protest, eventually.
Ink -blue
The only proper type of viewer is that
which has a built -in house- current light
supply, via a small 80 -volt bulb and a
rheostat to adjust the amount of light. The
bulb may be small but its light is still
enormously more powerful that that of the
battery -powered viewer light, the flashlight
type. Once you've used the plug -in house
current system, you'll never go hack to
batteries except for emergencies or extreme
portability.
There's a major trouble with the plug -in
light.. Its color is wrong. Too yellow. (The
flashlight bulb is beautifully white, at
least for the first few minutes, before it
begins to run the batteries down). When
you reduce the light's brightness via the
silly "volume control," the color gets yellower still. The only proper rheostat position is wide-open, at full voltage. I have a
simple "solution" for this, speaking quite
literally. Take out your bulb and dip it in
blue ink, let it drip off and dry. Then you'll
have a fine, soft, blue -white light that is
exactly right.
True, the bulbs blow sooner (you'll need
a half -dozen extras on hand) and the ink
tends to turn dark. But you can wash it off
and start again any time. With the inky
bulb you'll finally get away from those
yellow- orange sky effects that mar stereo
viewing in so many viewers. (Why don't
they make a blue bulb? Too much trouble,
I guess.)
You'll note two adjustments on viewers,
that for the separation of the lenses and
that for focus. They can throw any new
user into a tizzy, unless you demonstrate
therm one at a time. Start with a fixed
focus-i.e., don't mention it at all -and
have the viewer wiggle the separation lever
Details
The viewer, one- person -at-a -time, is the
only way really to see stereo. The viewed
image is far superior to the projected
image in a number of ways. It is sharper
and clearer, but also, more important, it is
relatively much larger; it fills a far greater
area of the visual field. A stereo picture
inside a. viewer is, let's say, roughly equivalent to a nine- foot -square image on a
screen at about ten feet. Huge. Details are
infinitely better in the resolution via the
viewer than via projection, and (with
Kodachrome) details are the very essence
of good stereo. To be able to recognize a
person at a distance of a quarter mile via
a stereo viewer is really something, but the
magnification and the sharp detail (via a
good lease) makes it quite possible. Saine
with distant mountains, pin -point houses
across a wide valley, distant signs, etc.
Incidentally, I use only Kodachrome.
Grainy color films are taboo in stereo -the
magnification (via viewer) is enormously
too great and you can practically count the
dots. Kodachrome has no dots; it is a (lye
picture and, if I'm right, has practically
infinite detail resolution. It is absolutely
amazing to look at a Kodachrome 35 -mm
picture with the naked eye and see how
incredibly tiny are some of the clear details
that can be seen and resolved via the huge
viewer magnification.
Incidentally too -while I'm at it
use
Kodachrome not because it gives a true
color value but because the exaggerated
Kodachrome colors are absolutely first rate
for dramatic emphasis in the peculiar stereo
visual medium. This is an interesting point
and has a direct analogical relation to the
sanie thing in sound recording. In stereo
-I
pictures, there are many missing elements
-motion above all, but also the more subtle
sense of actual happening, of life itself,
including the accompanying sounds. The
picture has depth, but is still a picture. For
emphasis and dramatic force, then, a stereo
picture -any sort of picture-must make
up for the lack by plugging, exaggerating
what it has. That's where the art comes in.
Same thing in recording.
Kodachrome rightly plays up color values
(though with good color balance) and
legitimately gives a heightened sense of
draina to good stereo photography. In
the saine way, close -up mike technique,
blown -up volume on solos, on opera singers,
solo instruments with orchestra, distorts
"reality" but adds legitimate drama and
force to reproduced sound, for a truer
emotional projection of the musical effect.
So I'm all for Kodachrome's color, though
many people deplore it, just as I am all for
dramatic mike techniques in recording,
though they are far from literal- minded.
Back to the stereo viewer. It is best for
one major reason above all others
is
the only form of stereo viewing that does
not distort the optical values of the pic-
-it
AUDIO
12
www.americanradiohistory.com
MARCH, 1959
NEW STEREOPHONIC EQUIPMENT
HF85: Stereo Dual Preamplifer is a complete stereo
control system in "low silhouette" design adaptable to
any type of installation. Selects, preamplifies, controls
STEREO
AND
M ONAURAL
any stereo source -tape, discs, broadcasts. Superb variable crossover, feedback tone controls driven by feed.
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on unmeasurable even at high output levels. Separate
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Selector permits hearing each stereo channel individu.
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monophonic play. Full -wave rectifier tube power supply.
5- 12AX7 /ECC83, 1 -6X4. Works with any 2 high -quality
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HF50, HF60. Kit $39.95. Wired $64.95. Includes cover.
the
experts
say...
HF81: Stereo Dual Amplifier-Preamplifier selects,
amplifies & controls any stereo source tape, discs,
broadcasts -& feeds it thru self- contained dual 14W am.
plifiers to a pair of speakers. Monophonically: 28 watts
-
for your speakers; complete stereo preamp. Ganged level
controls, separate focus (balance) control, independent
full -range bass & treble controls for each channel.
Identical Williamson -type, push-pull EL84 power amplitiers, excellent output transformers. "Service Selector"
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internal power amplifiers while other preamp-control
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in HI -FI
the best buys are
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NEW HF65: superb new design, Inputs for tape head,
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MONAURAL POWER AMPLIFIERS
World- famous
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-
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a
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-
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o
o
HF30: 30 -Watt Power Amplifier. Kit $39.95. Wired
$62.95. Cover E-3 $3.95.
NEW HF22: 22 -Watt Power Amplifier. Kit $38.95.
Wired $61.95. Cover E-2 $4.50.
NEW HF14: 14 -Watt Power
Wired $41.50. Cover E -6 $4.50.
Amplifier. Kit $23.50.
MONAURAL INTEGRATED AMPLIFIERS
(use 2 for STEREO)
HF52: 50 -Watt Integrated Amplifier with complete
"front end" facilities 8 Chicago Standard Output Trans.
former. "Excellent value " -Hirsch -Houck Labs. Kit $69.95.
Wired $109.95. Cover
E.1
$4.50.
HF32: 30 -Watt Integrated Amplifier. Kit $57.95.
Stereo Preamphher HF85
Wired $89.95. Both include cover.
HF2O: 20 -Watt Integrated Amplifier. "Well -engi.
neered"
Stocklin, RADIO TV NEWS. Kit $49.95. Wired
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-
HF12: 12 -Watt Integrated Amplifier. "Packs
F
V V
a
wallop " -POP. ELECTRONICS. Kit $34.95. Wired $57.95.
SPEAKER SYSTEMS (use 2 for STEREO)
11E52: Natural bass 30 -200 cps via slot -loaded 12 ft
split conical bass horn. Middles & lower highs: front rai:.
anon from 842" edge-damped cone. Distortionless sp :ke.
shaped super -tweeter radiates omni -directionally. F at
ra
Stereo
Amplifier Preamp
HF81
c
Bookshelf
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-
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HFS1
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45-20,000 cps, useful 30- 40,000 cps. 16 ohms. HWD
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FM TUNER
HFT90: surpasses wired tuners up to 3X its cost. Prewired. pre -aligned, temperature -compensated "front end"
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"0
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-
.
T
-
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Monaural Power Amplifiers:
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(use 2 for Stereo)
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Send FREE literature & name of neighborhood EICO dealer.
NAME
_.
ADDRESS
CITY
STATE
..
Over
1
MILLION EICO instruments in use throughout the world.
In New York hear
AUDIO
J
"The EICO Stereo Hour," WBAI.FM, 99.5 mc, Mondays, Thursdays and Saturdays, 7:00 P.M.
MARCH. 1959
13
www.americanradiohistory.com
GRADO
"Truly
tures. It sees virtually what the camera
saw, the depth and width in proper relation, and this even though in some cases
the point of infinity-the sky, or back ground-is actually at a distance of only
six inches or so. In effect, you look at a
small model of the actual scene in these
cases; but it is an accurate model with the
basic spatial relationships essentially correct from side to side and front to back,
give or take a bit of false curvature. In a
viewer rightly built and rightly used the
infinity point for your eyes is at infinity,
and all nearer points are very nearly where
they should be. Your "model" is as large
as life. (Differences between camera configurations and viewer optics account for
these effects.)
Antisocial
the
world's
So-today's big question -why project?
Why, if projection fuzzes up the details,
grossly distorts the spatial effect most of
the time, gives far too small a picture, requires messy glasses that cost too much
(Polaroid's tight little monopoly) and
generally hurts the eyes beyond bearing
why bother?
For only two reasons. One is overpoweringly important. Stereo projection is social.
Two or more people may enjoy a picture at
the same time. I've coped with as many as
sixty.
Viewer stereo is strictly antisocial. One
person at a time, exclusive, solitary
just a plain nuisance, when several people
are trying to get into the act. If you've
stood next to a joyful friend, buried in
your stereo viewer, who keeps shouting
"Oh, and what's that little thing up there,
and who's this, down in the right hand
corner?" when you haven't the faintest idea
what picture is being looked at, you'll know
what I mean.
Or if you've seen a flock of avid souls
-
finest..."
-or
STEREO CARTRIDGE $49.50
COMPATIBLE WITH
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tearing your pictures apart, pushing them
in and out of the viewer, upside -down,
STEREO TONE ARM
$29.95
Finest Walnut Wood
4
Wires and Shield
backwards, reversed, greasy fingers always
squarely on the Sim surface, dropping slides
on the floor and stepping on them in their
eagerness to be next in line
well, that's
antisocial viewing. It's anti -you, more than
anything else. It hurts.
So stereo picture makers tend to develop
into hermits. They retire to a safe, lonely
place and lose themselves happily in their
solitary hobby. Wonderful, but not for
parties. Even one extra is trouble enough.
I have two suggestions here -before I get
to a second pro-projection argument. First,
write brief captions on your slides, and do
it on the slide face that must be towards
your eyes. Make then short, readable,
simple. It's hard enough to get people to
hurts
look out of their viewer anyhow
the eyes; the quick change from the inner
infinity focus to the outer close -up is tough
on most people and they won't read your
titles at all unless prompted. But if you
say to them, "Just put the slides in with
the captions facing you and right -side -up"
-then they'll more or less have to read
them. And you'll have a minimum of upside down, backwards pictures.
Don't write "View towards the Southwestern corner of the Sierra Madre range,
taken from our little summer cabin on the
slopes of Mount Dinkydoodle, July, 1958."
(You won't have room anyhow.) But compress: "Sierra Madre. Cabin. 1958." That
does it.
Secondly, if you are showing pictures to
a friend in person, the thing to do is to
have your own viewer (that's where my old
battery- powered viewer comes in handy).
Look at each picture yourself first, in the
viewer ; then pass it on to your friend with
its image fresh in your mind. This works
...
-it
GRADO
LABORATORIES. INC
4614 7th Avenue Brooklyn 20, New York
Export- Simontrice, 25 Warren St., N.Y. C.
wonders. You can even do it with two
people, in tandem, if you hold back each
new picture until both have seen the preceding one.
2. PROJECTION
To return to where I was -the second
good reason for stereo projection is utterly
simple. For all its faults, with all its grave
difficulties, it can be made to work
you
are lucky. You can be social, and you can
do it successfully. You can entertain from
six to sixty simultaneously and emerge with
a good passing grade of blessings and a
minor proportion of curses, plus a few
blissful sleepers- somebody always takes
advantage of the darkness for a quiet
snooze. If stereo projection works at all,
it's worth the time and trouble.
But, boy, do you have problenns en route.
The first is to get a stereo projector over
the loud objections of the photography
dealers, who will tell you, of course, that it
is hopelessly impractical and they wouldn't
touch a stereo projector with a fifty -foot
pole. The second is to get a stereo screen,
which must be silvered, since beaded screens
will not work. The third is to get stereo
glasses. Plastic ones, fragile as air, a
blasted nuisance at best and they cost
around 20 cents a pair. I use 'em. Glass
ones cost a mere $3 or so apiece, which will
put you in the broke category before you
even get started. I have one glass pair
for myself. At least it doesn't fall off my
nose when I'm trying to work the projector.
The rest are plastie, some of the clip -on
type, some entirely frameless (wear your
right arm out holding 'em
use these on
kids) and a few with plastic side -arms that
keep falling off. Phooey! They do make
things hard for you.
Whether you can still buy this sort of
equipment, as things now stand, I don't
know. When a commercial boomlet like
stereo collapses, it busts wide open. (Again,
keep my moral in mind.) Maybe you can't
find any of it and the discussion is academic. But the chances are that you'll find
what you want if you persist. The reputable
stereo makers -those from the pre -boom
days-still make cameras, notably the
Stereo Realist people, and if you look hard,
and brave the dealers' displeasure often
enough, you'll locate the rest even if it has
to be in the second hand market.
My first stereo projector, a pure boom
product and a disgrace to any industry
(like some of our present gimcrack stereo
phonographs) was nearly a total flop. It
was an outrageously crude bit of expensive
gadgetry. For $100 or so you got a shaky
pair of 300 -watt optical systems in a giant
framework, intended tantalizingly to project stereo on a screen or, via a reflector,
onto a rear -facing ground glass about a
foot square. The ground glass was useless
(too small for good viewing, even by one or
two people) and the machine itself was so
flimsy that if you picked it up too hastily
the frame buckled and the ventilating fan
blades sideswiped their crude mountings
with a screetch. It was pinned together
with those little flat pieces of metal split
in the middle that pass for nuts in gimcrack construction. What's more, 300 watts
per "channel" was not enough for projection (with those lenses, anyhow). And the
-if
-
-I
picture adjustment controls promptly
stripped their gears, letting one picture
suddenly drop down a foot on the screen
each time a cog slipped.
But I had seen possibilities (I must
have been the only person who did). I went
forth again, licking my wounds, and got
me a real prize. The Nord stereo projector,
costing me half as much, was smaller,
neater, lighter, with two 300 -watt bulbs and
AUDIO
14
www.americanradiohistory.com
MARCH, 1959
plenty of screen illumination. (You need a
lot because of the double loss in the two
pairs of Polaroid filters, one in the projector, the other in the glasses you wear). It
was solid, rigid, adequately ventilated and
with good controls-an excellent machine.
Unfortunately, it was being discontinued.
The stereo boom was already about to die.
Just in case, the Nord stereo projector was
made by the North Star Specialties Co. of
Minneapolis. Maybe you can dig one up, or
persuade the company to turn out a few
more. This was a fine example of a legitimate consumer product orphaned, so to
speak, by the ruthless overexploitation that
killed the stereo boom. We could see the
same in stereo sound.
My only complaint about the Nord is
that I haven't figured a way to operate it
without getting a blast of hot air in my
face from the ventilating slats on top
not to mention a bright beam of light.
Maybe it's just because I'm left handed. I
don't mind too much, as long as my guests
are happy with the pictures.
Glasses? I offer you little hope, but
maybe you can locate some in one or another store. I keep picking them up, a few
at a time. They still sell, here and there.
If you're desperate, you can stage a raid
on one of the current revivals of those
dreadful 3 -D movies ( "The House of Wax"
-was that one?) and collect the glasses
they pass out there. Or you can always get
the $3 glass models.
Screens? No problem except in cost.
Silvered screens aren't hard to get. But be
sure to get the biggest screen you can
possibly afford. This is vital for stereo
projection. I don't recommend any stereo
projection on a screen less than 50 inches
square. That's big, though bigger is even
better. You can probably get a "atereophile
net" discount if you're lucky, about as in
the audio field. I did.
-
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Depth Distortion
And
so- stereo
projection. First of all,
you must understand that the stereo picture
on the screen is variously distorted, at
times to an almost ludicrous extent. The
optics involved are just plain cockeyed.
l buy ANYTHING,
I've got to have a
Before
Not easy to figure out in detail for most of
us, but one thing is immediately clear as
you move about your stereo room. There is
a single theoretical point where distortion
is reasonably minimum and that is the spot
where you are as "close" to the picture as
you would be inside the stereo hand viewer.
A nine -foot picture at ten feet -or a fourfoot picture at about five feet, roughly
speaking! All other, more distant positions
reason, so...
what's so
good about
offer compromises, and it isn't just a matter
of brightness and image -size, either. Distortion of perspective is fantastic.
As you move away from the stereo
screen, the sidewise dimension seems to get
smaller. So does any screened picture. The
further back you sit, the smaller the picture.
Now in the conventional projection, you
are dealing only with the two fiat dimensions and the entire picture on the screen
is reduced strictly in proportion. The only
distortion you find is the relatively slight
effect of watching your pictures from one
side, at an anglo. Not too serious until the
angle becomes acute, as we know from
movie theatre experience. In fact, the main
practical difficulty is a loss of brightness
in the image. We can take the sidewise
distortion aspect without even noticing it.
But stereo projection is utterly different. It involves the third dimensiondepth. And in the projection, that dimension never varies in apparent measurement,
regardless of your distance from the
screen! As you move back in the room, the
AUDIO
Audiotape?
MARCH, 1959
15
www.americanradiohistory.com
COMING
To Your City
...
sidewise and up -and -down size of the picture decreases, but the depth remains
exactly the same.
Therefore, a stereo picture from a distance has a violently distorted and grossly
exaggerated depth. By "gross' I mean n
lot. For if your picture is reduced (as you
see it) to one quarts size, the depth
dimension is relatively quadrupled. A picture of a square plot of grass shows as an
oblong, four times as long in depth as in
width -and a city block is four blocks
long. Nearby backgrounds, recede to near -
infinity, foregrounds are monstrous.
I'll never forget my first stereo projected picture, in a large lecture hall! It
was of the Taj Mahal, and the ratio of
dimensions from where I sat was about
1:16. The photo showed n huge, wide
plaza that stretched about ten miles back
and at the far curl was a tiny little building as big as your thumb. That projectionist didn't have the faintest idea what
HIGH FIDELITY
he was doing.
and HEAR the latest in STEREO -HIGH FIDELITY
from leading high fidelity manufacturers ...
SEE
Don't miss these public showings
of Hi -Fi Equipment . . . from
the most economical units for the
budget -minded to spectacular
home music theatres
com-
...
pare and enjoy them all.
*Complete Hi -Fi Systems and
Components.
- - - --
Pre -Amplifiers
FM-AM Tuners
Turntables
and Record Changers
Phono
Cartridges
Microphones
Music Control Centers
Speakers.
*Speaker Enclosures and Equipment Cabinets
Finished and
Assembled or Do- It- Yourself
Kits.
*Amplifiers
THREE FULL DAYS OF CONTINUOUS DEMONSTRATIONS
FROM
1
March 6, 7, 8
March 20, 21. 22
April 3, 4, 5
P.M. TO 10 P.M. FOR EACH SHOW
RIGO SHOWS 1959
Denver
Cosmopolitan
Baltimore
Lord Baltimore Hotel
Penn -Sheraton Hotel
Pittsburgh
ADMISSION 75e
RIGOEnterprises
Inc.
500 N. Dearborn, Chicago 10, III.
Close -up Window
So you will begin to see where all this
leads to. If you are to have something
near a. 1:1 relationship between the dimensions in your picture, you must be really
close to the screen, so that the sidewise
dimension is big enough to match the
unchanging front -to -back one. As I say,
that means right down in front. Or, alternatively, further back, with a LARGE
screen, the projector far enough away to
fill it to the maximum. You must at once
throw out all your ordinary conceptions of
picture projection, start thinking from
scratch. In this medium, you don't look at
the screen; you look through it-or sometimes in front of it.
Since you look through the stereo screen,
this immediately poses another new conception. It is, of coarse, n window, not n
flat surface. The window concept is essential in your stereo thinking.
\Tow, how big must a window be, to see
out of? If you will visualize for yourself
the "size" of an actual window, related to
your own inner field of vision, you'll see
at once that an ordinary home movie
screen, maybe three feet on a side and ten
or fifteen feet away, is like looking outdoors from your living room armchair
through a six -inch hole in the wall, more
or less. Your overpowering need in such
a circumstance (given a pretty view to look
at) is to get up closer, make the window
seem bigger. Or to end a larger hole in
your wall and stay in the same place.
One odd feature of this aspect. You'll
find that you can walk right up to a
stereo screen and look at parts of the
picture (into, I should say) from only two
or three feet away. The only limitation is
the graininess of the screen surface and
the fuzziness of the projected image itself.
This is due to a curious psychological fact.
If the depth dimension is /ex* than the
sidewise one-if the picture is wider than it
is-deep-you nre not aware of distortion.
We are entirely used to this situation. We
see it as a sort of low- relief effect, a step
between normal depth and no depth at all,
i.e., the ordinary "flat" picture. We accept
partial depth and, indeed, find it very
natural and satisfactory. But ,just try a
wee bit of exaggerated depth and your
eye goes crazy. Dreadfully distorted!
-Which only goes to show that in this
particular area, as in our own area of
reproduced music, the objective facts of
"hi-fi" reproduction must always be tempered by the strange interpretations of the
human mind. If it seems good to us, then it
(Continued
AUDIO
16
www.americanradiohistory.com
on.
page 65)
MARCH, 1959
easily assembled
in half an hour with
no special tools...
Now for the first time you can get a Thorens
TD transcription turntable in kit form
big savings to you.
-at
And these precision "TD" units
... completely assembled
It's the new TDK -101 featuring the same
precision Swiss craftsmanship that made
the now- famous TD-124 an immediate success on the American market. Just examine
the mirror -finished machining on this kit
turntable (or for that matter on any of the
Thorens "TD" units) and compare with that
of any other make of turntable. You'll see
the reason for the TDK's extremely low
rumble, wow and flutter. See the TDK -101,
newest member of the TD family of fine
turntables, at your Thorens hi -fi dealer's.
Features:
Same compliant belt- plus -idler drive as on
more expensive TD units; provides complete
motor isolation. Single, retained, ball-thrust
bearing, plus mirror-finished main bearing.
for absolute minimum of rumble, both vertical and horizontal -so necessary for stereo.
Single -speed 33%. Adjustable speed (±3%,
a total of about one musical semitone).
Built -in strobe allows setting to exact speed.
Automatic disengagement of idler when unit
is switched off. Drive mechanism completely
enclosed -no "string" belts or external belt
shields. Accessory wooden base is available
in walnut, blond, or mahogany; $9.00 net.
TD -124. Absolute tops
for stereo or mono rec-
ords
quietest.
dK
smoothest, most exact.
111/2 lb. table; clutch
for fast. noise -free starts
with needle in groove.
4 speeds, all adjustable
(t3 %) for perfect pitch; built -in illuminated
strobe; built -in level All assembled TD turntables are 100% tested electronically and aurally for wow, rumble and flutter before shipment. $99.75 net. Base $9.00.
TD -184. This
4 -speed
high -quality turntable
with integral arm has
same precisionma- /r
chined adjustable speed
drive as ThorensTD-124.
Semi -automatic operation -one dialing motion
selects 7 ", 10 ", 12" record size. Arm literally floats down to record on air. Absolutely no
connection between arm and table. $75.00 net.
Base $6.00.
TD -134. 4 -speed turntable with integral arm
for manual operation.
Same high- performance
tone arm as used on
.411110,
TD -184 equals tracking
performance of arms
costing as much as half
the price of this entire unit. Same adjustable
speed drive mechanism as on more expensive
units. $60.00 net. Base $6.00.
9.5
SWISS MADE PRODUCTS
MUSIC BOXES
HI -FI COMPONENTS
SPRING -POWERED SHAVERS
LIGHTERS
Write Dept. .4-3 for catalog
on complete Thorens hi-,fi line.
AUDIO
NEW HYDE PARK, NEW YORK
MARCH, 1959
17
www.americanradiohistory.com
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EDITOR'S REVIEW
RED FACE
DEPARTMENT
but we sometimes wonder why we keep trying to prove the truth of this
old saying. In particular, we are referring to a
New Products item at the bottom of page 76 in the
February issue which commenced, "Hardly any desirable audio control function is incorporated in the
Pilot Model 216 stereophonic preamplifier...."
Now we don't think any of AUDIO'S readers would
take this at its face value-anyone ought to know that
if we thought the product had no desirable features we
would simply ignore the publicity release and leave
everything unsaid. However, two people were mislead
and mentioned it to us, so we could rectify the error.
Actually, the original release was correct ; our New
Products editor wrote it correctly ; the printer set
the type correctly ; and finally, one of our own proofreaders spied the "not," thought it was in the wrong
place, and marked it to be deleted. The obliging
printer, not being expected to edit the magazine too,
removed the "not," which was not right. So now we
have to write about the not that was not written in the
mgaazine, and we hope it will not happen again. Not
that we expect it not to.
Anyhow, Pilot gets another mention of the SP -216which is a slightly improved model of the SP -215 about
which we have commented favorably many times.
While we are in an apologetic mood, we offer the
following corrections to the November article by Philip
B. Williams and James F. Novak, "Improvements in
`air suspension' speaker enclosures with tube venting." Equation (8) should have had a radical sign
over the first 2 in the denominator ; in Fig. 2, MmR
should have been shown as equal to "Total air load
mass, kilograms," instead of "Total IR load ... "; the
abcissa of Fig. 7 should have read "Frequency in
cycles per second" instead of w /w8j and the abcissa of
Fig. 8 should have been w/we instead of w /wo. The Fig.
2 error was our fault; and the authors are kind enough
to say that the other mistakes were theirs.
No matter how hard we try, these errors will etc.
ARDLY ANYONE IS PERFECT,
etc. etc. etc.
STEREO RECORD QUALITY
We still hear comments from some readers-with,
possibly, short memories-relative to the alleged poor
quality of stereo records. To be sure, we have heard
some poor stereo records, but we have also heard some
superb ones. Furthermore, we have seen consistent improvement in record quality since the first ones were
introduced over a year ago. By and large, we believe
AUDIO
the record industry has taken a new tool and within
the short space of a year has learned new techniques
of record cutting and processing, to say nothing of
microphone techniques, which are not yet standardized
but which are being employed rather dramatically in
many instances to produce excellent records.
When we consider how many times we have heard
poor stereo reproduction-and so often due only to
an out -of -phase condition of the speakers -we can
understand why the records are often blamed. But
when the system itself is right -and that proves itself
if at least some records sound good -there are many,
many good stereo records. Our own collection is not
large, compared to the monophonic collections of the
average music lover, but at last count it numbered
about 65 records. And of those 65 we would say that
at least half are excellent, and only a dozen poor.
One would not think of evaluating monophonic LP
record quality by playing the discs on a table model
phonograph of the $29.95 "hi fi" variety. And it is
just as important that the system be of top quality for
stereo
not more so-than for monophonic reproduction. Remember, furthermore, that some of the
first LP's were far from perfect.
Occasionally we receive an irate letter from a reader
who says he would never buy a stereo record because
"they are no good" or that "they have a false stereo
perspective," or for some other reason. We do believe
that there is a variation in recording and microphoning techniques, but we also believe that it is necessary
to take a little more care in setting up a stereo system
-both electrically and acoustically, with the accent on
the latter -than it is for a good monophonic system.
Perhaps we have been lucky in either records or equipment, or both, or perhaps we have expended more effort in getting what we consider satisfactory reproduction. But the result is that we think many stereo records are excellent, we have dropped our membership
in the Metropolitan Opera Record Club until they are
in stereo, and we will not buy any more monophonic
records unless some performer we want is not yet recorded stereophonically.
But that is only our opinion.
-if
WEST COAST SHOWS
Unfortunately, the San Francisco and Los Angeles
shows were too late for any report in this issue. The
Cow Palace show in San Francisco differed from the
typical room shows held heretofore, and readers will
undoubtedly be interested in how the new type of show
building went over. We would too, but we will also
have to wait a while longer.
MARCH, 1959
19
www.americanradiohistory.com
THEY PROBE THE
FUTURE OF DEEP -SEA TELEPHONY
Deep in the ocean, a submarine telephone cable
system is extremely hard to get at for adjustment or
repair. This makes it vitally important to find out what
can happen to such a system be /ore it is installed.
Bell Laboratories engineers do this by means of
tests which simulate ocean floor conditions on dry land.
Among many factors they test for are the effects of
immense pressures on amplifier housings and their
water -resistant seals. They also test for agents which
work very slowly, yet can cause serious destruction over
the years- chemical action, marine borers and several
species of bacteria which strangely thrive under great
pressures.
Through this and other work, Bell Telephone
Laboratories engineers are learning how to create
better deep -sea telephone systems to connect America
to the rest of the world.
Highly precise instruments developed by Bell Laboratories engineers are used to detect infinitesimal changes in cable loss
to an accuracy of ten millionths of a decibel.
-
"Dry Land Ocean," under construction
at Bell Laboratories,
simulates ocean floor conditions, is used to test changes in
cable loss. Sample cables are housed in pipes which contain
salt water under deep -sea pressure. The completed trough is
roofed in and is filled with water which maintains the pipes
at 37° F., the temperature of the ocean floor.
BELL TELEPHONE LABORATORIES
WORLD CENTER OF COMMUNICATIONS
RESEARCH AND DEVELOPMENT
Seawater and sediment in bottle characterize ocean floor. Test
sample of insulation on coiled wire is checked for bacterial
attack by conductance and capacitance tests.
www.americanradiohistory.com
Loading the
Piezoelectric Cartridge
HERMAN BURSTEIN
Optimum performance from ceramic or crystal phono pickups may be obtained when they
are matched to the amplifier input correctly. Here are the reasons, and some of the cures.
THE
I: EZOEL.ECTR IC phono cartridge,
once disdained for high fidelity service, has become a full -fledged member
of the high fidelity fmily, particularly
in view of the facility with which it
lends itself to stereo design. However,
its suitability very much depends upon
its being properly loaded. Essentially,
the loading problem is one of maintaining proper equalization of the RIAA recording characteristic; at the same time,
output level and distortion are also at
stake.
Voltage output of a piezoelectric
cartridge (usually ceramic, though sometimes crystal) is proportional to recorded amplitude, rather than to velocity as in the case of a magnetic
pickup. Hence the equalization requirements differ radically from those for a.
magnetic cartridge. Whereas the magnetic requires bass boost and treble eut,
the piezoelectric needs bass cut and
treble boost in order to match the RIAA
recording curve. See Fig. 1.
To obtain bass eut that reasonably
compliments the RIAA recorded amplitude characteristic, the total circuit
capacitance- enrt.ridge, cable, and input
tube-and the load resistance should
have a time constant of about 1000 to
1300 microseconds. For example, assume that a piezoelectric cartridge has
$80 Twin Lane E., lt'antagh, N. Y.
500 µµf capacitance, which is typical,
and works into a typical load of 500
ohms. But in order for RC to be, say,
1300 Microseconds, total circuit capacitance should he 2600
instead of
500 µµf. Allowing 500 µµf for the
cartridge and about 200 ituf more for
the cable and input -tube capaeita ce.
another 1900 µµf is required across the
cartridge in order to achieve the correct
amount of bass cut; that is, to avoid too
much bass cut. The equivalent circuit
is shown in Fig. 2. This of course is a
high -pass filter, producing a decline in
response below the frequency at which
total capacitive reactance equals load
resistance.
Instead of adding a shunt capacitor
across the cartridge, the required time
constant could be obtained by adding a
1.4- megohnn resistor in series, as shown
in Fig. 3. However, the disadvantage of
this method is that the input capacitance
of the input tube and the parallel resistance of the 1.4- megohni and 500 -K
resistors form a low -pass filter, causing
a loss in response at high frequencies.
The equivalent circuit at high frequencies appears in Fig. 4. Assuming an input capacitance of 50 µµf for the input
tube, a reasonable figure for a triode
such as the 12AX7, response would he
3 db down at about 8600 cps, declining
thereafter at a rate approaching 6 dh
SHUNT CAPACITANCE
(CABLE, TUBE, ETC.)
ADDITIONAL LOAD
CAPACITANCE
if
per octave.
Fig.
1.
RIAA am-
OUTPUT
CL
2
Ca
300 Pyf
PPE
RL
1900
LOAD
PP'
RESISTANCE
(A)
OUTPUT
C,
Time Constant
1
RL
300 psec.
(B)
Fig. 2. (A), Loading for a piezoelectric
cartridge to produce RIAA equalization
and (B), its equivalent circuit.
Methods of Correcting
Thus it is preferable to obtain the
required time constant by means of a
shunt capacitor. Both methods will result in signal attenuation because either
a capacitive or resistive voltage divider
is formed so far as signal output is concerned. Figure 3 already shows how a
resistive voltage divider is formed, while
Fig. 5 shows how a capacitive voltage
divider results from the preferred
method.
The loss in output voltage is in many
eases a good thing, insuring that the
signal is sufficiently low to prevent overloading the input tube. The writer has
come across situations where cartridge
signal was so great relative to the sensitivity of the control amplifier that the
gain control could barely be turned up
(Continued on page 74)
plitude playback
equalization.
R
Cc
300 PPf
Cs
200PPf
OUTPUT
1.4 MaB.
RL
tima Constont
1330 ,Rec
Alternative means of loading a
piezoelectric cartridge to produce RIAA
Fig. 3.
Ia
NX910M
FREQUENCY IN CYCLES PER SECOND
AUDIO
equalization.
MARCH, 1959
21
www.americanradiohistory.com
Design of the Wide -Range UltraCompact Regal Speaker System
ROBERT C. AVEDON,
WAYNE KOOY, and
JACK E. BURCHFIELD
Since small loudspeakers have become particularly popular for stereo installations, it is only
natural that different concepts of design would be reached by different manufacturers; all,
however, directed toward achieving a high degree of performance in a minimum of volume.
IN RECENT MONTHS the ultra- compact
loudspeaker system has become popular where space limitations must be
met. Most people are reluctant to sacrifice sound quality for extreme compactness. The ultra -compact loudspeaker
must preserve much of the sound quality
available in present day larger systems
in order to be acceptable for high fidelity
use. Unfortunately, many misconceptions exist concerning this type of
speaker and include matters of efficiency,
size, distortion, and a variety of constructional details.
The ultra -compact cabinet has one big
advantage: small size. However, no
diminutive speaker system can perform
because of its size. On almost every point
of performance the small cabinet
speaker is at a disadvantage. These performance problems must be solved on a
compromise basis.
It is the purpose of this article to
dispel the present misconceptions and
to arrive at the optimum design requirements for the ultra- compact loudspeaker.
The reader is invited to follow a series
of experiments and to participate in the
Engineers, Electro- Voice,
chanan, Michigan.
Inc.,
Bu-
arrival at the optimum solutions that
are found in the Electro -Voice Regal.
Bass Response and Efficiency
The well known problem encountered
in preserving high fidelity sound quality
in a very compact enclosure is achieving
a flat bass range with reasonable efficiency. The objective treatment below
will illustrate the bass -range problem.
A cabinet which was built for the experiments enclosed 2500 cubic inches or
about 1.4 cubic feet, excluding the volume taken up by drivers and crossover
networks. This volume is the generally
accepted size for bookshelf type speakers.
All frequency- response curves were
machine run with the speaker placed in
a free field corner. The free field corner
consisted of 8 foot high false walls built
on a flat roof. These walls extended 10
feet in either direction from the corner.
A conventional dynamic 12 -inch cone
driver of high quality having a free air
resonance of 39 cps was "infinitely"
baffled in the 1.4 cubic foot cabinet. (A
free air resonance of 35 to 45 cps is
representative of a 12 -inch driver of this
type.) The primary or first resonance of
The
Electro -Voice
Regal Ill
the system occurred at 88 cps. When
swept with an oscillator at constant
voltage the acoustic output began to fall
with decreasing frequency below 88 cps,
becoming at 40 cps about 12 db down
from the nominal output above 88 cps.
Obviously, a system which reaches to
only 88 cps before its output begins to
diminish cannot be acceptable for high
fidelity reproduction because of lack of
musical balance.
How, then, is the bass response to be
extended fiat below 88 cps in this experiment? The most obvious attack
(and, in fact, the very crux of the matter when dealing with sealed cabinet
systems) is simply to lower the first
resonance of the system. Unfortunately,
simply lowering the system's first resonance is a matter requiring consideration of sacrifice in efficiency and transient response. A digression dealing with
equivalent electrical circuits will show
why efficiency and transient response
must be sacrificed to accomplish lower
bass range.
Equivalent Circuits and the Bass Range
The electrical circuit analogies pertaining to the driver in free air and to
the sealed cabinet system will now be
examined.
The free -air resonance of a cone
driver is determined by the mass of the
entire moving assembly and its mechanical suspension compliance. The equivalent circuit of a cone unit, operating in
free air, is shown at (A) in Fig. 1. Mc
represents the moving mechanical mass,
Al, represents the air mass load, and Cs
is the combined compliance of the suspension (spider and rim rolls). R,. represents the radiation resistance component of the air load as seen in the
mechanical circuit, and R,,, represents
any mechanical resistances in the moving
assembly. This circuit shows an impedance at resonance of just the radiation resistance plus the mechanical re-
AUDIO
22
www.americanradiohistory.com
MARCH, 1959
sistance. At this frequency the cone velocity will be maximum, limited only
by this radiation and mechanical resistance.
When the driver unit is baffled in a
small sealed volume the mechanical system has the equivalent circuit shown at
(B) in Fig. 1. Because the rear of the
driver piston is now enclosed, front to
back cancellation is eliminated, and the
radiation resistance,
is increased and
appears wholly on the front of the cone.
The radiation to the rear into a small
cavity at frequencies in the bass range
is essentially non-existent. Rm, the mechanical resistance of the moving assembly, remains the same. Ma, the air mass
load, is increased by virtue of the presence of the baffle. But the most significant change as far as this discussion is
concerned is the addition of another
series compliance component, Ca. This
addition is due to the sealed cavity behind the cone. Recall that the primary
resonance was higher for the driver in
the sealed cabinet than for free air operation. This is caused by the addition
in series of the air cavity compliance,
Ca, which affected a reduction in the
total compliance seen by the driver.
R
M,
Ma
III
C,
III
Rm
e
(A)
M
III
C,
M,,
III
Rm
r
A
ca
(e)
M,
M,
I
A
M1
C,
R,,
I
R
ci
(C)
Me
C,
R5,
R,
Co
MI
F
--AIR
--
LEGEND
MOVING MECHANICAL MASS
LOAD MASS
SUSPENSION COMPLIANCE
-MECHANICAL
RESISTANCE
RADIATION RESISTANCE
SEALED CAVITY COMPLIANCE
-MASS
ADDED TO
MOVING ASSEMBLY
DRIVING FORCE OF VOICE COIL
Fig. 1. Equivalent circuits: (A) Conven
tional cone driver in free air, and (B)
"infinitely" baffled in small sealed cab
inet; (C) Weighted cone driver "in
finitely" baffled in small sealed cabinet
AUDIO
d
5
NO ADDED MASS
34 GRAMS ADDED MASS
R
Lowering the Resonance
S
IF
Me
Returning to the experimental system
it will be seen that for a constant applied voltage on the driver voice coil the
system will exhibit a flat energy output
from resonance (88 cps) to approximately 1000 cps. Although the mechanical velocity of the piston is falling 'with
increasing frequency above resonance at
approximately 6 db per octave, the radiation resistance component,
of the
air load is rising 6 db per octave (taken
as a power ratio). The radiation resistance is a function of frequency up
to about 900 or 1000 cps for a nominal
12 -inch cone, quadrupling each time the
frequency is doubled. At this frequency
it reaches an ultimate value and is eonstant for all higher frequencies provided the cone still operates as a rigid
piston. But all 12 -inch cones break up at
approximately 1000 cps. Therefore, the
considerations at present must be limited
to frequencies below 1000 cps for the
single degree of freedom circuits of
Fig. 1 to be valid.
The falling cone velocity just complements the rising radiation resistance for
frequencies between resonance and 1000
cps. Such a fortuitous combination of
circumstances leads to flat acoustic
energy output in this range. Below resonance, however, the cone velocity drops
nearly 6 db per octave with decreasing
frequency while the radiation resistance
also drops 6 db per octave with decreasing frequency. Thus, in the frequency range below resonance a complementary situation between the radiation resistance and the cone velocity does
not exist and the result is falling response below resonance at the rate of
about 12 db per octave. The exact roll off characteristic below resonance depends on the cone size and, hence, the
relative value of the circuit parameters.
Now that it is clear exactly what problems exist and why the system's first
resonance must be lowered, a discussion
of resonance- lowering techniques can
proceed.
It is contended by some manufacturers of ultra -compact speaker systems
that when the conventional driver is
baffled into a small sealed volume the
total stiffness as seen by the driver piston is increased, resulting in greatly
raised primary resonance for the system with bass response lacking below
this resonance.
The previous discussion has shown
this to be quite true. This school further
contends: To lower the resonance and
obtain a flat bass response the total stiffness can he reduced sufficiently by virtual elimination of the mechanical stiffness of the driver suspension, leaving
the sealed cavity as the only stiffness. It
is claimed also that elimination of the
MARCH, 1959
o
IMO
FREQUENCY
Fig.
CYCLES PER SECOND
of added mass on cone
baffled in small
2. Effect
driver
IN
"infinitely"
sealed cabinet.
mechanical suspension provides extreme
linearity of cone movement due to the
linear air spring of the enclosed cabinet
volume as compared with the extremely
non -linear mechanical cone suspension.
Are these presumptions correct? Further experiment will reveal that this is
not correct.
Attention will now return to the experimental cabinet and the 12 -inch
driver used with it. A series of experiments were performed to determine how
much the resonance could be lowered by
completely removing the driver's mechanical suspension. The description of
these experiments to follow will show
how moving -mass, mechanical- compliance, and air-cavity -compliance data
were collected and used to find the new
resonance without a mechanical suspension.
The moving mass was found by the
following method. Recall that the free
air resonance of the driver was 39 cps.
A metal ring serving as an added mass
and weighing 28.2 grams was cemented
firmly to the cone at its apex. The free
air resonance was now observed to be
28.5 cps.
The equation shown describes resonance under these circumstances:
1
l-2'VMC
(1)
where f is the resonant frequency, M is
all the moving mass involved, and C is
the total compliance.
The new free air resonance obtained
with the added mass in conjunction with
the former free air resonance applied to
Eq. (1) will allow computation of the
mechanical suspension compliance and
the total moving mass of the driver and
air load.
Two independent equations will be
necessary and are derived from Eq. (1).
1
f'
2nN/MC
(2)
(3)
fR =2a J(M +28.2)C
where f, is the resonant frequency without added mass and fr is the resonant
23
www.americanradiohistory.com
found. From the equivalent circuit of
(13) in Fig. 1 recall that the suspension
compliance adds in series with the cabinet- air -volume compliance. The total
compliance of two series compliances is
not their arithmetic sum. But the total
stiffness (reciprocal of compliance, 1 /C)
is the arithmetic sum of two series stiff uesses. Then it can he said :
frequency with the added mass of 28.2
grams.
Simultaneous solution of Eq's. (2) and
(3) for M obtains the expression
(4)
M. (28.2) /EZt
fs_
,
Pf
Substitution of the resonant frequencies yields for the total moving
mass including air load : M = 32.3 grams.
It is noteworthy that the moving mechanical mass of the driver determined
by weighing the moving assembly on an
analytical balance is just 15.0 grams.
One concludes, then, that the air-load
mass for free-air operation must be 17.3
grams. Rearranging Eq. (2) and substituting for the total moving mass a
value of 32.3 grams along with the unweighted free -air resonant frequency of
39 cps, the mechanical compliance is
found to be:
1
Ct(TOTAL)
1
CA
(6)
Now knowing the values of the suspen-
sion compliance, Cx, and of the total
compliance, Ct, the compliance of the
air volume is found to be 0.119 (10) -6
cm/dyne by Eq. (6).
The reader can see that the total of
two series compliances is always less
than the smallest of either of the two
compliances individually.
At this point a simple computation
will be made to find the new resonant
frequency obtainable, conceding that
the mechanical compliance could be completely removed.
Return to Eq. (1) and calculate the
resonant frequency of the driver with
its unaltered mass of 33.7 grams sealed
into the example cabinet volume of compliance 0.119. Notice that the mechanical
compliance of the suspension has not
been included.
Frighteningly enough, by completely
eliminating the suspension compliance
the resonance drops to 79.5 cps, a mere
8.5 cps decrease from the situation including the suspension compliance! Is
this the improved result desired'? Such a
reduction in resonant frequency of only
a little over 10 per cent is a piddling
effort at best!
It is quite obvious that mere elimination of the suspension compliance is not
enough to effect a large reduction in
resonant frequency. Re-examination of
the equivalent circuit of (B) in Fig. 1
and Eq. (1) will reveal the only other
cm.
- 0.514(10 ")
1
Cx
(5)
C= .2,:11
This means that the application of one
dyne of force will move the cone about
one-half millionth of a centimeter.
At this juncture there has been determined the total moving mass and the
suspension compliance for the free -air
case. The total moving mass and the
total compliance (suspension plus air
cavity) has also been determined at this
time by the same method for the same
driver sealed into the experimental cabinet. Recall that the primary resonance
was 88 cps for this case (no added
mass). With the same added Mass of
28.2 grants the resonance dropped to
65 cps. By the same method of solution
as for the free -air case the total moving
mass was found to be 33.7 grams (an
increase of 1.4 grams over the free -air
case) and the total compliance was 0.097
(10) -6 cm /dyne.
The compliance actually contributed
by the cabinet air volume will now be
17_
alternative to reducing the resonant frequency. Further lowering of resonance
can be accomplished only by addition of
mass. Here is where the supreme sacrifice in efficiency conies. Referring to (C)
in Fig. 1 a mass is added in series in
the form of additional weight of cone
material (thicker cone) or say, a machined metal ring affixed to the voice coil
forms. It is seen plainly that this additional reactive element will reduce the
velocity circulating through the radiation resistance, R,., above resonance
with consequent reduction in acoustic
output for the saute driving force. The
driving force is produced by electrical
current circulating through a voice -coil
wire containing electrical resistance.
Thus, with the same driving force the
electrical losses remain the same but
the acoustic output drops as mass is
added to the moving system. Consequently, the over-all efficiency of the
system drops.
It is worth noting that each time the
moving mass is doubled the acoustic output above resonance drops 6 db for the
salue voice -coil current. If this is true,
then the addition of exactly 33.7 grams
to the moving assembly of the driver (in
its original form "infinitely" baffled in
the experimental cabinet) should reduce
its output just 6 db. Recall that the
total moving mass was previously determined to be 33.7 grams. The addition
of a like mass of 33.7 grants reduced the
output, on an average, about 6 db for
frequencies above 100 cps in this case.
The curves shown in Fig. 2 are reproduced from machine -run charts.
So it is seen that the decision the design engineer must make in the ultra compact cabinet is to make an optimum
compromise between loss of efficiency
and lowered resonance. A resonance of
55 to 60 cps with an efficiency loss of
7 or 8 db would be an excellent optimum
compromise and is the situation existing
COMPLIANCE ROLLS
RING WEIGHT
DUST DOME
M
i
I
SPIDER
PiltiiMM
Y
CE
COIL FORM
LOCIA
ED_
ON CONE
r
/,1;:_
2
WEIGHT LOCATED ON VOICE COIL FORM
VOICE COIL WIRE
I
I
I
I
FREQUENCY
IN
I
im
t¡
I
I
l
lomo
1000
CYCLES PER SECOND
(0)
(A)
Fig. 3. Adding moss to cone
driver moving assembly. (A) Cross section of driver showing ring weight added to cone.
on frequency response of added weight location.
AUDIO
24
www.americanradiohistory.com
(B) Effects
MARCH, 1959
z
>o
loo
FREQUENCY
Fig.
IN
CYCLES PER SECOND
of cabinet leaks on fre
quency response.
4. Effects
in the Regal system. Because the resonance in this system shows up as a very
broad effect in the acoustic output the
level at 35 cps is down from the resonance level only 5 db measured in the
free field corner.
How can the additional mass required
to lower the resonance be added to the
moving system? The problem in adding
mass to the moving system is maintenance of a smooth frequency response
which is uniform from speaker to
speaker. A cone which is constructed so
that it is heavier than a conventional
cone can be used. Molded paper cones
are made by placing forms in a slurry.
It is difficult to maintain a uniform
thickness when forming a heavy section
by this method. A more precise way to
add extra mass is just the way it was
done in the experimental ease discussed
-in the form of a machined metal ring
affixed to the cone and concentric with
the voice coil. However, a problem arises
in the placement of this extra mass.
Locating the Mass
In Fig. 3, (A) shows a ring of arbitrary diameter on the cone, and (B)
shows the response of this driver in the
experimental cabinet. Point 1 on the
curve is the primary or first resonance.
Point 2 is the frequency at which the
ring weight goes into resonance with
the effective compliance of the cone surrounding it. At this frequency, the voice
coil sees an anti- resonant condition and
a dip is produced in the response. Point
3 on the curve is the frequency at which
the cone has "broken up" and the ring
is nearly standing still while the voice
coil and central cone area are in vigorous
motion. This frequency is a new resonance for the moving system as seen
from the voice coil. Here the effective
compliance of the cone from ring to
voice coil along with the spider compliance is in resonance with the distributed mass of the cone from ring to voice
coil, the air mass load on this part of
the cone, and the voice coil mass. As the
ring is made of smaller diameter (but
the mass held constant) and as it comes
closer to the voice coil, points 2 and 3
move higher in frequency. When the
AUDIO
ring is mounted directly to the voice
coil form the system returns to a single
degree of freedom and Points 2 and 3
on the curve disappear. Under this condition the system returns to its original
operation up to 1000 cps with the exception that the level is lower due to the
added mass.
Note the higher output above Point 3
in (B) of Fig. 3 with the weight placed
somewhere out on the cone as compared
with the output for the same frequencies
with the weight attached to the voice coil form. With voice -coil form mounting the weight never "decouples" and
the system has always one degree of
freedom up to the frequency where the
cone would normally break up. With the
weight mounted somewhere on the cone
it goes through the process of decoupling between Points 2 and 3 in the
curve. Above Point 3 the system operates with reduced mass with the ring
and cone area outside the ring essentially
inoperative. Hence, the higher output.
Another important consideration is
that a cone has a lower effective mass
above 1000 cps because of breakup. All
of the cone does not move, and therefore
the effective mass is less. This causes the
difference in curve shape above 1000 cps
between the original driver and the unit
weighted at the voice coil form. When
the cone breaks up a higher ratio of
added mass to original moving mass
exists. As a result the output above the
breakup is reduced (by comparison to
the original driver) in greater proportion than is the output below breakup.
If the breakup frequency is adjusted by
choice of cone geometry to coincide with
the frequency of crossover into the next
driver this phenomena can be put to
good use by letting it aid the electrical
networks in attenuating the output of
the low -frequency driver above crossover.
Non -linearity and the Sealed Back Cavity
It has been contended that the mechanical suspension non -linearity is
much greater than the extreme linearity
of the air spring or sealed air volume of
the cabinet. This is not true. In any good
Rear
view,
physics text one can find proof that
sound is an adiabatic process. This
means that when air is compressed or
rarefied in the sealed air cavity behind
the speaker there is no heat transfer to
or away from the cabinet walls or interior components.
It is extremely difficult to make this
process anything other than adiabatic.
The physics text will also show that
adiabatic compression is inherently nonlinear. However, for small pressure variations relative to the ambient atmospheric pressure the non -linearity is
vanishingly small. Consider a conventional 12 -inch speaker in a 6 -cubic -foot
box. When undergoing the excursions required for satisfactory bass response
the pressure variation relative to ambient atmospheric pressure is indeed small.
However, when a 12 -inch piston in an
extremely small box undergoes these
necessary excursions there are much
larger pressure variations relative to
ambient atmospheric pressure. These
larger pressure variations must cause
greater distortion for a given excursion
of the cone due to the inherent non linearity of the adiabatic process. This
is an unavoidable consequence of the
laws of physics. So when it is said air
suspensions are inherently more linear
than mechanical suspensions a misstatement has been made, for mechanical
suspensions are often made that are
snore linear than these compact air
springs.
Leaks in the Back Cavity
Need the cavity behind the driver be
sealed absolutely air tight, resorting
even to a stethoscope to detect minor air
leaks? Even at the lowest usable frequencies the inductance of a small leak
is high enough to prevent any loss in
output. A test to prove this has been
conducted in the following manner: A
frequency response curve was run on a
perfectly sealed cabinet containing a
12 -inch loudspeaker. A small hole of a
1/4-in. diameter was drilled into the
cabinet and another response curve was
run. This process was repeated many
times with more holes and more fre-
Elec-
tro -Voice Regal Ill
MARCH, 1959
25
www.americanradiohistory.com
coil outside the dense flux field do not
contribute to the driving force but do
add d.c. resistance, an undesirable con-
f
ß
5db
z
I
i
-
/r_
..»..
20
v
No Bock-Coviry Podding
_
Bock Cavity Filled With
Sound Absorbent Podding
.. lilt
1
I
WI
I
I
m
FREQUENCY IN CYCLES PER SECOND
I
00
Fig. 5. Effect of filling small sealed -back
cavity with sound absorbent material.
queney response curves. The results are
shown in Fig. 4.
It is seen that nowhere was the output reduced by more than 1 db with a
total of eight 3/4-in. holes. This represents a substantial air leak. Therefore,
a well crafted box with reasonable
joinery is all that is necessary.
While on the subject of cabinet construction it might be noted that for a
box of this size 3/4' lumber stock is entirely adequate. No panel vibration of
any consequence whatever will be experienced.
Use
of Absorbent Material in Small
Cabinets
At this point mention should be made
of filling the back cavity of ultra -compact cabinets with sound absorbent material. A test was conducted in the following manner: Curves were run on a
sealed box system in the free field corner
with and without the interior of the box
filled with sound absorbent material.
The two curves are shown in Fig. 5.
With accurate recording equipment the
results show a negligible difference between the two curves. Filling the interior
of small cavities with sound absorbent
material is unnecessary.
Long-Throw Voice Coils vs. Efficiency
The throw of the voice coil is defined
as the maximum excursion it can execute
without distortion due to non -linearity
of movement. At any particular frequency the excursion will be proportional to the voice -coil current as long
as the same number of turns of the voice
coil always remain in the dense flux
field. In Fig. 6, (A) shows the voice coil flux configuration for maximum efficiency. However, this arrangement will
not be able to move without causing distortion because any excursion will remove turns from the gap; (B) shows a
voice -coil arrangement where a constant
number of turns will be maintained in
the flux field with excursion. Twice the
amount of overhang, X, will be the total
excursion available without non -linearity.
Overhang results in a loss of efficiency,
and the greater the overhang the greater
the loss of efficiency. Turns of the voice
dition.
A compromise must be struck between
linearity and efficiency. The maximum
total excursion is dictated by the lowest
usable frequency and the maximum
practical listening level. The excursion
is limited by the maximum tolerable
distortion which is caused by the nonlinearity of the air spring. This non linearity is due to excessive pressure
variation in the back cavity. For a 12inch direct radiating speaker operating
at 35 cps, 3/8-in. total excursion will provide room shaking level. The low -frequency driver in the Regal system employs a voice coil with a 3 /16-in.
overhang. This provides 3/s -in. total
linear excursion. Any more linear excursion than this is unnecessary and
results only in further loss of efficiency.
The non -linearity of the air suspension
overshadows any reduction in distortion
derived from a throw longer than 3/4-in.
Transient Response and Series Resistors
To increase the bass level it is sometimes recommended that a resistor in
series with the system be used. This is
not good, for under these conditions the
benefits of the high damping factor in
a quality amplifier are destroyed. Without sufficient damping the low-frequency
driver at resonance is essentially "free
wheeling" (undamped), resulting in a
peaked output at primary resonance
along with greatly increased transient
distortion. In some ultra -compact systems the transient characteristics have
already been degraded by the excessive
addition of mass. Anything which further degrades the transient response is
retrogressive.
Additionally, series resistance results
in another loss of efficiency which cannot be afforded in the ultra-compact
loudspeaker.
ance the lower frequencies. If the horn
has a small lateral dimension compared
to the wavelength of the lowest frequency it is to reproduce, the dispersion
will be excellent. The flat response curves
frequently published do not tell the
complete story unless dispersion or polar
pattern is taken into account. It can be
seen that a flat curve on the axis with
progressive beaming at the higher frequencies would sound deficient in highs
unless the listener were directly in front
of the speaker. The dispersion of horns
of the diffraction type is the best by
far that is available and a smooth off axis frequency response is easily obtained. A superior advantage of horn
loading is that a small movement of the
diaphragm will provide high acoustic
output. This small movement allows
completely linear operation of the diaphragm. If care is taken in loading the
horn to the diaphragm, annoying dips
and peaks found undesirable in many
horn units are completely removed.
Some alternate efforts to achieve good
high-frequency performance are inadequate. Attempts to promote smooth dispersed high frequencies by using a small
dome radiating directly into the air have
been tried. While these domes give good
dispersion, they fail miserably in delivering efficiency, and low distortion.
To illustrate, a unit was made from a
2 -in. dome and a 1 -lb. Alnico V magnet.
The response was only fairly flat on axis
and the distortion content averaged 20
times higher for the same acoustic output than that derived from a comparable
horn- loaded unit. The efficiency was 15
db below the horn unit. This means that
for the same output the diaphragm was
moving ninny times further than in the
horn unit. This extreme excursion made
linear movement practically impossible
(Continued on page 68)
VOICE COIL FORM
DENSE
FLUX
LINES
The Mid and High Frequencies
The reader's attention is now directed
to the mid and high frequencies. The
following design features are considered
desirable, and are especially effective
for stereo reproduction : smooth response, good distribution, and low distortion of the mid -range and high frequencies. Excess efficiency in the treble
and high -frequency drivers along with
continuously variable controls allow the
listener to compensate for room conditions and his own individual taste. Many
compact systems provide a switched
variation of only t 2 db which is inadequate.
A horn- loaded radiator provides a
good match of the diaphragm to the air
load and more than enough level to bal-
VOICE
COIL W IRE
(A)
VOICE
COIL FORM
OVERHANG
(X)
VOICE
COIL
DENSE
WIRE
(B)
Fig. 6. Voice -coil geometry. (A) Voice coil
no longer than dense flux field. (B) Voice
coil overhanging the dense flux field.
AUDIO
26
www.americanradiohistory.com
FLUX
LINES
MARCH, 1959
The Decibel -Fact or Fable?
WALTER
R.
WESTPHAL
-
Although repeated many times in audio literature, the information about the decibel and its uses
and misuses -must be thoroughly understood by anyone who wishes to understand specifications.
has long been the subject
of a hazy issue in electronics. It is
used a dozen times in each issue of
electronics and high -fidelity magazines
and each time it seems to be used in a
different way. The reader imagines that
a wealth of higher mathematics is needed
to understand its use. And a lot of careless usage has made him wonder if anyone really understands the decibel either!
What does it mean to read that an
amplifier has a frequency response of
"5 cps to 160 kc, within 1 db" or that
an oscilloscope response is "down only
3 db at 200 kc "? A microphone is said
to have an "output of - 60 db." An amplifier has a "hum level - 90 db below
20 watts." What do these statements
mean? Are these different uses of the
decibel or is there some common denominator present in all of these statements?
The decibel is an important concept in
the analysis of electronic equipment and
one which should not be left to the imTHE DECIBEL
agination.
In every case the decibel is a ratio of
two electrical powers. This ratio, like
any other ratio, is really a fraction having a numerator and a denominator. The
two values of power then become the
numerator and denominator of this fraction. One of these values is known as the
reference power and in any situation is
either expressly stated or what is more
common, is understood. In many cases
the difficulty is in knowing what value of
power is being used as the reference.
Definition
We now turn to a modern definition
of the decibel and see how it is used in
some examples.
Two power levels, P, and P11 are said
188 Jaekson Ave., North Tonawanda,
N. Y.
AUDIO AMPLIFIER
2
8V
V RMS
RMS
Fig. 1. The gain of an amplifier can be
expressed in decibels if input and output
power are known. The value of input
resistance
AUDIO
is
usually supplied by the
manufacturer.
to differ by n decibels when the following equation holds :
n =10 log P, /P2
where n is the number of decibels
P, is the larger of the two
powers
P, is the smaller of the two
powers
Both P, and P2 must be measured in the
same units (watts, milliwatts, etc.). The
ratio P, /P2 is always arranged so that
its value is greater than 1. To signify a
power gain we prefix a + sign and a
power loss is expressed by prefixing a
- sign. Contrary to some textbooks it is
not necessary to remember two separate
formulas and a little checking with numerical values will show this. It is only
necessary to add the + or - sign depending upon whether a gain or loss is encountered and this can always be determined by inspection.
We can now put this equation to work
by using it in a simple example. Figure
1. illustrates an audio power amplifier
whose power gain is to be measured. The
output power is seen to he
Pout = E2 /R = 82/16 = 4 watts.
The input power can be found in a
similar fashion once the input impedance
(assumed to be a pure resistance) is
known. The manufacturer usually supplies this data and in this case it is 1
megohm. Therefore,
Pin= E2/R = 22/ 1,000,000 =
0.000004 watts
The power gain is then
n = 10 log (4/0.000004)
n=60 db
A power gain is indicated here by output being greater than input. The fact
that this amplifier has a gain of 60 db
is of limited value in comparing it with
another amplifier or against certain
arbitrary standards. What is of greater
importance is the relationship between
the power output at some reference frequency (usually 1000 cps) and at many
other frequencies above and below this.
Let's illustrate this with another example
using the same amplifier as shown in
Fig. 1.
Suppose that the input signal remains
constant at 2 volts but that the power
output drops to only 1 watt at 50 cps.
Using the 4 watts (at 1000 cps) of our
original example as the reference, n
MARCH, 1959
would indicate a power loss of approxi-
mately 6 db.'
Presenting the Information
1f we could calculate the power output
at many different frequencies and plot
these data on semi -logarithmic graph
paper our results would look like Fig. 2.
Here zero db represents the power output at some reference frequency (here
1000 cps). Any output lower than this
would represent a power loss (- db) and
these values could be plotted versus frequency. Figure 2 is known as a universal
response curve and shows us something
about the response of an amplifier without regard to the actual power output.
This is convenient when comparing
several amplifiers as to frequency response alone. In fact, absolute values of
power are of small importance in studying response curves.
The reader has probably noticed that
in the above calculations power was
found by using E2 /R. And when two
values of power were being compared
(to find their ratio), one value of E2 /R
was divided by another value of E2 /R.
With the two values of R being the same
in both cases (16 ohms) we could have
saved some effort by simply dividing
E¡/E22 to obtain the power ratio. This
can be carried one step further because
10 log (E,2/E2') =20 log (E,/E,)
There are two very important points to
notice in regard to this formula. First, it
is simply a short -cut to finding power
gain; the result is not "voltage gain."
Secondly, the value of resistance across
which the two voltages are measured
must be equal. The neglect of these two
restrictions has led to much of the confusion regarding decibels.
(Continued on page 77)
1n =10 log 4/1=- 6.02db ( -sign indicates a power loss).
o
4 -2
Z -4
Z
á -6
u
30
100
1000
10 KC
100 KC
FREQUENCY
Fig. 2. A universal response curve. See
text for
details of how the curve
determined.
is
27
www.americanradiohistory.com
Acoustic -Front Damping in
Dynamic Microphones
W. T. FIALA
To provide smooth, flat response, all microphones require some form of acoustic damping on the
diaphragm. The author describes a new method which is claimed to give superior performance.
ACOUSTIC -FRONT
DAMPING is a
oPR'
arrangement of the controlling
acoustic resistance in dynamic
microphones which is distinctly different
from that found in conventional microphones. This article will describe the
mechanics and advantages of this new
design. It should be observed that the
moving -coil microphones, as developed
years ago', already include the intricate
details of design that are found with
scarcely a change in the microphones of
that generic type in widespread use today. The intricacy of the design is
illustrated by the fact that about twelve
acoustical or mechanical elements require correct proportioning in relation
to each other to produce the excellent
frequency response available with n
correctly designed instrument of this
type.
There have been changes in relatively
superficial details. For example, the
Altec 21B Condenser Microphone and
M -11 Microphone System set a new
pattern for small physical size that
brought the performer back into view,
and several moving -coil microphones
have since appeared with external dimensions made narrower and longer
with the object of obtaining some
measure of the same benefits. The interplay of the acoustical and mechanical
elements in a dynamic microphone at
high frequencies is rather complex to
the average non-specialist, so a general
Altec Lansing Corporation, 1.515 S.
Manchester Ave., Anaheim, Calif.
Thuras, Bell
1 E. C. Wente and A. L.
System Technical Journal, October, 1931,
pp. 565 -577.
description of the deer -all action is
given in rather easy stages. Although
this description alight be found quite
elementary, it may still prove useful as
a brief refresher.
In microphones of the moving -coil
and the ribbon types, energy is converted
from the acoustical to the mechanical
form by forces of the sound field acting
on a movable mechanical system, and
from the mechanical to the electrical
form by the movement in a magnetic
field of an electrical conductor forming
a part of the mechanical system. The
voltage induced in the conductor is proportional to its velocity.
The ribbon microphone derives its
name from the fact that the moving
conductor is in the form of a ribbon, a
fraction of one -thousandth of an inch in
thickness, positioned in a uniform magnetic field: The ribbon is free to move
under the forces of the sound pressure
in the case of the ribbon pressure -type
microphone, or the sound -pressure difference between two sides of the microphone in the case of the ribbon -velocity
type. Acoustical forces net directly on
the ribbon which comprises the entire
mechanical system. In the moving -coil
microphone the conductor is in the
form of a coil (of round wire or edgewise-wound ribbon) attached rigidly to
a diaphragm and positioned in an annular gap to move in a radial magnetic
field. The forces of the sound field act on
the diaphragm.
In both types of transducer, the conductor or the conductor -diaphragm assembly forms a simple mechanical system. When driven by a force the move-
of typical moving-coil microphone, and
equivalent circuit.
Fig. 1. (A) Schematic cross section
(B), its
Fig. 2. Velocity amplitude vs. frequency
for typical mechanical structure to show
resonance.
ment of the system is controlled by its
mass, its stiffness, and the power it dissipates in the mechanical or acoustical
resistance associated with it. Depending
on which of the three factors is predominant in controlling the movement,
the system is commonly described as
mass- controlled, stiffness -controlled, or
resistance -controlled. For either type of
moving -conductor microphone a flat
frequency response requires resistance
control. The driving force may he proportional either to sound pressure or to
sound -pressure difference, but we will
restrict the discussion to follow to microphones in which the driving force is
proportional to sound pressure.
Figure 1 shows, at (A), the schematic
cross -section of a mechanical system
typical for the moving-coil microphone.
The diaphragm is given a dome- shaped
center portion to provide maximum piston rigidity with minimum mass, and a
compliant edge zone formed in corrugations. The voice coil is cemented to the
base of the doused center portion and the
total oscillating mass M is the sum of
diaphragm and voice -coil class. The
compliance C is that of the edge zone.
it represents the losses of the system. If
the system is driven by a force F, the
velocity l' follows the same law as the
current 1 in the familiar electrical L -C -R
series resonant circuit, driven from a
constant -voltage source E as indicated
at (B) in Fig. 1. The so-called impedance analogy is used throughout this
AUDIO
28
www.americanradiohistory.com
MARCH, 1959
basic contributions to our culture
indebted to William Henry Fox Talbot for the invention of the photographic negative and
discovery of the laten: image. His work greatly advanced the art -science of photography. More than
a hundred years later the laboratories of James B. Lansing Sound, Inc., developed the principle
of radial refraction, a break -through which may prove to be equally s gn ficant
in the field of stereophonic music reproduction. First applied to the magnificent
JBL Ranger- Paragon, an instrument originally designed for use as a monitor
in perfecting stereo recording techniques, radial refraction has now been used in
We are
a
more compact, home -sized stereophonic loudspeaker system called the
refracting panel on the front of the dual
acoustical enclosure iltegrates two precision loudspeaker systems. A wide -angle
stereo field is radiated throughout the listening area. Radial refraction obviates the
hole in the middle, ping-pong effects, and split soloists which plague expedient
JBL Ranger -Metregon. The curved
stereo arrangements. No less than seven different speaker systems, including one with
new high frequency drivers, exponential horns, and dividing networks may be installed
in the Metregon. You may very well be able to use some of your present JBL loudspeakers. Write for
complete description of the JBL Ranger -Metregon and the name and address of the Authorized
JBL Signature Audio Specialist in your community.
a
JAMES B. LANSING SOUND, INC., 3249 Casitas Ave., Los
www.americanradiohistory.com
An`eles.39, Calif.
Fig. 3. (A), Schematic of moving-coil microphone with added acoustic damping, and
(B), its equivalent circuit.
article. Plotting the velocity amplitude
as a function of frequency gives the
well -known resonance curve depicted by
the solid line in Fig. 2. For frequencies
high compared with the resonant frequency, u),,, velocity is controlled by the
mass of the system; and for frequencies
low compared with too, by its stiffness.
The maximum velocity at resonance depends on the acoustical and mechanical
resistance of the system.
Air Damping Added
As a further step towards the more
complicated mechanical-acoustical structure of the moving coil microphone, (A)
of Fig. 3 shows the same basic mechanical system with added acoustical components. A case over the hack of the
diaphragm encloses a small air volume.
The case is provided with a hole (for
example, 1/8-in. diameter) which is covered or filled with felt, designated R, in
Fig. 3. If the diaphragm moves in the
direction of the force F, the enclosed air
will be partly compressed and partly
forced through the felt. The ratio of the
amount of compression to the amount of
air moved through the felt will depend
on the ratio of volume to the flow re-
sistanee of the felt. The compression of
the air will establish an additional stiffness for the mechanical system. The air
forced through the felt will dissipate
energy due to viscous friction and
thereby provide additional damping. In
the electrical analogue, (B) of Fig. 3,
the two acoustic components are represented by C, and R,. Provided the coupling volume is small enough that its compression can be neglected compared with
the amount of air moved through the resistance, only a series resistance R, has
to be added in the electrical equivalent
circuit. In this case the increased resistance decreases the velocity at resonance but provides a substantial range
where the velocity is independent of the
frequency of the driving force (dashed
curve, Fig. 2). In this frequency range
the movement of the system is resistance controlled. If R, is further increased, the
flat range can be widened at the cost of
further reduction of velocity. If the
voice coil of such a system moves in a
constant magnetic field which has a direction as indicated by the arrows in (A)
of Fig. 3, the voltage generated will be
proportional to its velocity and therefore independent of the frequency of the
PROTECTIVE SCREEN
C4
R4
M
I
POLE PLATE
M2 R2
CONTROLLING
RESISTANCE
POLE PIECE
MAGNET
MAGNET
STRUCTURE
CASE
(A)
ig.
4.
(A),
Schematic of
moving -coil
microphone showing additional acoustic
(B), its equivalent circuit.
compliances, masses, and resistances, and
driving force in the range where the
velocity is constant. This illustrates that
the movement of the mechanical system
of the moving-coil microphone has to he
resistance -controlled.
Figure 4 shows, at (A) a more complete schematic cross-section of a moving -coil microphone. Magnet, magnet
structure, pole plate and pole piece forni
the magnetic circuit, which provides a
radial magnetic field in the annular gap
between pole piece and pole plate. The
diaphragm voice -coil assembly is cemented to the pole plate so that the
voice -coil can move freely in the annular
gap perpendicular to the radial field. On
the other side of the gap, the controlling
acoustical resistance R2 with its mass
component M2, consisting usually of a
narrow annular slot or a felt or silk
ring, communicates the small volume Ce
with the volume inside the magnet structure. The whole system is enclosed by a
case which seals the back side of the
diaphragm from the sound field and
allows the sound pressure to act only on
the front side of the diaphragm, through
a protective screen. The volume of the
case C, must communicate freely with
the volume inside the magnet structure.
In the equivalent electrical circuit,
(B) of Fig. 4, if the components enclosed by the dashed lines are disregarded for the moment, M, is the mass
of diaphragm plus voice -coil, C, the
compliance of the edge zone, C2 is the
compliance of the small volume between
diaphragm and pole piece, which couples
the acoustical element RrM, to the diaphragm. C, is the compliance of the volume enclosed by the case. In the frequency range where Rs is large compared with the reactive components
M,C, and M,C and where the reactive
component of Cp is large compared with
Rp, the current through M,C which
represents the velocity of the diaphragm
will be resistance controlled and therefore independent of the frequency of the
driving sound pressure. It follows that
the output voltage of the microphone
will be constant in this frequency range.
At higher frequencies, diaphragm
mass M, resonates with the air volume
CE at, for example, 7000 cps. This resonance proves to be much less damped
than the natural resonance of the diaphragm and causes an undesired peak in
the frequency response of the output
voltage. The main reason why the damping resistance RR is less effective in this
frequency range is that the reactance of
its mass component M, becomes comparable with RE.
The equivalent circuit discussed so far
assumes that the sound pressure acts
directly on the diaphragm. It is necessary, however, not only to protect the
diaphragm aaginst mechanical damage,
but also to provide a fine enough screen
between diaphragm and sound field to
AUDIO
30
www.americanradiohistory.com
MARCH, 1959
Reduce record wear
Less mass, higher compliance with G.E.'s
"Golden Classic" stereo- magnetic cartridge
The more moving
-
parts, the more resistance to groove motion.
General Electric's "Golden Classic" has only one moving part
the stylus
which "floats" freely in special -formula damping
cushions. This meons freer motion in the record groove. You get
less wear on records and stylus, and superior sound at all
frequencies. Hear the "Golden Classic" GC -5 or GC -7 soon.
You'll agree they are a fitting climax to the famous General
Electric cartridge tradition.
-
151CC
5
-5
lo
IS
Plays both stereo and monaural records
Frequency response,
20 through 20,000 cycles
Output 8 my
Effective mass of
stylus about 2 milligrams
Lateral compliance 4 x 10-6 cm /dyne;
vertical compliance 2.5 x 10-s cm /dyne
Recommended tracking force with professional -type tone arm 2 to 4 grams. (Specifications for Model GC -5.)
Model GC -5 (shown) with .5 mil diamond stylus, $26.95.
Model GC -7 with .7 mil diamond stylus, $23.95. Model CL -7
with .7 mil synthetic sapphire stylus $16.95 (Manufacturer's suggested resale prices).
111:=
10
+
O to 15NC WESTRES STEREO IA
Io SOKC RCA MONAURAL I2.547
TEST RECORDS.
IS
+
100
I0KC
2011C
Smooth response on both stereo and mon-
aural records. Consistently high channel
separation, because the stylus is magnetically
linked to the coils.
TM -2G "Stereo Classic" tone arm
A professional-type tone arm designed for use with G -E stereo
cartridges as an integrated pickup system. Unusual two -step ad-
justment permits precise setting of tracking force from 0 to 6
grams. Lightweight, brushed aluminum construction minimizes
inertia. Statically balanced for minimum friction, reduced stylus
and record wear $29.95 (Manufacturer's suggested resale price).
GENERAL
AUDIO
ELECTRIC
See and hear the G -E "Stereo Classic" cartridges and
tone arm at your Hi -Fi dealer's now. For more information
and the name of your nearest dealer, write General
Electric Company, Specialty Electronic Components Dept.,
44A3, W. Genesee St., Auburn, New York.
MARCH, 1959
31
www.americanradiohistory.com
prevent minute iron particles from being
accumulated on the diaphragm by the
magnetic stray field. This protective
screen represents additional and mostly
unwanted acoustical elements. In the
equivalent circuit, these elements are
M4, R4 (the mass and the resistive component of the screen) and C4 (the volume between screen and diaphragm).
The magnitudes of these elements are
such that again the high -frequency response is undesirably affected. In most
cases a drop of high -frequency sensitivity and additional irregularities result.
Frequency -Response Improvement
These problems in the high-frequency
range of the conventional moving-coil
microphone have been solved in the design herein described by placing the
controlling resistance R, between sound
field and diaphragm. A schematic cross section of this microphone is shown at
(A) in Fig. 5.
The mechanical- acoustical system is
essentially the same as that of the conventional microphone except that the
controlling resistance R, is now interposed between diaphragm and sound
field. This resistance may take the form
of a narrow circular slot formed between an edge of the pole plate and a
solid cap. In the equivalent electrical
analogue, (B) of Fig. 5, M,C, again are
mass and compliance of the diaphragm
voice -coil assembly and C, is the compliance of the volume enclosed by the
case. R, is the resistive component of the
controlling resistance and M, the mass
associated with it. C, is the compliance
of the small volume between cap and
diaphragm coupling R,M, to the diaphragm.
The current I through M,C, which
C
again represents the velocity of the diaphragm will be independent of frequency as long as R, is large compared
with the reactive components M,C
M,C and as long as the reactive component of C, is large compared with the
impedances of the other elements. But
now, contrary to the conventional design, R2 is also effective at the higher
frequencies because it is always interposed between the sound field and the
diaphragm. It can be shown that even
the resonance between the diaphragm
mass M, and the coupling air volume C,
is sufficiently damped by this resistance.
It is further possible to choose the mass
component M, of the controlling resistance in such a way that an additional
resonance M,C, above the resonance of
the diaphragm M, and volume C, can be
obtained, thus extending the highfrequency range of the microphone. As
the narrow air gap of the acoustical
resistance is of the magnitude of a few
thousandths of an inch, it forms an
excellent protection for the diaphragm.
Therefore, no additional protective
means, with its disturbing acoustic elements, is required, as can be seen in Fig.
6. The new arrangement provides an
extremely smooth and extended high frequency response. Another means for
providing the acoustical damping resistance on the incident side of the diaphragm is through the use of felt at the
sound entrance. The significant difference between the use of felt and the
extremely narrow annular slot lies in
the ratio of mass to resistance of the
acoustical entrance. These two means
may be employed together to secure an
optimum combination. Felt used at the
sound entrance must be, of course, completely waterproof, and non -hygroscopic.
C
¡AAR?
POLE PLATE
POLE PIECE
AGNET
CI
1,1
I
i
MAGNET
STRUCTURE
C3
(B)
Fig. 5. (A), Schematic of microphone in which acoustic resistance is provided by
narrow annular slot, and (B), its equivalent circuit.
Fig. 6. Altec 680A "Acoustic Gate" micro-
phone using principles described in text.
A sintered bronze or sintered stainless
steel screen in the cap over the diaphragm is also used to form the resistance between the sound field and the
diaphragm, as seen in Fig. 7.
A serious restriction to the outdoor use
of microphones is their susceptibility to
wind noise. The excitation of a microphone by wind is due to three possible
sources. There may be pressure fluctuations in the wind stream due to fluctu-
ations of the stream velocity, or pressure
fluctuations may be produced by turbulence around the microphone. The extremely small sound entrance of the new
design allows the streamlining of the
microphone so that turbulence is safely
avoided, thereby eliminating one source.
Complete streamlining of the microphone, however, might result in a shape
which is not acceptable from the standpoint of appearance. The resistance in
front of the diaphragm between sound
field and the diaphragm provides another possibility of very effective wind
noise suppression. A cap of approximately 1,43-in. thickness made of felt of
medium density fitting snugly over the
head of the microphone not only suppesses turbulence effects, but also reduces wind noise due to velocity fluctuations. It has been found that a cap of
this kind gives a wind noise suppression
better than 20 db. If such a felt cap is
used, it should he remembered that the
opening of the hase tube has either to be
closed or protected by felt similar to
that applied to the head of the microphone because most of the wind noise
lies at the low end of the audio spectrum.
(Continual en page 85)
AUDIO
32
www.americanradiohistory.com
MARCH, 1959
C C C
G
E
S'cco Classic" Amplifer
Model MS4000
40 watts of balanced stereo power
. only $17995
cla
HARMONIC DISTORTION
General Electric's MS -4000 40 -watt Amplifier gives
you power to spare for clean stereo reproduction,
with less than 1% distortion. It offers 40 db or
higher channel separation, a rumble filter effective on all inputs, and maximum output stability
at all frequencies.
OUTPUT
2
ó5
o
OUTSTANDING PERFORMANCE FEATURES
Full, balanced 20 -watt output from each channel
Flat re(28 watts per channel music power)
sponse within 0.5 db from 20 to 20,000 cycles
Single -knob
Extremely low hum and noise level
controls for easy adjustment of both stereo chanContour control provides
nels at same time
smooth, gradual bass boost without apparent
change in sound intensity. Only $179.95*
MS -2000 (28 -watt Amplifier) $139.95*
--lo
Now you can change the stereo perspective without moving
from your chair! Two knobs permit adjustment of channel
balance and volume up to 30 feet from the amplifier.
Especially useful in stereo because of individual preferences
for channel balance and variations in room acoustics. May
also be used as volume control with monaural amplifier.
30 -foot cord included. $14.95*. *Manufacturer's suggested
resale prices.
See and hear the G -E "Stereo Classic" amplifier and tuner at
your Hi -Fi dealer's now. For more information and the name of
your nearest dealer, write General Electric Company, Specialty
Electronic Components Dept., 46A3, W. Genesee St., Auburn, N. Y.
20
22
25
BALANCE CONTROL
90
FADING TO AMP
RO
70
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eo
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F.-_
50
412
30
FADING TO AMP
-_-
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E
20
10
o
10
20
30
40
50
60
70
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90
100
7. CONTROL ROTATION
FREQUENCY RESPONSE
10.000
EREOUENCY
New G -E Remote
Control RG -1000
1R
MIDEREOUENCY POWER (WATTS/
100
For top stereo performance at a sensible price,
hear G.E.'s "Stereo Classic" Amplifier soon.
AUDIO
RATED
SINGLE CHANNEL
Z1/.
20 000
CPS
FM -A'1
Tuner FA -12
Receives even weak signals with unusually low distortion,
hum and noise level. No audible drift. Visual meter provides
center channel tuning of FM and maximum AM signal. RF
amplifier stage in both FM and AM increases sensitivity. FM
multiplex jack for stereo adaptor. Built-in AM antenna;
folded FM dipole included. $129.95*
GENERAL
ELECTRIC
33
MARCH, 1959
www.americanradiohistory.com
New York's Audio Workshop
SIDNEY NORINSKY
-or
Business opportunities are where you find
create -them.
is always room for an enterprising idea like this one.
And there
any familiar enterprise takes
stamina and perseverance. But to
open a brand new kind of business
based on an untried idea takes no small
additional measure of courage and imagination.
The two young men who founded New
York's Audio Workshop last May appear to have all of these virtues. Dave
14luirhead and Elliot Gordon opened this
unusual center in the belief that enthusiastic beginners in audio would welcome a place where they could receive
instructions and guidance in building
and testing their amplifiers, preamps,
tuners, and even complete systems. Experienced audiofans would have to be
attracted to the Workshop if it were to
grow in reputation.
Most important of all, Workshop atmosphere had to be relaxed, friendly.
Fees were to be modest, with test equipment, tools, and expert counsel thrown
in; electronic kits, as well as parts and
supplies would also be available.
To START
304
Middle Road, Hazlett, N. J.
They opened in a large, well -lit loft
one flight up at 732 Broadway, just opposite Waverly Place, a location which
abuts the New York University campus,
Greenwich Village, a bustling business
and industrial area, and which is also
convenient to two subways.
First objectives have been achieved.
Several slow starting months were followed by two important publicity breaks.
Articles in the Sunday New York Times
and in Cue magazine told millions of
readers about the Workshop. The response was heartening. Beginners and
experienced audio -ists began to appear
and now, nearly any night, half -a -dozen
and more people are to be seen seated
before the 22 -foot long worktable fitted
with individual goose-neck lamps and
power outlets at each work -place. They
work on kits, run frequency vs. power
and distortion checks on their gear, and
perform the inevitable hum- reduction
operations on stereo rigs.
Available to all are oscilloscopes, an
intermodulation meter, audio signal gena
Personal attention is a feature of the
Audio Workshop. Here Elliot Gordon
helps a Workshop "customer" over the
first stages of wiring a preamplifier.
erators with sine- and square-wave outputs, an r.f. generator, vacuum -tube
voltmeters, and a wattmeter calibrated
across 16 ohms. Some parts are also
maintained in stoek.
Who are the "Customers "?
Dave
Muirhead,
left,
and
Elliot
Gordon,
shown
before a section
of the long workbench, are partner- owners of the
Audio Workshop.
The people who come to the Audio
Workshop range from a transistor
specialist and editors of technical magazines, to a biochemistry researcher, a
physiotherapist, and a semi -retired bar
owner. "We have to teach many of them
to solder, and some don't know the difference between a resistor and a capacitor. But once they've started, they
generally raise their sights to more
powerful amplifiers or additional components and many begin to study basics
of electronics and audio" say both partners.
The projects in work at any time range
from simple wiring of a basic power
amplifier under close guidance from
Dave or Elliot, to the full- fledged development of a 3 -tube simplexed stereo
amplifier. Experimenters at the Workshop seem to have that healthy disdain
for authority, coupled with a belief in
their own ability and ingenuity, which
has kept the audio field fresh and exciting. For example, in December, 1958,
a Workshop denizen produced-lo and
behold
three dollar electrostatic
(Continued on page 75)
-a
AUDIO
34
www.americanradiohistory.com
MARCH, 1959
So much better, you can
the difference!
Model
X -101
Cabinet
$189.50'
$24.95'
THE
FISHER
STEREOPHONIC MASTER AUDIO CONTROL
and DUPLEX AMPLIFIER
INCOMPARABLE FEATURES
40 watts in stereo, 75 -watt peaks.
is BUT LOGICAL that only a high fidelity instrument
using the finest materials can produce the finest sound.
When you look inside THE FISHER X -101, you will see
an immaculate wiring and component layout -you will
see massive, low -flux density transformers, with interleaved windings to prevent hum and noise (and guarantee the power response that others cannot) -and you will
see the world's finest, low -tolerance capacitors and resistors. Compare the X -101- feature for feature and part
for part -and you will know instantly why it is outselling every other brand, regardless of price. Its superior
quality is obvious to the eye
irrefutable to the ear,
objective in design, to bring you the music INTACT ...
the music itself.
r
12 inputs for all stereo and monophonic program sources.
Record- Monitor facilities.
8- position
Function Selector: 78, LP,
RIAA -1, RIAA -2, Tape, Tuner, AUX -1,
AUX -2.
4- position
Output Selector: Reverse, for
transposing the two channels; Standard stereo; Channel A and Channel
B for two- speaker operation from
monophonic source.
Single -knob Channel Balance control.
...
Full- range, Bass and Treble controls.
Hum and noise, inaudible.
Rumble Filter. Loudness Control.
Hear The Music Itself
Hear THE FISHER!
WRITE TODAY FOR NEW STEREO BROCHURE!
-
*Slightly Higher in the Far We't
FISHER RADIO CORPORATION
21 -29
44th DRIVE
Export: Morhon Exporting Co-p., 458 Broadway, New York 13, N.
AUDIO
LONG ISLAND CITY I, N. Y.
Y.
MARCH, 1959
41
www.americanradiohistory.com
Transformer Distortion
DUNFORD KELLY
In two parts-Part 2
The causes of distortion in transformers are fairly well known to transformer engineers, but
there is little the user can do to avoid it. However, a thorough understanding of the parameters which cause distortion and the effect of core material, size, stacking, and operating
conditions will help engineer and experimenter alike in their choice and use of transformers.
THE CORE MATERIALS discussed have all
100K
Lln.wnelchlne tren4rmr,lote5004.. Core. Mo.. el (Ni 77.2%,
Gr 4.0%, Cr 13%, o 14.9%) 79 po. L-14 mi ooI'.n. Stack
17 awinetio chigh, 51714. 5044 cell, 345 gnu; 5004.w11,
1013 hems. Memured with 3004. mone m 500. wi1; 504. coi
unloaded. F ..4..ncr, 23 cps.
10K
lz 4.14.
been suitable for use in output transformers by virtue of high saturation
flux densities. The silicon steels saturate
at about 20,000 gauss, the 50% nickel
iron at about 16,000 gauss.
Another material of importance is
known as Mumetal s It is not useful in
output transformers, saturating at 8,000
gauss, but is superior at lower flux densities, having the highest permeability
of the lamination metals. It is the most
expensive and the most fragile, but in a
core completely free from air gaps, it
has initial and maximum permeabilities
2 to 4 times as great as 50% nickel iron
measured in the same form.
The Mumetal curves of Fig. 4 are not
Or-I o
-IS
Fr.lmncr
cp; solos ml.mnc..
26.64..
-_.
FEKMw ZiTY
I®
-5
-10
-15
NM!
10
10
100
Flux
DENSITY
-It
GAUSSES
(A)
Fig. 3. Curves
100
-
1000
100
100,000
1000
10,000
GAUSSES
are very similar in shape to the 4750
curves of Fig. 3 except for an 8,000 gauss saturation point instead of 16,000
gauss. This reduces the power -handling
capacity to one fourth that of the 4750
alloy, precluding output transformer use.
By coincidence, the low -level distortion
of the Mumetal is the same as for the
4750 alloy. This is because of the difference in test conditions. If this Mumetal had been measured in the EI-75
laminations of Fig. 3 the permeability
would have been about twice that of the
4750 alloy. The transmission loss in
decibels would have been about half as
great as Fig. 3 and the distortion about
half as much as Fig. 3 at low levels. At
high levels the Mumetal also produces
about half as much distortion as the 4750
if compared at half the flux density of
the 4750, due to the 2 to 1 ratio of saturation flux densities. The advantage of
Mumetal diminishes at higher levels. It
is not often used above 2,000 or 3,000
gauss.
It must be remembered that produc
00K
10K
É
z
E 1000
100
ó
100500
i
111
1II/,/f1
I
F...F.F.... F1....
Vl1
111111Ir//
=.F.F.FF.r'E
E1E111 I
NIiiERIIt/
ppil1\i..
ai.......mm...m.E/i ms..
/
ó
100
0400
ó
1.0
11
,.I
I
1
G
FIR
VOLTS
_\\I11IIeI
1\\:mrl11
tn
S.
inn
FLUX DENSITY
-
1nm
u
ROM
IDOS
GAUSSES
Fig. 4. Curves of transmission, permeability, distortion, and impedance vs. flux
density for Mumetal core material.
ONE
s sZ
'll.
10
0.,
51
2101
(A)
100-11w. coll.
Z 55.7.
,11-!:
hi
"¡isnIMI=1:111\
F,..
111I
1=
40A.
TRANSMISSION
10
dt.
1S
.-
Z
FLUX DENSITY
4638 10th Ave., Los Angeles 43, California.
8 Bulletin EM -16, " Allegneny Mumetal."
Allegneny Ludlum Steel Corp., Brackenridge, Pa.
Alley Ni 48%, F. 37%. 4,4- reck, 79 ge. I 75, Woowarming
locoed 100%, 04714. N,dieym annealed
11
AND
Not direct 1, e.aq..bl. .SIA Flp.1,2 and 3 beam
of Imp. sir go9 a d Mll.nnl Inp.das. nI.0op.
10
directly comparable with the first three
figures because the core is very much
smaller and the impedance relations are
different. This transformer was designed
for line matching. It is the small size
sometimes enclosed in microphone cases.
It was measured with one winding driven
by a source of rated impedance and the
other winding unloaded. This is not the
design condition for a line matching
transformer, but in the ordinary case
where the gain controls follow the first
stage of amplification, the line transformer is generally followed by an input transformer and the source is the
only loading resistance. This is the condition that was approximated.
The Mumetal distortion curves, Fig. 4,
14 50
,S
FEAMRAIILITY
..
11.1
- ..5...
n.1
1M11ry/1ME/
111I,NIII
F...F...F.F...F'.I/..
r111
S1
rln1I//1mil
iilliiiiiin1.-.iiiih1/l11
- -.. .ii:11111
... . .. . f I.. =..
5001
1
rI
1
01
usato
1n
\!\I I1
-
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of transmission, permeability, distortion, and impedance vs. flux
density for No. 4750 alloy core material.
tion variations for high -permeability
materials are large and cause corresponding variations in transformer characteristics.
The distortion of Fig. 4 is the actual
distortion produced by the transformer
at 25 cps when used in the usual manner. The distortion is much too high for
a good -quality sound channel, despite
the Mumetal core. To reduce the distortion the energizing current must be reduced. One approach is added turns on
the coil, but this means finer wire and
higher resistance loss. A larger core is a
more satisfactory solution. If the original coil resistance is duplicated, the
larger transformer has higher impedance
and reduced distortion.
Figure 7 is an example of a large
transformer with a Mumetal core. The
maximum low -level distortion is about
0.4 per cent third harmonic. This is much
improved over the 3 per cent third for
the small transformer. To accomplish
this improvement, along with improved
low- frequency response, and greater
power-handling capacity, the core of this
transformer weighs 40 tunes as much as
the core in the small transformer.
A line- matching transformer used in
an instrument was required to be nearly
distortionless. The measured low level
distortion peak was 0.08 per cent third
harmonic at 20 cps. The core of Mumetal
weighed 33 pounds. This huge core
was unavoidable if this low distortion
level at 20 cps were to be attained. Actually a really good power amplifier has
as low distortion at 20 cps .as this .one
transformer. This immense, very expen-
AUDIO
42
www.americanradiohistory.com
MARCH, 1959
I
I
must tell you, have heard a speaker system that
approaches the authenticity of concert hall performance."
"Now,
says Mischa Elman, the internationally renowned violinist, now celebrating the 50th anniversary
of his American debut. Mr. Elman is an artist whose preference for concert hall performance over
recorded music is a matter of public record. His enthusiasm after hearing the TMS-2 in his home is
shared by many other leading artists, musical authorities and audio experts who also subjected the
TMS.2 to critical listening tests under at -home conditions.
THIS IS IT!
University's
`Trimensiona l'
Stereo
Speaker
THE NEW
TMS -2
PATENT A'PLI ED FOR
A STEREO SPEAKER SYSTEM THAT COMBINES ...
Two complete speaker systems in one enclosure
TMS.2 with deflector doors
for monophonic use
closed
Here is the most significant loudspeaker
achievement since the advent of popular
stereo ... a University development which,
at last, actually eliminates ail the problems
of placement, space limitations, decor and
cost ... but most important of all, produces
a new kind of stereo sound ... the authenticity of concert hall depth.
COMPACT By utilizing the exclusive dual voice
coil feature of the C-I2HC woofer, only one bass
enclosure and woofer are required to handle the
entire low frequency range of both stereo channels. Extended, undistorted bass is superbly reproduced by making use of the RRL enclosure
design so successfully employed in University's
Ultra Linear Response systems. See fig. 1.
OWl VOICI
BASS
FIG. I
CO L
channel project sound from the sides of the cabinet. By adjusting the deflector doors, the amount
of stereo spread can be increased or decreased,
as desired, according to the nature of the program
full deflection for opera or major orchestral works. less deflection for chamber music
or soloist. By thus deflecting all frequencies, in
proper relationship, to the rear and side walls of
the room, multiple sound sources are created
that not only provide the otherwise missing
dimension of depth, but also preserve the stereo
effect virtually throughout the room. See fig. 2.
...
mE
or
CHANNEL N
FIG.
WnU
3
NIOOa
tNnLNCIn
rRnNNLIEr
NBA
/RnnNCas
CNLNNIL
L
/WM ANNLNRNL
C
R
REAUSTIC STEREO Unusual breadth, depth
and clarity of stereophonic sound is accomplished
by utilizing the walls of a room, just as the symphony orchestra uses the acoustical properties of
the concert hall. The woofer sound emanates
from the rear of the enclosure; specially designed
separate mid -range and tweeter units for each
AUDIO
tion to being used for balancing the system to
room acoustics and personal taste, these controls
and the deflectors may be adjusted to produce a
full, very pleasing stereo -like effect when using
monophonic program material. Whether you
start your high fidelity system with monophonic
equipment, or go right into a stereo setup, the
TMS -2 is the best investment you can make, because it is equally at home" with any kind of
program material, and no further additions to
the speaker system are ever required.
DESIGNED RIGHT- PRICED RIGHT Flawlessly
designed along simple, classical lines, beautifully
proportioned to compliment the most exacting
taste, the TMS -2 will enhance any decor. In fact,
it looks more like a piece of fine furniture than
a typical speaker cabinet. Breathtaking in its performance ... beyond the scope of conventional
store
L
CAROM
Unprecedented compactness -only 30"wide, 25" high, 121/2" deep
A third dimension to stereo sound ... DEPTH
Placement anywhere in a room
Use for both monophonic and stereophonic reproduction
Uncompromised quality at an attractive price
USE ANYWHERE The unique design of the
TMS-2 provides you with two distinct advantages: place it in a corner or anywhere along a
wall, by merely positioning the deflectors as
shown in fig. 3, and since there are no particularly
critical listening positions, you, your family,
your friends -any number of listeners -can enjoy
the TMS -2 from most anywhere in the room.
MONOPHONIC OR STEREOPHONIC With deflectors closed, the TMS -2 is an outstanding, widerange monophonic speaker system. "PRESENCE"
and "BRILLIANCE" controls are provided for both
sets of mid and high frequency speakers. In addi-
MARCH, 1959
monophonic or stereophonic reproduction, the
engineering concept of the TMS -2 eliminates redundant components; makes use of the latest,
most advanced acoustic principles. RESULT: the
ultimate in Uncompromised value. In Mahogany
-$258, Blonde or Walnut -$263, User Net.
See and hear the TMS-2 at your dealer
NOW!
You too, will agree with musical and audio experts that It marks one of the most extraordinary
advances In high fidel ty and stereo hlatoryl
...
UNIVERSITY LOUDSPEAKERS, INC., WHITE PLAINS, N.Y.
43
www.americanradiohistory.com
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Fig. 5. Curves of transmission, permeability, distortion, and impedance vs. flux den
city for Mumetal core with d.c. polarization.
sive transformer illustrates how nearly
impractical is a distortionless trans-
former.
The disparity in variations of amplifier and transformer distortion with
level is an important consideration. Amplifier distortion is measured at maximum power and usually drops rapidly
with reduction in signal. As a result,
the amplifier in use contributes very little distortion most of the time. In contrast, a line transformer functioning
over the range from a few gauss to a
few thousand gauss, distorts at all levels,
and in use distorts all signals at low
frequencies.
Direct Current Polarization
The effect of direct current in a transformer is intricate but will be briefly
considered. Audio transformers are
never required to carry direct current
when this can be easily avoided, but an
output transformer must usually carry
the direct current for its stage. In the
case of push -pull circuits, the direct
current largely balances in the transformer, subjecting the core only to the
unbalance current. This can be made
negligible and is generally ignored in
transformer design. In a single-ended
power- output stage the direct current is
equal to the largest alternating currents,
excepting overload, and profoundly
limits the low- frequency capability of
the transformer. With alternating currents alone, the core material contains
no flux at no signal. With sine wave excitation the core will saturate at the
same signal level with either instantaneous signal polarity. In contrast, direct
current biasing adds to one polarity of
alternating current and subtracts from
the other polarity, so that the core saturates first in the direction of additive
currents. Consequently direct current
polarization reduces the power handling
capacity of the core, because a part of
the magnetization range is no longer
utilized. Another consequence is a reduction in alternating current permeability,
due to partial saturation of the core.
If the transformer is constructed with
an interleaved core providing a minimum air gap and is tested both with and
without direct current, in the usual case
the transformer core is nearly saturated
by the amount of direct current required
by the amplifier stage. Therefore the inductance is drastically reduced. A partial remedy is an increased air gap. The
air gap regrettably adds to the reluctance
of the magnetic path, but it reduces the
direct current magnetization of the core
material. With substantial direct current
polarization, the added reluctance of the
air gap will be more than offset by the
decreased reluctance of the core material, providing a net increase in inductance.
The transformer of Fig. 4 is a size
now in use with transistors. In transistor
circuits, direct current is usually carried by the transformer. Figure 5 is of
the same transformer carrying 2.5 milliamperes of direct current. With the
direct current polarization, the low -level
alternating current permeability with
Mumetal is about twice as great as with
silicon steel, and about the same as with
4750 alloy. Calculating the proper air
gap with the direct current present° results in a figure of .0004" compared to
the actual .000128 ". The next larger gap
commonly used is the butt gap which
produces a minimum air gap on the
order of .003" with small laminations.
One intermediate gap size could be produced by interleaving the laminations
two by two, instead of one by one. This
should double the air gap, because only
half as much lapped surface would be
available. Gaps smaller than the butt
gap could be produced by coating the
laminations with insulating coatings of
proper thickness and interleaving them.
This is awkward and certainly not in
general use.
The .000128" gap in this core, although smaller than optimum, was not
altered. Thus the result of added direct
current is not obscured by other changes.
Direct current polarization adds the
even numbered unsymmetrical harmonics
to the odd numbered symmetrical ones
produced by alternating current alone.
The result, Fig. 5, is a horribly full harmonic spectrum. Beside the addition of
the even -numbered harmonics, the total
distortion is very much greater at all
flux densities above 100 gauss. The cause
of this excessive distortion is the asymmetry of polarized core material which
responds differently to the two polarities
of signal, and the reduced transformer
impedance which impresses a larger part
of the core distortion on the circuit.
The permeability, Fig. 5, with the
polarization is quite different from the
unpolarized permeability, Fig. 4. At low
flux densities the permeability is deter mined by the d.c. polarization, while at
the highest flux densities the polarization
has slight effect. In this case the low
level permeability is reduced from 6000
to 1600. This approximate ratio holds up
to about 2500 gauss, while the permeability is only slightly reduced at 6000
gauss. This reduction in low and moderate level permeability raises the low frequency cutoff in the same ratio, as
for example from 40 to 150 cps.
An output transformer for a 6V6 was
designed on the core of Fig. 1, using the
same material, Audio A silicon steel. The
low -level inductance, with the proper
.007" air gap, was 0.3 as great as the
inductance without d.c. and without an
air gap.
With single -ended audio output transformers of ordinary size, an inductance
decrease by a factor of three due to the
direct current and the appropriate air
gap, seems typical. In the region of
maximum permeability the decrease is
greater. To compensate completely for
this handicap, a much larger transformer
would be required. Even so, a large part
of the even -numbered harmonic distortion would remain. Direct current is
thoroughly undesirable in audio transformers.
.
Core Insensitivity to Frequency
The impedance of a coil is proportional to frequency, but the permeability
and distortion generation of core materials are largely unaffected by moderate
frequency changes. To verify this, Audio
A was tested first at 25 cps, then at 100
cps. Impedances were adjusted to the
same relative values at each frequency.
Both at 55 gauss and at 10,000 gauss,
the permeability and distortion decreased
less than one part in 20 due to this large
frequency increase. Eddy current losses,
which act as a distortionless shunt, increase with frequency, causing these
small permeability and distortion reductions. Higher permeabilities are more
frequency dependent, but for all practical purposes the core characteristics
measured at 25 cps apply to any low
audio frequency.
Distortion Variation with Frequency
"Magnetic Core Materials Practice,"
pp. 68-88. Allegheny Steel Company,
Brackenridge, Pa.
°
Figure 6 indicates the variation of
transformer characteristics with f reAUDIO
44
www.americanradiohistory.com
MARCH, 1959
THE TRIO, Model A -224, Stereo
:Amplifier actually embodies
-
LUS
three excellent instruments in
one handsome, compact unit.
The Trio is: A complete stereo
preamplifier with two separate
12 watt power amplifiers (24
watt peaks each.) A complete
24 watt monaural amplifier (48
watt peak.) A 24 watt monaural amplifier with complete stereo preamplifier arranged to
convert an existing monaural
amplifier to stereo. Outstanding
fil`
I
taiON,
features include: Separate
141411,:
ganged treble and bass controls,
balance control, mode switch,
speaker selector switch for local
and remote speaker systems,
contour control, tape output
for recording application and
rumble filter.
ALla
t l
THE TRIO, Model A -224 $99.95
the Cage (AC -24) optional 7.00
DUET, Model T -224,
Stereo Tuner: Monaural! Binaural! Whatever the application, this new tuner is designed
to give maximum performance.
A superb monaural tuner -the
T-224 incorporates separate AM
and FM channels for receiving
stereo broadcasts through this
one unit. Rear jack makes it
adaptable for multiplex reception.
While the DUET is an ideal AM/
FM monaural tuner-it's specifically designed for the growth in
stereo broadcasting. As stereo
broadcasting grows the value
of the DUET multiplies for you.
Costs just a few dollars more
THE
-
than conventional monaural
tuners! (The DUET incorporates
a simple indexing scale to per-
mit easy identification of five
pairs of "stereo" stations).
THE DUET, Model T -224
Harman -Kardon stereo instruments are the most
$114.95
flexible on the market today. Intelligent design assures
ease of operation. The new Duet stereo tuner and
Trio stereo amplifier
effective, inexpensive
- make stereo attractive,
- and sensible.
Prices slightly higher on the West Coast.
For additional information on HarmanKardon stereo and monaural units, simply send a postcard with the word stereo
on it to Harman-Kardon. Dept. A 3.
Westbury, N.Y.
harman kardon
MIES
AUDIO
MARCH, 1959
45
www.americanradiohistory.com
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Fig. 6. Curves showing transmission and
distortion on Audio A core material at
both high and low flux densities.
quency at constant voltage, or flux density inversely proportional to frequency.
This is the usual situation in audio equipment. At high flux densities the permeability increases with frequency, at low
flux densities it decreases with frequency.
High series resistances were used in
these measurements. They can be applied to lower circuit resistance applications by simple calculations.
The high -flux- density curves, 14,000
gauss at 25 cps, approximate the flux
density in a small, inexpensive push -pull
output transformer. At 25 cps the transmission is 0.20 and the third harmonic
is 59 per cent. At double the frequency
the transmission is 0.80 and the third
harmonic is 14.5 per cent. The higher
harmonics drop even more abruptly.
This very rapid improvement results
from a permeability increase with frequency accentuating the increasing inductive reactance.
The low -flux- density curves, 219 gauss
at 25 cps, typify input transformer operation. Doubling the 25 -cps frequency
moderately increases the transmission
from 0.45 to 0.60 but only slightly decreases the third harmonic from 5.4 per
cent to 4.5 per cent. The frequency effect is small because the increasing inductive reactance is diminished by the
decreasing permeability.
The two parts of Fig. 6 are indicative
of the most rapid and least rapid change
of characteristics with frequency likely
to be encountered.
Other Audio Core Materials
Beside the core materials previously
discussed, -others should' be mentioned.
The prospect for a material with a much
higher saturation flux density is very
poor. The best very- high -flux- density
material now available is an alloy of
cobalt and iron, Permendur or Hiperco,°
which saturates at nearly 24,000 gauss.
This material is very difficult to fabricate and very expensive. It has not been
used extensively in transformers. A related material, Supermendur, has the
same high saturation point combined
with lower core losses at very high flux
"Westinghouse Metals and Alloys,"
Westinghouse Electric Corp., East Pittsburgh, Pa.
e
densities than any other material. It
would be useful in high -level audio transformers except for a rectangular hysteresis loop which makes it extremely
non -linear.
Ferrites are magnetic oxides which
have very high volume resistivity, allowing the use of solid cores without excessive eddy losses. They are widely
used at frequencies above the audio
spectrum, but practically unused at
audio frequencies because of low permeability and limited power -handling capacity.
Many special core materials are used
for such applications as high-storagefactor inductances and magnetic amplifiers. They are generally unsuited for
audio transformer use. Perminvar and
Conpernik have nearly constant perineabilities at low levels, and are used in
precision inductances. Deltamax, Square
Permalloy, and Supermendur have rectangular hysteresis loops especially advantageous in magnetic amplifiers. Cores
of compressed powdered Molybdenum
Permalloy or iron are used in low loss
coils at audio and higher frequencies,
but have no particular merit in audio
transformers, because of low permeabilities.
Supermalloy
The lowest distortion and the highest
permeability at low levels is produced
by Supermalloy,10 a nickel -iron alloy
with additional ingredients. It is not
suitable for laminations due to the limitations on very high permeabilities imposed by air gaps, and because the material is highly sensitive to mechanical
strain. It is produced in tape form and
wound into gapless toroids. Coils for
such transformers must be wound by
hand or by toroid winding machines.
This material is used when the ultimate
in performance is required. It has an
initial perméability of at least 45,000
and a maximum permeability of several
hundred thousands. These figures are
several times as high as those for good
Mumetal. The saturation flux density isabout 7500 gauss, similar to Mumetal,
but the permeability peak is near 4500
gauss in contrast to a peak near 2000
gauss for Mumetal. Supermalloy accordingly retains its desirable proper
ties to higher levels than Mumetal.
A large Supermalloy core yielded far
the lowest distortion measured. The very
high permeability would cause this, but
additionally the magnetization curve is
more linear than the curves for the
lamination metals, further reducing the
distortion. Measured under conditions
equivalent to Figs. 1, 2 and 3 the third
harmonic was .08 per cent at 22 gauss,
0.18 per cent at 27 gauss, 0.26 per cent
at 1085 gauss, and 0.48 per cent at 5210
gauss. There was no low level distortion
peak. Due to the high permeability and
resultant high impedance the transmission was 99 per cent even at initial permeability. The cost of this transformer
was several hundred dollars.
Supermalloy will not generally displace Mumetal in low level transformers.
It is superb core material but it is too
difficult to use and too expensive.
Useful Relationships
When the physical constants of a
transformer are known, the distortion
can be determined from these curves by
making allowance for the relative circuit
impedances.
Even with nothing but the transformer
terminals available, useful distortion information can be deduced. Comparison
of the distortion and permeability curves
of Figs. 1 and 3 shows remarkable
similarity in shape, not absolute value,
although the materials are very different.
Even Fig. 4 for Mumetal has similarly
shaped distortion curves. The permeability curve for Mumetal measured with a
small air gap is also similar in shape
to Figs. 1 and 3. The measurements on
low -grade silicon iron
laminations
showed the same similarity. Excepting
grain oriented material, Fig. 2, which is
not in lamination form, the distortion
produced by high -level lamination materials depends on flux density and circuit impedances, and is largely independent of the type of core metal.
If the transformer impedance curve
is plotted at a constant frequency and
variable voltage, the point of highest
impedance is the peak of the permeability curve and can be referred to Fig. 1
for example, to determine distortion.
(If the core were grain oriented silicon,
the shape of the impedance curve would
immediately identify it. The peak would
be broader-, and closer to the saturation
point, and the slope would increase at
low flux densities, rather than decrease
as with the lamination materials.)
Measurements of the distortion components of the energizing currents were
.0001
10
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showing distortion vs. flux
density for low -level input transformer
with Mumetal core.
Fig. 7. Curves
AUDIO
-46
IA
d1i'll
AI11.I1
I
FLUX DENSITY
lo Bulletin TC -101A, "Properties of
Deltamax, 4 -79 Permalloy, and Supermalloy." Arnold Engineering Co., Marengo,
Ill.
ai
.rIli
MARCH, 1959
NOW, FROM GENERAL ELECTRIC'S NEW 6L6 -GC...
WATTS...with only
2% distortion without feedback*
55
...
Power for orchestral climaxes with full concert -hall brilliance
yet
mellow in tone, undistorted! You can build this high speaker power into
your new equipment at a cost one-third less than the cost of other tubes
with comparable performance!
With 30 watts plate dissipation, 5 watts screen, General Electric's
6L6 -GC beam pentode can take peak power demands in stride. This is a
new tube throughout, designed to handle easily the speaker requirements
of the finest audio systems. Type 6L6 -GC has, among other features:
Special 5 -layer bonded -metal plate, developed by General Electric for improved heat conduction and radiation.
New large heat radiator on control grid, to minimize grid emission.
Redesigned screen grid, for higher dissipation.
* Two
6L6 -GC tubes push -pull, Class
with 450 v on the plate.
AB1 service,
New protective slots on micas, to reduce high -voltage interelement leakage.
Key design -max ratings, per tube, of
the new General Electric 6L6 -GC are:
New -design bulb, to radiate heat more efficiently.
Top power output -low distortion -completely new design -economy!
Four important advantages to you of General Electric's 6L6 -GC. Ask any
G -E Receiving Tube Department office below for further information!
200 Main Avenue. Clifton, New Jersey
(Clifton) GRegory 3 -6387
(N.Y.C.) Wisconsin 7-4065, 6, 7, 8
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Chicago 41, Illinois
SPring
7
-1600
Plate voltage
Plate dissipation
Screen voltage
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GRanite 9- 7765.BRadshaw 2 -8566
73-ogress Is Our Most
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450 v
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Important Product
ELECTRkqp,
www.americanradiohistory.com
5
w
110 ma
EQUI PMENT
®e
.o
O
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O O
O
O
PROFI t
THE BELL "CARILLON" STEREO AMPLIFIER
YEARS AGO, long before announcement of the stereo disc heralded
a new era in audio reproduction, Bell
wa, one of the very first-perhaps the first
-to market an integrated stereo amplifier.
The Carillon is the latest succession to
Bell's original model and contains a number of refinements of features and design,
provides about three times as much power,
is good to listen to, just as good to look at
as handsome a unit as this reviewer has
seen), and, considering its power, is relatively light and compact.
The Carillon provides almost all the
special stereo features and functions that
can prove useful. There is a balance control, a master gain control, and a function
switch with three positions: stereo, reverse
stereo, and monophonic. The first two positions are self-explanatory. In the mono
mode, the two channels are combined, which
is desirable when playing a mono disc with
a stereo pickup, for this causes the audio
signals (lateral information) to add and
rumble (vertical) to cancel. If it is desired
to feed one source to both channels, the
function switch is set to mono and the
balance control is turned to one extreme
or the other, depending upon whether the
left or right source is to be cut off ; since
SEvERAL
the balance control permits infinite attenuation, this results in shutting off one source.
To balance the left channel against the
right all the way from the program source
(disc, tape, or tuner) to the sound emanating from each speaker, it is highly desirable to be able to alternate rapidly between
two conditions: left channel on and right
channel off; left channel off and right
channel on. The Carillon allows one to do
exactly this, although the instructions fail
to mention the fact. There is a speaker
switch that connects speaker A or speaker
B or both ; this applies to each channel.
The original purpose is to enable one to
connect an additional speaker, to each
channel for the den, playroom, or wherever. On the output terminal strip for
each channel, there are terminals marked A
and B, intended for the speaker in each
room. If instead one connects the left
stereo speaker to terminal A on one terminal strip, and the right stereo speaker to
terminal B on the other terminal strip,
switching between positions A and B will
alternate the sounds of the two speakers.
In the A-B position of the speaker switch,
both speakers will be on. (If one employs
the switch for balancing at high levels,
there is the possibility of damaging the
output transformers if their loads are
suddenly removed. Therefore it is advisable
to connect a 50 -ohm 10 -watt resistor across
each output transformer. Power consump-
tion by this resistor will be relatively
slight.)
The only significant omission in terms of
stereo functions is that of phase reversal.
Fortunately, this omission is easy to correct by installing a double -pole double throw switch at the speaker or elsewhere
to reverse leads to one of the speakers,
although for stereo records this function
no longer seems to be necessary.
For each channel, there are seven outputs. Three are high level, and two of
these -TUNER and TAPE AMPLIFIER-have
input level sets. The low -level inputs are
for high -impedance microphonic (magnetic), tape head, magnetic phono cartridge, and ceramic phono cartridge. Although ceramic pickups are actually high level, amplitude devices, in the Carillon the
signal from such a cartridge is fed through
a small capacitance, which in effect converts the cartridge into a low- level, velocity
device, so that the same preamplification
and equalization may be employed as for a
magnetic cartridge. The amplifier can accommodate either a ceramic or magnetic
pickup, but not both, inasmuch as the input
jack for each leads to the same point on
the selector switch.
There are no level sets for the low -level
inputs. To this reviewer's way of thinking,
a level set following the preamplifier stage
would be useful for equating the volume
obtained from a low -level source with that
from the high -level sources and for achieving balance between the two sections of a
stereo phono pickup (differences between
sections can be as much as 4 to 6 db) or
the two sections of a stereo tape head. Inasmuch as most tape amplifiers and most
tuners contain gain controls, which in a
pinch can serve the same purpose as input
level sets on the amplifier, it would seem
preferable if one of the two pairs of level
sets in the Carillon had been used for the
preamplifier section instead.
The Carillon follows the trend toward
separate rather than ganged tone controls,
permitting one to compensate for differing
tonal characteristics of unlike speaker systema, for different effects of room acoustics
upon each speaker, for different tonal
balance in each channel of the program
material, and so on. On the other hand, the
low filter for reducing rumble and the high
filter for reducing noise are ganged devices,
each one controlling both channels.
The Carillon is rated at 30 watts per
channel. This reviewer measured about 25
watts output at mid -frequencies before
clipping became apparent on an oscilloscope. The difference between 30 and 25
watts is quite minor, less than 1 db. At the
frequency extremes of 20 and 20,000 cycles,
each channel was able to deliver 20 watts
of a well- formed sine wave before clipping
occurred, and this is very good. Clipping
was symmetrical, and the amplifier gave no
sign of distress, such as oscillation or
radical change in waveform, when driven
into the clipping region -also very good.
Circuitry of the Carillon is straightforward and follows design principles of
proven worth. The unit may be termed an
"all-feedback" amplifier inasmuch as there
is feedback in the preamplifier (between
two sections of an ECC83 /12A %7) for
equalization, feedback in the following
stages (ECC83) in connection with tone
controls and the high filter, and feedback
from the output transformer over the remaining stages.
The left channel provides equalization
for the LP and "European" phono recording characteristics as well as for the RIAA
curve. The right channel supplies only
RIAA compensation. The thought is that
all stereo discs are recorded RIAA, so that
LP and European equalization are needed
only for mono discs, i.e., only for one
channel. But, as previously pointed out, the
best way to play mono discs with a stereo
cartridge is to parallel the outputs of both
cartridge sections in order to cancel vertical
rumble. However, if one sets the Carillon's
selector switch to the LP or European
position, equalization will instead be RIAA
on the right channel, with a consequent
tonal unbalance between channels. This
would be alleviated if the user switched
cartridges to a mono pickup (properly
wired to the head) when playing mono
records.
The high -level sources and the output of
the preamplifier stage feed into the selector
switch. Connected to the arm of the switch
are: an output jack for feeding a tape
recorder ; the low filter circuit; and the
high end of the volume control. The signal
goes from the arm of the volume control
to the balance control, to the function
switch, and to the first grid of the ECC83
associated with the tone controls and high
filter. Following this tube is the loudness
control and then the power amplifier section, using an ECC83 as a voltage amplifier
and split -load phase inverter. The output
stage employs 6CA7's connected in Ultra
Linear fashion and using cathode bias. This
results in less power output than with fixed
bias (some amplifiers obtain 50 watts and
more with 6CA7's), but on the other hand
one does not run the same risk of tube
destruction if the bias supply should fail.
All heaters but those of the output tubes
are d.c. operated. This is done by connecting the cathodes of all four output tubes
(for the two channels) in parallel and
running part of the cathode current through
the heaters, which are arranged in a series parallel configuration.
In a stereo amplifier, it is important not
only that each channel provide good performance in terms of frequency response,
distortion, equalization, etc., but also that
the two channels be very similar to each
other in performance characteristics. Following are measurements taken by this reviewer with respect to a number of functions, showing that on the whole the
Carillon maintains excellent correspondence between channels, along with very
creditable performance in absolute.
1. Treble controls. At 15,000 cps, the left
channel provided a maximum of 9 db boost
and a maximum of 21 db cut. For the right
channel, the respective figures were 10 db
and 20 db.
2. Bass controls. At 30 cps the left channel provided a maximum of 16 db boost
and a maximum of 18 db cut; the right
channel, 15 db and 19 db.
3. Master loudness control. Following
AUDIO
48
www.americanradiohistory.com
MARCH, 1959
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AD-2690M
netic phono input in BIAA position, 48 db
on tape head input, and 61 db on microphone input. Crosstalk between channels
measured 66 db isolation at 1000 cps, 61 db
at 50 cps, and 45 db at 10,000 cps.
As a final measurement, the reviewer fed
square waves into the amplifier and
viewed the output on an oscilloscope for
signs of ringing. None at all were evident
at 100 and 1000 cps, and only one slight
ripple was observed on a 10,000 -cps square
wave.
Fig. 1. Bell "Carillon "
-a
attenuation:
Attenuation
At 1000 cps
10 db
20
30
37.5
BOOST AT 50 CPS
Right
Channel
Ch
I
6.5 db
6 db
12
13
19
18.5
24
according to the reviewer's measurements).
This should be sufficient for virtually all
circumstances. Limited attenuation makes
it possible for the control to maintain the
excellent balance indicated by the above
figures. The importance of such balance
cannot be overemphasized.
4. Master gain control. Its ability to
maintain balance between channels was
very good on the whole, but, because it
permits infinite attenuation, not quite so
good as that of the master loudness control. During the first 5 db of attenuation,
balance in the reviewer's unit changed by
3.5 db, with the right channel dropping in
level below the left one. But between 5 db
and 55 db attenuation -which is apt to be
the working range 99 per cent of the time
-balance remained virtually within 2 db.
Thus if one were to adjust the balance
control for equality between channels with
the master gain control at mid-setting, one
would have inter-channel balance within 2
db at any normal setting of the gain control. It may be pointed out that even at 60
db attenuation, one would have balance
within 3.5 db.
5. Low filter. This provided the following
attenuation at selected frequencies:
ATTENUATION
Right
Left
I Channel
Ch
Fr
40 -cps position:
80 -cps position:
100 cps
.5 db
.5 db
40
20
200
4
100
2
40
20
4000 -cps
position:
25
Unlike most -other loudness controls,
which provide unlimited attenuation, the
Carillon's loudness control confines attenuation to a rated 40 db (actually 37.5 db
3
9
7.5
.5
7
13
.7
2
8
15
6. High filter. This provided the following attenuation at selected frequencies:
ATTENUATION
Right
Left
Frequency
8000 -cps
position:
Left
-
new stereo amplifier.
were the amounts of bass boost at 50 cps
relative to 1000 cps for various degrees of
Channel Channel
4,000 cps 1.5 db 2 db
10
10
8,000
15,000
15.5
15
2,000
4,000
8,000
15,000
1
8.5
16.5
21
0.5
7.5
15
19
7. RJAA equalization. The difference between channels was 2.5 db at 50 cps and
only 0.5 db at 10,000 cps. The maximum
absolute error was 3 db excess bass boost at
50 cps and 2 db insufficient treble cut at
10,000 cps.
8. NARTB (tape) equalization. The
difference between channels was 2 db at 50
cps and only 0.5 db at 15,000 cps. The
maximum absolute error was 3.5 db insufficient bass boost at 50 cps and 2 db insufficient treble cut at 15,000 cps. Since most
playback heads have at least 1 or 2 db loss
at 15,000 cps, the variation at the treble
end is of no consequence.
9. IM distortion. The following readings
were obtained at various amounts of
equivalent aine wave power, using 60 and
5000 cps in 4:1 ratio:
Equivalent
Sine Wave
Output
1
5
10
15
20
watt
IM DISTORTION
Right
Channel
Left
Channel
0.4 90
0.5
0.65
0.8
1.05
25
1.8
30
3.6
Considering the complexity of a stereo
amplifier, a well -written instruction book is
of considerable importance to the purchaser's successful use of the unit. The
Carillon comes with such a book, which
contains four drawings showing how to
connect one set of stereo speakers, how to
connect two sets of stereo speakers, how to
wire a complete stereo system to the
Carillon, and how to use the Carillon as a
monophonic 60 -watt amplifier. Even though
the booklet is written on a completely nontechnical level, it contains a schematic, a
laudable recognition of a fact of life
that any piece of audio equipment may
some day require servicing and that the
serviceman to whom the equipment is
brought may not have the schematic on
hand.
C -28
0.25 %
0.65
0.8
0.95
1.2
1.6
2.55
10. Sensitivity. As measured on the basis
of a signal fed into the tuner input and
with the master gain control full on, sensitivity on the right channel was about 1.5
db lower than on the left channel.
11. Frequency Response. With the tone
controls set to mid-position and with the
master gain control at maximum, frequency
response of each channel was extremely
flat, better than within 1 db, from 20 to
15,000 cps. With the gain control set for 6
db reduction in volume, the worst position
for high -frequency response, there was a
drop of 1.5 db at 10,000 cps.
Based on 25 watts output at 1000 cps,
the reviewer measured a signal to noise
ratio of 74 db on high -level input, which
is superior to the manufacturer's claim of
71 db. The ratio measured 55 db on mag-
KNIGHT -KIT 83YX776
STEREO PREAMPLIFIER
By their very nature, a stereophonic preamplifier must become a rather complicated
.device, when one considers the number of
individual tube circuits involved. About
the minimum number of stages required for
a monophonic preamplifier employing tone
controls is six-two for the phono preamp,
two triode sections for the tone -control
circuitry, an additional gain stage to make
up for the use of both level -set and loudness
controls, and a final stage as a cathode follower. Some configurations of circuitry reduce the total number of tubes required to
only two-a pentode preamp stage followed by a second pentode which is followed
in turn by the tone and volume controls.
Others make use of only two double triodes,
with four tube circuits. The majority of
control units, however, do employ six triode
sections, which makes for a simple straightforward design with plenty of isolation
between the various control circuits so that
there is no interaction. When the circuitry
is duplicated for etereo, there are then
twelve stages, and anyway you look at it,
this means a lot of connections.
The Knight -Kit Stereo Preamplifier
with the unlikely model number 83YX776
(actually a catalog number), employs this
type of circuitry, but does it in such a
manner that the work involved in putting
it together is reduced to a reasonable minimum. We have seen some complicated kits
which take as much as twice the construction time as this one. In addition to placing
most of the audio components on printed
wiring panela, Knight uses rotary switches
designed to "plug in" to the ready -made
panels, which reduces the work considerably. Instead of making connections to 45 of
the somewhat delicate terminals of wafer
switches-and with often more than one
connection to each terminal -the switches
are simply inserted into the ready- punched
holes and the projecting pins soldered to
the printed wiring. Not only does this simplify the work, but it also eliminates the
possibility of making wrong connections to
the switch terminals, which can be done
easily when as many as 36 or 48 terminals
appear on one switch.
-
AUDIO
50
www.americanradiohistory.com
MARCH, 1959
use this check list when selecting the
record changer for your stereo /mono
high fidelity system
RUMBLE, WOW AND FLUTTER -These
mechanical problems, especially
pertinent to stereo reproduction, require maximum attention to
design and engineering for suppression. Check the new GS -77.
RECORD CARE- Dropping record on moving turntable or disc during change cycle causes grinding of surfaces harmful to grooves.
Check Turntable Pause feature of new GS -77.
STYLUS PRESSURE -Too little causes distortion; too much may damage grooves. Check this feature of the new GS -77: difference in
stylus pressure between first and top record in stack does not
exceed 0.9 gram.
ARM RESONANCE
- Produces distortion and record damage. Cause:
improper arm design and damping. Check new GS -77 for arm
construction and observe acoustically isolated suspension.
HUM -Most often caused by ground loops developed between components. Check new GS -77 and note use of four leads to cartridge,
separate shields per pair.
MUTING -To
maintain absolute silence during change cycle both
channels must be muted. Check new GS-77 and note automatic
double muting switch, plus R/C network for squelching power
switch 'clicks.'
-
Stereo cartridge output signals are fed
to separate amplifier channels. Record changer should provide
facility for using both channels simultaneously with mono records.
Check new GS -77 Stereo /Mono switch.
STEREO /MONO OPERATION
These are just a few important criteria to guide you in selecting
the best record changer for your stereo and monaural hi -fi system.
Some of these features may be found in changers now on the
market, but only one changer incorporates them all -the modern
Glaser-Steers GS -77. Only $59.50 less cartridge.
GLASER- STEERS CORPORATION, 155 Oraton Street, Newark, N. J.
In Canada: Alex L. Clark, Ltd., Toronto, Ont. Export: M. Smoot, & Sons, loc., N. Y. C.
A-3.
GLASER- STEERS GS -77 THE MODERN RECORD CHANGER
superb for stereo ... and better than ever for monophonic records
AUDIO
MARCH, 1959
51
www.americanradiohistory.com
Circuit Description
Among its many features, the Knight -Kit
Stereo Preamp accommodates five pairs of
stereo inputs and four monophonic inputs
-the latter being arranged for three different types of pickups and for a microphone. Bass, treble, and volume controls
are clutch-type units which permit independent adjustment of each element simply
by holding one knob while turning the
other, though both may be turned together
as though they were conventional dual controls. Sharp cutoff scratch and rumble
filters are provided, and to minimize bum,
all heaters are operated on direct current.
From left to right, as shown in Fig. 2,
the controls are: selector equalizer, channel selector, bass, treble, level, and loudness /power. The slide switches are the
rumble and scratch filters.
The selector equalizer switch has four
stereo positions (tape head, phono, tuner,
and auxiliary), and seven mono positions
(microphone, and phono equalizations for
RIAA, European, 250 -cps crossover, ffrr,
old AES, and NAB). These monophonic
phono positions apply to the inputs labeled
GE, PICkering, and CERamic, and designed to accommodate medium and high level magnetic cartridges and the ceramic
types.
The second control from the left is the
channel selector, which has six positions
two for stereo and stereo reverse, two provide for individual channel operation with
the other channel inoperative, and two provide for outputs on both channels (monophonically) from inputs to either channel
A or B. This switch has 360 -deg. rotation.
The third and fourth controls are bass
and treble, respectively, followed by the
level control. These three controls have
separate knobs for each channel, and a soft
rubber washer between them serves as a
clutch and permits either independent or
common operation. The sixth control is
loudness, and is common to both channels.
The preamplifiers consist of dual triodes
with losser-type equalization between
stages. These are followed by the tone control pair which feed the level controls, and
the arms of the level controls feed the loudness controls. A gain stage and a cathode
follower, with feedback around both, come
next, with their outputs fed to the channel
selector, and its outputs are fed in turn to
the scratch filter and to dual output jacks
for each channel. The rumble filter works
only on phono and tape head inputs, and
consists of a two-section RC network in
each channel. The power supply consists of
a single -secondary transformer with se-
-
Fig. 2.
lenium rectifiers, followed by a low -resistance high -capacitance filter for the
heater circuit, with all six heaters and the
pilot light being fed in series; plate supply
is filtered by a conventional RC filter. One
a.c. receptacle is provided ahead of the
power switch, and another is switched. Line
noise is filtered from the primary circuit
by two .01-µf capacitors from line to
ground. Tape recorder feed jacks connect
ahead of tone and volume controls.
Level -set controls are provided for the
two tuner inputs, and a calibrated dual
control is used to set the phono pickup load
on the stereo phono inputs, with a range
from 5000 to 105,000 ohms. These three
controls are accessible from the bottom of
the unit, as is also the line fuse.
conventional manner. There are 106 resistors and 56 capacitors (one is a dual
ceramic and two are triple -section electrolytics, which makes 61 capacitors in effect),
so many connections are obviously necessary. Our construction time was just under
fifteen hours.
Aside from the circuit design, which we
consider to be excellently thought out and
to provide a high degree of flexibility in
switching, the physical layout of the unit
seems to be efficient. It is just possible
that it might be difficult to service in case
of any part failure or in case of a mistake
in construction. Fortunately, the instructions are extremely clear, and our test unit
performed perfectly from the first time it
was turned on.
Construction
Performance
Performance measurements made include
input levels for a 1 -volt output; frequency
response curves for the various types of
equalization (both stereo and mono inputs
were checked), including tone and loudness
controls; frequency response of the rumble
and scratch filter; crosstalk between channels; and harmonic distortion at a 1 -volt
output.
While specifications claim a sensitivity
of 2.5 mv for tape -head and phono inputs,
we measured both at a sensitivity of 1.85
mv for a 1 -volt output, and with a hwn
and noise output of 64 db below 1 volt.
Sensitivity of the ceramic phono input was
measured at 65 mv for 1 volt output, the
sanie output was obtained from the auxiliary input from a 500 -mv signal, and from
a 150 -mv signal at the tuner input with
the level-set control at maximum. On the
monophonic inputs, the "GE" jack required
a 1.9 -mv signal and the "Pickering" jack
required a 5.7 -mv signal for the standard
1 -volt output; the microphone jack required a 25 -mv signal for the same output.
As to frequency response, the "flat" inputs (auxiliary and tuner) were flat within
0.5 db from 10 to 100,000 cps. All equalized
inputs were within + 2 db of the standard
throughout, and differences between channels were less than 2 db. Level differences
between channels did not exceed 3 db anywhere except at the extremely low settings
where they reached 6 db in the worst condition. Tone control curves were within 3
db on both channels, and loudness control
compensation was within ±4 db at the
measured points -20, 30, and 40 db below
maximum output. Hum and noise on the
high -level inputs was 82 db below 1 volt.
Crosstalk was measured at 42 db at 1000
cps, and 35 db at 10,000 cps.
The rumble filter provides a cutoff of
approximately 5.5 db/octave below 100
cps, and the two curves were within 2 db.
The scratch filter-which consists of a
choke and capacitor circuit -gives a 10
db /octave attenuation beginning at 2500
cps, and both channels were within 4 db
of each other at 6000 cps, within 6 db at
10,000 cps. Harmonic distortion was measured only on the "fiat" inputs, and was 0.2
per cent at 1 volt output, reaching L1 per
cent at a 3 -volt output signal.
The tube complement includes two 12AY7
tubes for the preamplifiers, with four
12AU7's making up the remainder of the
circuit.
At its relatively low price and reasonable
construction time, this preamplifier offers
practically any feature that could be desired. We might have preferred the addition of a phase reversal switch six months
ago, but they do not seem to be so necessary now, since records all seem to be
O-29
standardized.
The Knight -Kit Preamplifier is housed
in a crackle -finished metal cabinet 1314 in.
long, 8 in. deep, and 41/4 in. high, phis
another a/4 in for the brass legs. The front
panel is aluminum, with a "graph- paper"
design, and knobs are black with chromium plated inserts. The back of the cabinet is
perforated metal, and in an operating position no jacks or connections are visible
from the rear. All connections are made
on a small sloping panel in a recessed area
in the bottom of the cabinet, so that for
table -top use all cables could be brought up
through a hole in the supporting surface
and none would show anywhere. This would
also apply when installing the unit in a
bookcase, for example, with the leads carried through the shelf behind the books on
the next shelf below.
Aside from the power supply, the input
and output jacks, and the volume and tone
controls, practically all of the component
parts are mounted on the printed wiring
panels. There are two of these, one carrying the six amplifier tubes and most of
plate and cathode resistors and the coupling
capacitors, while the other carries the two
switches, and the equalizing- network components. The two panels are assembled
separately, and interconnections between
the panels and the other elements of the
preamplifier are made after the panels are
mounted in place. The tubes mount in a
vertical position, and are accessible by
turning the cabinet over. The power -supply
section is housed in a separately shielded
section of the chassis.
There are some 355 separate operations
to the assembly of this unit, which is less
than half of what would be expected from
equivalent circuitry if assembled in the
Knight -Kit Stereo Preamplifier.
AUDIO
52
www.americanradiohistory.com
MARCH, 1959
NEW!
COMPLETE,
VERSATILE
the new PILOT 245 -A (successor to the 245) is the
world's most complete, most versatile quality stereophonic
preamplifier-amplifier. Among its truly unique, advanced
features are:
NEW! PILOT TROLOK permits adjustment of the separate bass and treble controls for each channel simultaneously
or individually, at the option of the user.
NEW! TURNTABLE /RECORD CHANGER SWITCH. enables
you to connect both a record changer and turntable to
the 245 -A
NEW t SEVEN PAIRS OF INPUTS for all stereophonic or
monophonic sources including inputs for a Multiplex adaptor for FM-FM stereo.
NEW! SPEAKER SELECTOR CONTROL allows you to add
a set of extension speakers elsewhere in your home and
select either main or extension system, or both.
NEW ! ELECTRONIC CROSSOVER feeds low frequencies
to Channel A and high frequencies to Channel B for monophonic bi- amplifier use.
Exclusive PILOT AUTOMATIC SHUTOFF turns off your
complete system when the changer stops after the last rec ord has been played.
Dramatic Design brushed brass escutcheon with gold
plated frame and heavy duty knobs.
Complete with attractive, black vinyl -clad steel enclosure.
CLEARLY,
-
STEREOPHONIC
-
PREAMPLIFIERAMPLIFIER
-
-
Pilot
245 -A
-
practical features are superbly supported by
performance and specifications of the highest caliber. The
new PILOT 245 -A delivers 40 watts total output on music
wave forms (80 watts peak). Frequency response is ±1 db
from 20 to 20,000 cycles. Harmonic distortion is less than
%. The seven pairs of inputs include MICROPHONE, TAPE
HEAD. RECORD CHANGER, TURNTABLE, FM -AM, MULTIPLEX and
TAPE RECORDER. Front panel controls include SELECTOR,
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37 -04 36th
STREET
MARCH, 1959
LONG ISLAND CITY 1, N. Y.
53
www.americanradiohistory.com
EDWARD TATNALL CANBY
Scouts Wha ha' wi' Canby Bled
NOTE:
It's been a while since I called in
my helpful Scouts to assist me in wading
through the piles of worthy new records
that come in on the daily tide from the
Post Office. Stereo sort of balled things
up last fall and the pickings were thin all
the way around -but suddenly, in December, the industry got its wind back and
WHAMI the biggest load of new records I
ever staggered under began to pile up for
Xmas. It was sparked by London's shipment of more than fifty stereo discs just
for that one month. Phew!
Scouts I and II aren't yet equipped for
stereo. In this they are simply statistically
typical of many record listeners. Scout I,
it turned out, had a GE VR II cartridge
in his system and, after some consultation
with advisers who shall remain anonymous,
I decided to risk all and let him play my
stereo discs as though they were monophonic, via the GE. It seems to have
worked; no damage noticeable so far. His
judgments are strictly non-stereo -but
after all, there still remains the content
of a record to judge, stereo or no.
As a matter of fact, Scout I's success in
playing and enjoying a large batch of
stereo discs via a wholly mono system can
be taken as a reassurance by some of our
more hesitant listener -readers. It's quite
possible, you see, with some cartridges.
Scout II, on the other hand, turned up a
different situation. I tossed him a couple
of stereo discs (expendable) and said see
what happens. Horrors! He came back
presently and said the sound was sort of
fuzzy and he didn't like it as much as his
regular records. I went over to check and
ouch! he was using a mono cartridge with
about as much vertical compliance as a
flat tire, or maybe a wheel without a tire.
The stereo disc screetched like a train on
a curve and for just as good reason.
Now, we're installing a stereo cartridge
in Scout II's mono system, connected in
parallel, mono -style (removing the vertical
response) and all will be well, monophonically at least.
I've launched a stereo conversion cam paign on both Scouts but have got absolutely nowhere. Maybe later, they both
say; it's too much trouble now. And is it
worth it I'll keep on trying.
E. T. C.
1. THRU LONDON
SCOUT
WITH
I
Espana ( Rimsky- Korsakoff: Capr. Espagnol; Granados: Andalusia; Chabrier:
Espana; Moszkowski: Spanish Dances.)
London Symphony, Argenta.
London CS 6006 stereo
Berlioz: Symphonie Fantastique. Paris
Conservatory Orch., Argenta.
London CS 6025 stereo
Falla: El Sombrero de Tres Picos (Three Cornered Hat). Turina: Sinfonia Sevillana. Orquesta Nacional de Espana,
Argenta.
London CS 6050 stereo
The young Spanish conductor Ataulfo Argenta died recently and has had many a fulsome eulogy since. As I hear him on discs, his
Spanish music Is tremendously good, his
French music often excellent, but his German
and other music isn't outstanding to my ear
by any means.
Scout I, ploughing through all this Argenta,
is enthusiastic about his "'three Cornered
Hat" recording, calling it "a fitting memorial
to the blazing talents of Ataulfo Argenta,"
and he doesn't think such other conductors of
the same music as Mitropoulos and Jean
Martinon can even approximate the "inner
pulse, the insinuating beat and shape" of
Argenta's performance here. As for the Purina
piece on the same disc, a pleasant bit of minor
Spanish entertainment, Scout I says it "sounds
like a million pesos," which ought to be
plenty for you and me. All in all, this is likely
to be a top -rank Spanish record -and be sure
to look up others by Argenta in the same
series.
However, Argenta's "Symphonie Fantastique," full of pep in the loud, brilliant outer
movements, as Scout I has It is finicky In
detall, uncertain, ill -defined, in the inner slow
movement and the waltz movement. Considering the dozens of competing versions, this
is not exactly a three -star recommendation.
As for the light- hearted record entitled
"Espana," Scout I -full of metaphor -says of
the Chabrier "Espafla", one of its items, that
it "is more redolent of the faubourg than the
plaza." By which he means, in case you don't
get it, that the playing is more French than
Spanish in style. This is all right with me ;
for, after all, Chabrier was French. The
Rimsky-Korsakoff "Capriccio Espagnol," says
Scout I, thrusting his metaphor to the hilt, is
"more evocative of the Neva than the (ugh)
Guadalquivir." (The ugh is mine.) "And so,"
he concludes, "Argenta has delineated this
light, harmless music exactly as it is. .
which leaves me floundering somewhere near
the mouth of the Volga, or maybe the Mississippi. Clear as mud, but the disc sounds Ilke
a real hot one, anyhow.
Tchaikowsky: Violin Concerto. Campoli;
London Symphony, Argenta.
London CS 6011 stereo
Mendelssohn: Violin Concerto. Bruch:
Violin Concerto #1. Ruggiero Ricci;
London Symphony, Gamba.
London CS 6010 stereo
Phew As is easily to be seen, London set
out to compass Just about the entire conven!
"780 Greenwich St., New York 11, N. Y.
tional concert repertory in its massive initial
stereo releases. Scout I is a blessing to me,
for I am, at this point, simply unable to take
in more than a few of these well -aged war
horses at a time. He thrives on 'em -and so,
I suppose, will many a record buyer.
For your information (In case you are the
thriving sort), the Campoli version of Tchnikowsky's. concerto ranks high, but not tops,
according to Scout I. He prefers (stereo aside)
the versions by Erika Morini (Westminster)
and Heifetz (RCA Victor) as the top two;
they are more penetrating, especially In the
slow movement where, he feels, Campoli is
pretty perfunctory. (Nothing, but nothing, Is
worse than a casual, perfunctory approach to
Tchaikowsky )
If you'd like to quibble about this-then go
right ahead : there are exactly twenty-six
different standard LP recordings of the concerto in last December's Schwann catalogue,
including six by Oistrakh, one by his son Igor
Oistrakh and three by Heifetz I (On second
glance, you'll find that these boil down to
about two thirds as many, the Oistrakh recordings being actually only two -one of them
apparently issued on no less than four different labels, of which perhaps one is licensed
by Leeds, the official Russian import concern.)
To go back to Campoli, I remember some
earlier recording of his with considerable
pleasure ; he has a fabulously expert Italian
techntque, clean as a whistle, plays rather
coolly but with fire, is extremely accurate and
is apt to please those of us who get annoyed
at too many viollnistic tricks. Argenta, the
late young Spaniard, "whips up a climax"
here and there in this recording but, as Scout
I has it, the composer himself probably
wouldn't mind this too much.
Mendelssohn -Bruch is a favorite London
combination, the earlier ffrr disc of the same
being already reissued on the low- priced Richmond label; this replaces it. These two performances are "in every way superior to the
earlier ones," says Scout I. Ricci, I will add,
is a first rate fiddler with a superb musical
ear and a very true sense of pitch, a classic
accuracy of technique and, if I am right, considerably more warmth than Campoli. Scout
I likes the way that the youthful Pierino
Gamba gets the London strings to sing out
with Mendelssohn, too.
!
Chopin -Douglas:
La
Source.
Ma a g.
London CS 6026 stereo
This is the sort of disc about which I find
I never can think of anything to say of any
great importance ; just some nice, old fashioned ballet music. Scout I seems to have had
a similar reaction. I can't figure out what he
meant. The music of "La Source" he says is
"not as dimensionally realized as later works"
(by Delibes)- whatever that may mean ; but
he does opine that Delibes as a ballet composer is second only to Tchaikowsky, and I'll
go along with him there. Delibes writes lovely,
easy, listenable French ballet music. What's
more, it's my expectation that the Paris
Conservatory Orchestra ought to be about as
AUDIO
54.
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Sylphides. Delibes:
Conservatory Orch.,
Les
Paris
MARCH, 1959
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good a bet as any orchestra the world over
for this particular music. It should be lovely
in stereo. too, and especially lovely in fias
stereo, with its emphasis on sharp, clean
m
string sound.
The familiar "Les Sylphides" music of
Chopin Iras been fixed up for orchestre (from
piano originals) by varions musicians, including Stravinsky. Titis is a British version
which, Scout I continues cryptically, "smells
of horse hair and patchouli." He's not sure
whether Mr. Douglas, the British arranger, or
the conductor, Peter Maag, is responsible:
hut what I want to know is, what is patchouli?
`6,
1,
4E2,
Brahms: Symphonies
(separately). Vienna Philharmonic,
#3.
Ku-
belik.
t
London CS 6016, 6004, 6022, stereo
Dvorak: Symphony
5 ( "New World ").
Vienna Philharmonic, Kubelik.
London CS 6020, stereo
One of the most interesting geographical
contrasts. musically speaking, is that which
we keep hearing over and over again on discs.
between the North German music rankers and
those of South Germany and Austria -notably
Vienna. Maybe they don't even notice It themselves, but as we hear it, the North Germans
do a lean, lithe, tempered job on music such
as Schubert, Brahms, Mozart. whereas the
Viennese school of performance (symphonic,
choral. operatic, chamber music or what have
you) tends towards n solemn, measured, slow
presentation, somewhat heavy-handed (to our
ears, that is) and yet very musical.
I tossed these four Vienna Philharmonic
disca to Scout I with this in mind, to see
what would happen to the Vienna Philharmonic under the Czech -ancestry conductor who
uvas briefly at Chicago a few years back. 'Twas
just as I expected.
Of the Brahms Third, Scout I says "unhurried, untense
phrase carefully moulded
on phrase
this is grave Brahms, occasionally bordering on the portentous." But he
likes the playing oil the same, reacting rightly
to the highly musical feeling of good Viennese
playing. The Second of Brahms which, he
says, can have a certain sunny innocence and
exuberance to it (I agree). here follows "a
grave, dark -hued path." The First Symphony,
too, is played with a "very deliberate appronch, not much in key with current tostes
but
legitimate."
And there you have the key to these London Brahms discs, for Scout I also praises
the beautiful sound of the orchestra and the
fine recording. If you like the mensured,
serious, weighty, yet musical Viennese approach, you'll find that Kubelik goes along
with it and with the Viennese orchestra here.
The Dvorak "New World," with the same
forces, has "the most deeply felt, beautifully
projected second movement these ears know"
-Scout I'a ears-and he suggests merely
that in other parts of the symphony Kubelik
lets his orchestra get a bit out of control in
an enthusiastic way.
No doubt about it, Kubelik does well in the
Central European tradition. Maybe that's
what was the matter when he was nt Chicago.
There, they like things snappy. They have
Reiner now, who plays all of this musle, and
most else too, with the steel whip approach
that seems so popular in these United States.
Take your chrce.
... ...
...
Brahms: Variations on a Theme of
Haydn; Academic Festival Overture;
Tragic Overture. Vienna Philharmonic,
Knappertsbusch.
London CS 6030 stereo
Beethoven: Piano Concerto 4:k5 ( "Emperor"). Clifford Curzon; Vienna Phil-
harmonic, Knappertsbusch.
London CS 6019 stereo
And here's another case of Viennese performing, with a conductor who, Scout I says,
is addicted to even slower tempi than anybody, anywhere.
Take a slow -speed -minded conductor and a
slow -speed orchestra and what do you get? In
Brahma, at least, you have yourself a great,
solemn, dark -brown effect, like an old fash-
toned Victorian mansion with stained glass
windows and polished wood -that's my own
idea. Scout I doesn't see how this conductor
with the crackly name, Koappertsbusch, can
get away with it; he thinks that Fürtwüngler
used to be able to do it this way because of
his method of "building front the inside"
quite right -but he finds that the Knappertsbusch readings are "endless and dreary beyond salvage, not recommendable."
Well, I'd go a bit slow on that, myself. As
explained above, there is a Viennese and
South German tradition that takes much of
this sort of music nt what seems at first to
us to be very slow speeds. Not all of the
playing is dull, by any means. Even Knappertsbusch. Just don't expect any Toscanini
lightning here, and if you can take the leisurely effects, you'll find this disc pleasing,
though not as good a bet as the Kubelik
Brahms above.
Beethoven's greater energy, plus a good
pianist, seems to have made n better thing of
the other Knappertsbusch disc. the Beethoven
"Emperor" Concerto with Clifford Curzon.
Scout I likes this one, finds it a "gravely songful reading of many felicities" though it
probably won't please everybody. I suggest it
probably won't piense those, again, who like
high -tension, powerhouse Beethoven in the
Toscanini- Horowitz manner. Something for
everyone, though, and this record, in addition
to a clear and well- styled approach, has
pianistic glitter and masculinity, excellent
teamwork between conductor and pianist, and
good sound balance in the recording. So says
Scout I.
Never forget that Beethoven, though from
Bonn, spent most of his life in Vienna, where
this music cornea from.
-
Rimsky- Kofsakoff: Scheherezade. Paris
Conservatory Orch., Ansermet.
London CS 6018 stereo
Stravinsky: The Firebird. L'Orch. de la
Suisse Romande, Ansermet.
London CS 6017 stereo
The bearded Ansermet is now re-doing just
about everything he ever did, in the new
stereo format- thereby keeping London's
catalogue lists jumping madly. Here are two
in interesting contrast. With the Paria
orchestra, Ansermet evidently shows his
strongest French side-his own habitat is
French Switzerland-and as an outstanding
elder statesman of conducting makes the
French players turn out their characteristic
best. Scout I thinks this is a terrific "Scbeberezade ": "The sound is stunningly articulate, the orchestral attack is highly disciplined, its tone so smooth it would seem to
be homogenized . . ." Well, if you can take
that metaphor in your stride, you'll likely find
you agree with his ears -and London's stereo
should do wonders for "Scheiterezade" and
all its orchestral glitter.
As for the Firebird (sometimes called the
Fire Bird in this slightly inconsistently
spelled recording) there's a different story,
one that makes sense to me. Scout I feels that
Ansermet's "bird" is a lyric one, all polished
and pastel colors, suavely played ; he doesn't
think this goes down too well as far as
Stravinsky is concerned -would rather hear
Bernstein or Mitropoulos sail foto it, for more
pep.
I think I know what Scout I means, but I'm
not so sure about Bernstein -who does a
rather old- fashioned sounding job on Firebird.
(It is an old fashioned piece to him, after oil.)
Ansermet takes all this early Stravinsky in a
style that may have been radical in its day
he did the first performances of n number of
these works-but which for our ears tends to
sound too soft, too lush, too Romantic.
Well, maybe not for your ears, whoever you
may be. I suspect that most listeners who
want to acquire another "Fire Bird" will find
this one just what the doctor ordered. If.
however, you prefer a more modern -sounding
approach, steer away.
-
Rossini- Respighi: La Boutique Fantasque.
Dukas: L'Apprenti Sorcier. Israel Philharmonic, Solti.
London CS 6005 stereo
Scout I took over large numbers of the
fifty -odd stereo (lises London threw out last
AUDIO
56
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MARCH, 1959
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Tchaikowsky: Symphony 4;k6 ("Pathstique"). Vienna Philharmonic, Martinon.
London CS 6052 stereo
This is one of those odd projects that London occasionally sets going
purebn d
Viennese orchestra, the Viennese orchestra,
led by a thoroughly French conductor, in a
Russian symphony With all this, what would
you expect? The results are "startling, if
nothing more"-which is not exactly top
praise from Scout I. The old warhorse gets
pulled and pushed about "like taffy candy"
but, he thinks, this happens most of the time
anyhow to the "Pathétique" these days. (I
agree, again). The sound 1s lustrous here, the
playing full of ardor. Not too bad, I'd say.
-a
!
Tchaikowsky: 1812 Overture; Marche
Slav; Capriccio Italien. London Symphony, Alwyn; Band of the Grenadier
Guards.
London CS 6038 stereo
As Scout I says, these "purple old essays"
are an inevitability for the well- adjusted
stereo set. As almost anybody knows, too, the
"1812" depends mainly on cannon power for its
stereo (not to mention mono) effect. The
louder the real, live cannon, the better the
1812.
Well, I haven't been in a cannon -fodder
mood lately so I haven't tried either this one
or the Mercury 1812, Mark II, the new one in
stereo. But maybe Scout I will put you on
the right track when he says that (a) the
results here; in London's version- including
cannon, bells, brass-are "staggering ;" and
(b) that London's cannon sounds "much more
modern than Mercury's period piece."
Now Mercury went to a lot of trouble to
round up its authentic Napoleonic cannons,
right out of the 1812 era. If London has gone
and used, maybe. a World War I monster,
perhaps Big Bertha herself, it's downright
unfair. Unless, of course, you want an even
BIGGER noise than 1812. If so, you'd better
get this one. Throw in n couple of new fifteen inch woofers and a pair of corner horns, while
you're at it.
2. SCOUT II IN HIGH
CLASSICS
New
Address
December (and plenty more since) with never
a bat of his eye. Played straight through 'em.
So I'll continue with some of the proceeds of
his playing.
This well known piece of re- written Rossini, decked out in fancy Respiglut orchestration, gets, according to Scout I, a "strongly
rhythmed, arresting performance with a personality of its own." The Israel orchestra is
best in its strings, he thinks, and these are
played up in the recording, for a slightly un.
balanced effect that, however, works out fine
in the listening. (I suspect, myself, that this
has to do with the traditional "ffrr" string
recording, always brilliant, here in its new
"ffss" stereo form and sounding much the
same ns always.) The familiar "Sorcerer" is
a "bang-up Job" in Scout I's book, highly
colored too, with proper drive and force.
The "Boutique" is played complete, on a
side and n half the leftover half, a bit less,
is enough for the Dukas.
0.
Box 629,
Mineola, N. Y.
Brahms: Piano Concerto 44.1. Leon
Fleisher; Cleveland Orch., Szell.
Columbia BC 1003 stereo
I sent this on to my high -classic repertory
man, Scout II, after I had played it myself.
Just out of curiosity. I had found it unexpectedly (the performers not being super famous) to be perhaps the finest Brahms
recording of the last ten years. Terrific. I
listened in stereo, of course, and was mightily
pleased, too, at the very professional competence of Columbia's concerto sound, with a
big but not too big piano, balanced for conveying an optimum musical intelligence in the
listening.
Well, Scout II begins his report "SUPERB !"
So you see, sometimes people do agree on
musical performance. "The very first note tells
you the story," he says, "a real roaring-bear
Brahms, growling and gnashing his teeth.
íxquiaite in the slow movement !" More
adjectives. then. "The pianist is real terrif !
So is Szell. Do you have an extra copy of this
anywhere ?"
Enough said. Just keep watching this
young Leon Fleisher, though, and keep an eye
on George Szell when he conducts the North
German type of music, and even the Viennese.
IIe combines a real feeling for those areas (he
comes from thereabouts) with an overlay of
American efficiency that makes his Brahmstype language easier for us to follow than.
say, that of Knappertsbusch, as reviewed
above.
Sibelius:
Symphony
www.americanradiohistory.com
Phila.
Orch.,
Columbia MS 6024 stereo
This, too, I had played myself, but sent it
on for curiosity and double- check. Scout II, in
his particular area of musical knowledge,
seems to be an automatic reflection of my own
feelings -which is just fine. This is the most
Tchaikowsky-like of all the Sibelius symphonies, full of expertly effective, big-style Romanticism plus lots of the famed "Northern"
sound of the Finnish composer. I thought
Ormandy did a marvellous job at revivifying
n sort of music that is getting pretty dated
now and can easily be hashed into sheer
bombast by a less expert conductor.
Says Scout II : "A fulsome, beautifully
phrased performance. Even this war horse
...
takes on life when given a chance
Big and
grand in the sound, yet nicely controlled
pulsated intelligently." Which is to say, it is
full of expression, but expertly done. "Most
of all, it gives you a chance to hear the inside
workings of the piece, and Sibelius gains by
this." He sure does -and, as Scout II did not
know, the stereo effect makes it gain even
more in the very some way. A superb "inside
look."
Oh yes-Scout II mentions, in passing, that
"you can almost see the ice floes and churning.
Finlandinn sen." A slight geographical confusion there-he's thinking of Greenland,
which belongs to Denmark, not Finland. But
all's fair in love and musical geography.
-it
Beethoven: Violin Concerto. Fritz Kreisler; London Philharmonic, Barbirolli. (Recorded in 1936).
Angel COLH 11.
For more years than I can remember, this
was THE recording of Beethoven's only violin
concerto. There just weren't any others worth
fussing too long about.
In those days, the usual thought was that
if a piece had been recorded, and well recorded, why bother with a duplication. Too
many 78 -rpm records were involved in such
undertakings to make them feasible, anyhow.
So the repertory on 78 grew up with but one
or two versions of each famous piece, and
these lasted as long as. say, the old front wheel -drive Citroën model, same period, replaced only after a quarter- century or so of
continuous production. So it was with this
ultra- famous recording.
Scout II, being somewhat younger than
myself, was a good bet to try this out on -he
didn't know it from its early days. Again
predictable reaction. "Beautiful," he writes.
"Sensitive, thoughtful, big and open -sounding ;
delicate violin playing." And he notes the fine
sense of continuous flowing melody, which is
the toughest thing to get over in the long
stretches of this concerto.
Only further note I need add is that the
recording will be smooth, lacking in highs
but entirely pleasant in sound (with plenty
of bass)
the acoustics, like most of the
period, will seem rather dead to your ears.
-
;
Berlioz: Symphonie Fantastique. A. Orch.
Nat. de la Radiodiffusion Francaise,
Cluytens.
Angel 35448
Orch. Nat. de la Radiodiffusion Francaise, Beecham.
Capitol -EMI G 7102
Seeing double? Nope-these two are by the
from
the same European
same orchestra,
company, EMI (it includes both Capitol and
B.
(Continued on page 66)
AUDIO
58
2.
Ormandy.
MARCH, 1959
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CHARLES A. ROBERTSON'
STEREOPHONIC
The
Drinkard Singers:
Back Home Choir:
I
A Joyful Noise
RCA Victor LSP1856
Do Believe
RCA Victor LSP1857
Something in the air of northern New Jersey must he quite salubrious for gospel songsters and they flourish there in evergrowing
chorus. Its environs served as a center in the
development of the vital and driving gospel
singing of the present day. Both of these units
rose to prominence in Newark and were sin-
gled out to appear at the Newport Jazz Festival, where they demonstrated the close bond
between the two idioms. The seven members
of the Drinkard Singers are all brothers and
sisters, except .for Judy Guions, an exciting
soloist who 1s the youngest of group. Under
the leadership of Lee Warrick, the eldest sister, they sing their own arrangements of spirituals, some of which go as far back in tradition as Just a Little While to Stay Here, Wade
in the Water, and Ring Those Golden Belli.
Tricky and infectious rhythms shine throughout much of their work, and the deep reverence of their approach is characterized by
Sweet Hour of Prayer, and Use Me, Lord.
The massed voices of the Back Home Choir,
an ensemble of sixty selected mainly from
among the members of the Abyssinian Baptist
Church, incorporate the same righteous qualities. The greater size may make it slightly less
fluid. although this is not apparent certainly
on Roll Jordan Roll, and the vibrant Waiting
For Me. The increased power is well -controlled,
however, and has its own compensations. Also,
the group boasts a number of full -throated
soloists, headed by Carrie Smith and Robert
Ross, whose wife, Janie, is listed among a
cast which includes the Reverend Richard
Baker, Terry Patrick, William Thomas and
Bessie Lewis. They contribute greatly to the
colorful interpretations of Walk in the Sunlight, I Cried Holy, and Coming Home.
Recorded in Webster Hall, the stereo sound
has a spaciousness that is both live and natural. It allows for less congestion than in the
monophonic versions and the soloists are nicely
centered, with the organ well balanced and
spread out in the background. The interplay
between the choral sections is cleanly defined
and the climaxes are free from distortion. A
rewarding effort, in sum, on the part of all
concerned.
Ahmad Jamal, Vol. IV
Argo LP6365
When Ahmad Jamal developed the formula
for his trio, he took into consideration the
setting of an intimate supper club and its
sophisticated patrons. His style is subtle and
departs from the customary practice of keeping the pianist and leader always in the limelight. He realizes the value of silence and
knows when to transfer the melodic line to
Israel Croby's bass, or call on Vermeil Fournier to tattoo a graceful figure on the drums.
Each member is an engrossing soloist and in
combination they operate with a skill that can
`732 The Parkway, Mamaroneck, N. Y.
mesmerize an audience. All these qualities
are more adaptable to stereo than the format
of most trios, as is stunningly brought out by
this first appearance in the medium.
The location is Washington's Spotlite Club,
and engineer Malcolm Chisholm came in from
Chicago for the date. Instead of centering on
the piano, as might appear logical and would
be the procedure in most cases, he focuses on
the bass, placing the piano on the left and the
drums on the right. Whenever one of these
lust instruments is heard in a solo, it fills out
the center and the bass is directly behind. In
this manner the melodic line and a firm, pulsing bent are always predominant, with the
miscellaneous embroidery clearly defined on
either side. This particular setup might not
work on all trios, but Jamal's commercial appeal is bound to result in more pianists adopting his format.
His last recording, made at Chicago's Pershing Lounge, was a bestseller and this one
seems likely to repeat that success. There is a
colorful reading of Lecuona's exotic Taboo,
and a romping Stompin' At The Savoy. His
ballad style is revealed on Autumn In New
York, Secret Love, and Should I. Jamal knows
how to please the customers, but on after hours session might reveal another aspect of
his talent.
Four French Horns
Elektra 234X
Mat Mathews idea of joining his accordion
to four French horns and a rhythm section
has distinct possibilities for stereo. Most of
them are realized in the recording, previously
reviewed in this column in the monophonic
version, particularly in the mellifluous blend
of the ensembles. Separation tends to make
some of the solos sound less full, depending
upon the placement of speakers and the flexibility of your controls. The natural tendency
of the horns is toward a distant, haunting
effect and stereo works to accentuate it. Julius
Watkins and Dave Amram are the featured
players, helped out by Fred Klein and Tony
Miranda.
Pee Wee Erwin: Oh Play That Thing!
United Artists UAS5010
Jelly Roll Morton: King Of New Orleans
RCA Victor LPM1649
Jazz
These days the house bands slip in and out
of Nick's, a Greenwich Village institution
from the time of speakeasies, without benefit
of publicity in the jazz press. One of the best
is headed by Pee Wee Erwin, who held a trumpet chair in the original Benny Goodman band
of 1934 and later joined Tommy Dorsey. High
among his current interests is the work of
Jelly Roll Morton and his search for copies of
the scores led him to the warehouse where
the Melrose publications now repose. Among
those unearthed are Kansas City Stomp,
Georgia Swing, Granite's Spells, and Black
Bottom Stomp. They are affectionately recreated here, along with an arrangement of Morton's reading of The Chant. Ken Davern, an
admirer of Omer Simeon and George Lewis,
aids greatly on clarinet in establishing an
authentic style, and solos engagingly on Big
Pond Rag. Lou McGarrity, on trombone, tills
out the front line.
The fine temper of the recording is spoiled,
unfortunately, by a liner writer who finds it
necessary to refer to the place and its music
as Nicksieland. His cute remarks about what
was played there in the 30's, when Muggsy
Spanier and Sidney Bechet were on the stand,
must be considered in the light of a youthful',
ness which would have denied him admittance.
And he perpetuates the myth that Eddie Condon engaged actively in the proceedings. Anyone who was there knows the nominal leader
was busy furthering the cause of jazz among
customers in Julius' Bar, thereby encouraging
them to go back across the street.
Stereo distributes the horns and engineer
Bill Schwartau achieves an excellent balance
for the five -man rhythm section, which includes a banjo and tuba. The original Morton
versions will never be available in stereo, but
they are now restored to the catalogues in
monophonic form. All the tunes selected by
Erwin are listed and there are eleven others.
some with alternate masters. When reissued
several years ago on the "X" label, the sound
failed to match the early 78's. In this rernastering, Victor improves on the originals and
you might try it on your stereo rig.
Larry Fotine: Take Five
Bel Canto SR1009
Calling his crew the Beale St. Buskers,
Larry Fotine makes no pretensions to playing
anything more than pure dixieland hokum. In
answer to any critic's remark that it might be
suitable for silent movies. he definitely proves
the point on Rink Tink Piano Man, and Old
Time Movies. The balance of the recording
and the placement of the instruments in stereo
are as good as you will find anywhere. It is
ideal for purposes of demonstrating your
equipment at a gathering where other types
of music might seem out of place. It recalls
the days when Clara Bow and Glide Gray were
the life of the party, dancing to the rhythms
of Goodbye Blues, Mama's Gone Goodbye, and
Yee, We Have No Bananas.
MONOPHONIC
Knocky Parker: Old Blues
Audiophile AP60
For a sequel to his ragtime volume of last
year, Knocky Parker is back at the keyboard
of the Boesendorfer at Carroll College for a
program of fully matured blues. The depth
of his research into the subject is shown by
his tributes to several early pianists. Cow
Cow Davenport is represented by Chimes
Blues, and Little Brother Montgomery by
Vicksburg Blues. Complete with the descriptive vocal is Wesley Wallace's No. 29, and
a whole school of playing is recalled on
Boogie Woogie Blues, and Make Me a Pallet
on the Floor. All of these were specialties
of the originators, used to display their
individual styles. Rather than copy recorded
versions with exactitude, Parker transforms
them to conform with his own ideas and
complements, in each case, a work which
belongs in every jazz piano collection.
How many tunes now known mainly in instrumental form were first thought out by an
unknown pianist is a matter for conjecture.
Parker pursues this line of inquiry back to
what he believes might have been the primarily pianistie impulse behind Sister Kate, West
End Blues, and Willie the Weeper. His explorations are consistently interesting and the
traditional standbys are seen in a new light.
Their sentiments are beautifully revealed and
the piano sound is superb.
Tambourines To Glory
Folkways FG 3538
Langston Hughes wrote these songs to help
tell the story of a gospel church in "Tambourines to Glory," the novel and play which
are companion pieces to this recording. The
choir of Harlem's Second Canaan Baptist
Church under Hugh E. Porter, director and a
powerful pianist, is augmented by the composer Jobe Huntley, who alternates as featured soloist with Ernest Cook. Instrumentalists include organist Hampton Carlton,
guitarist Yvonne Cumberbatch, gospel saxophonist Carl McWilliams, and teenage tambourinist Benjamin Snowden. They make a
joyful sound and give substance to the novel-
AUDIO
60
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MARCH, 1959
or
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KE
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VOL. 9
UP THE MISSISSIPPI
Lazily lounge on that of Mississip' steamboat, and let
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deep South included on this, their latest album.
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61
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Ist's expressed opinion that the gospel church
is the last refuge of uninhibited Negro folk
singing. luip rov isatiun n Isu plays its part and
even composed pieces allow for individual
statements or eluibura I inns which must give
the participants a sense of sat isfaet'
similar to that experienced by creative jazz instrumentalists.
For this reason, the performers show no
constraint in the presence of both writer and
composer at the recording sess inn. lurid at the
church and admirably engineered by Dave
Hancock. The words and tunes are serviceable, and the arrangements are built along
lines familiar to the singers. They are completely at ease in the solemn Dome to God,
or the furious rhythms of the title song.
Hughes is much more successful here than in
his recent effort to combine poetry and Jazz.
due to the naturalness of the Porter ensemble.
In his next suoli experiment, he should be impelled to entrust it with sonic of his verse.
Andy Griffith: Shouts the Blues and Old
Timey Songs
Capitol T1105
Back Country Blues
Savoy MG14019
It often happens that a blues singer will
operate under wraps in it concert hall or recording studio, especially just after someone
has informed him of the ethnical value of his
work. Andy Griffith claims the person who introduced him to the blues regretted it, classing him later as "the worst blues singer he
ever beard." If anyone has commented since
on his cultural importance. It served to inhibit
him no mure than the first remark. Ile treats
the blues like an old pair of shoes and they
are Just as comfortable on him. Among the
dozen songs are several recollected from his
birthplace in the mountains of North Carolina, including Little .Maggie, Molly Darlin',
and 7'he Cratrrlad Song.
Besides helping out on guitar, Brownie McGhee sings along on Pick a Bale of Cotton,
and an unidentified harmonica player sounds
remarkably like Sonny Terry. Both of these
performers have been impressed with their
worth as folk artists. When they made the
dozen blues assembled by Savoy, they were
more concerned about tilling Juke -boxes and
making a little money. The result is one of
their most rewarding and unrestrained albums.
By the time a small band Joins in on four
numbers, you will know what the blues are
all about.
Benny Gelions New York Scene
Contemporary C3552
With this album. Contemporary extends its
operations to the hast Coast, having commissioned Jazz critic and philosopher Nat Ilentoff
to supervise n series representative of jazz
happenings In that part of the country. To ensure engineering comparable to the high quality established at the company's California
studios, Dave lia ticuek was engaged to bandle
the sessions and tapes were sent west for mastering. When it was recorded in October. 1957.
Benny Golson had yet to appear as leader on
an LP. Since then the dam has burst and several estimable productions are gaining hie
wider recognit lin. This one presents une of
the broadest views of his many talents, east ing hint as composer, arranger, soloist on tenor
sax with rhythm section, and as leader of n
quintet and nine-piece band.
'l'he Golson compositions are Whisper Not,
Step Lightly, Blues It, and Just Icy Myself,
the first three played in his own arrangements. You're Mine You is chosen to display
his warm, sensitive ballad style. Trumpeter
Art Fermer is the other horn in the quintet,
with Gigi Gryce, Sahib Shibab, Jimmy Cleveland and Julius Watkins added on the three
hand numbers. Gryce contributes Capri, and
arranges Ray Bryant's Something In B Flat.
The recording places Charlie l'ersip's brilliant
drumntin_ in excellent perspective.
Johnny Richards: Experiments In Sound
Capitol T981
For the album which introduces! bis new
orchestra, Johnny Richards used the title
"Wide Range," choosing it as a term descriptive of the massive effects and rich tonal
palette employed in his arrangements. In an-
INTEGRITY IN
AP
other sense
his current
Afro-Cuban
an extract
it would be equally suitable for
effort, a pleasant concoction of
rhythms. ballads, show tunes, and
from an orchestral suite. More
space is devoted to meliudiea that are romantic and plainly danceable. They account for
some of the most successful moments. possibly bemuse both the leader and his sidemen
seem more relaxed than when playing Richards undiluted. Ile should be prevailed upon
to compile an entire set along the lines of his
styling of 9-hat Is There l'o Sag, No .(loon At
All, This 'foie, 111111 I /ow Are Things In
(i been Alorra.
1lesu ite his affection for complex forms,
It iehas-its never stints the soloists and his
writing provides ample room for the likes of
Billy Byers. Iturl Collins, Jim Pahl, Genie
Quill and Frank Soculow in shims their wares.
Recorded at Riverside Plaza. the seventeen
pieces sound with a deep resonant,. that is a
delight to hear.
Art Blakey and the Jazz Messenge:s
Blue Note 4003
Max Roach: Deeds, Not Words
Riverside RLP12 -280
A r,:in cella( ed Jazz Messengers, under the
musical direction of Benny Golson and with
Lee Morgan taking over ou trumpet. produce
their best reeord since Vorace Silver left the
group and set out on his own. By way of celebration. Art Blakey has it new showpiece,
Drum Thunder Suite, born of his desire to
play- a set husking exclusive use of mallets.
Written by Golson in three parts. it combines
several revealing facets of drumming in n
more attractive setting than is usually provided for such forays. Another aspect of this
talent emerges in Blues ilari-li. where a New
Orleans street beat underlines the bugle-call
bene.
Additional con t r ibtrt ions f
Golson are
bouncey Along Came Betty, and Are You
Real? Also a line tenor -sax soli on Come Rain
or Come Shine, and his steadying influence on
a
Morgan whose oho runes, in consequence, are
less flashy and more simple and melodic. The
change in personnel in voi ves a clean sweep
MUSIC...
I
.,=-r
0(
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POWER OUTPUT: SC Rating'
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NOISE LEVEL: 70 db down (Aux.).
1
62
AUDIO
www.americanradiohistory.com
MARCH, 1959
a i".e-_ -,
and Blakey has the support of Bobby Tim mona, a pianist who demonstrates his strength
on an original blues. and bassist Jymie Merritt. That the Messengers are back in form is
a major jazz event and this recording is its
landmark.
Since the departure of Sonny Rollins and
Kenny Dorham, Max Roach has engaged in a
similar talent hunt. Ills new pianoless quintet is composed of younger musicians, and he
seems intent on seasoning them until they fit
his requirements of n new sound and approach
to jazz. Ray Draper, on tuna, and bassist Art
Davis move freely from rhythmic to melodic
lines. Booker Little, trumpet, and George
Coleman, tenor sax. show a continuing development. To satisfy the Roach fans, there is a
substantial unaccompanied drum solo.
Glen Gray: Sounds Of The Great Bands,
Capitol T1067
Vol. 2
The second installment in Glen Gray's review of the foremost recordings by famous
bands of the fairly recent past is better than
the first. The Hollywood studio stalwarts
which constitute the Casa Loma orchestra for
these recreations enter into the spirit of the
assignment with greater zest and even improve
ou some of the originals. Several exceptional
performances are added to the convenience of
having them tied In one neat package with
immensely improved sound. Cappy Lewis, n
Woody Herman alumnus, again plays his
trumpet solo on Blues on Parade. Plas Johnson takes over the Dick Wilson tenor solo on
Motet' Swing. Bunny Berigan's trumpet part
on The Prisoner's Song goes to Shorty Sher ock, and Pete Candoli spells Manny Klein at
being Erskine Hawkins on Tipple' In.
Raymond Scott, a sound fancier before hi -11
was knee-high, should be thrilled by the treatment of Huckleberry Duck, with clarinetist
Gus Bivona in the lead. Other bands revisited
in this chapter are those of Larry Clinton,
Count Basie, Tommy Dorsey, Glen Miller, Jan
Savitt, Charlie Spivak, and Bob Crosby.
,-
.r
.
The Music From Peter Gunn
RCA Victor LPM1956
By television standards an adult mystery adventure series, "Peter Gunn" has probably
introduced as many youngsters to the sounds
of jazz as any of the lavishly produced jazz
shows. The identifying themes and background
music are the work of Henry Mancini, who at
the age of thirty -four has credits on such films
as "The Benny Goodman Story," and "The
Glenn Miller Story." He conducts the same
jazzmen employed on the sound track in an
excellent sampling of the smartly -tailored
writing which characterizes all the programs.
They consist of some of Hollywood's outstanding modernists, although this term is relative
as several made their reputations before the
coaxial cable stretched coast -to-coast.
The attractive opening motif is stated by
drummer Jack Sperling and the walking bass
of Roily Bundock. Ted Nash's alto sax is n
feature of Dreamsville, and Ronnie Lang lends
apt phrases on baritone sax to Sorta Blue.
Other participants are Pete Candoli, Milt
Bernhart, Dick Nash, Johnny Williams and
Larry Bunker. The sound is sleek and chrome
fitted.
Jack Marshall:
1
8th Century Jazz
Capitol T1108
The rococco packaging of this album may
fool you for a moment, but only until bassist
Red Mitchell and drummer Shelly Manne are
detected lurking in the background. Then you
might suspect the presence of a swinging beat,
no matter what period the instrumentation.
Auditioning any track will prove that point
and give a clue as to the chamber group Jack
Marshall imagines he heard two centuries ago.
Apart from certain personal embellishments,
his arrangements conform in style to those
introduced by Chico Hamilton units, and are
just as modern. The similarity extends to the
personnel, with Milt Raskin added on harpsichord to form a sextet.
Marshall plays unamplified guitar and flute.
Flutist Harry Klee doubles on bass flute and
recorder. The cellist is Edgar Lustgarden and
the tunes are a dozen of today's standards. No
Eighteenth Century Drawing Room, and who
will miss it. The present Hamilton outfit had
better look to its laurels. This group can
match it now and if organized on a permanent basis would soon put it in the shade.
The Kingston Trio: From the
Elektra 157
Since turning professional in May, 1957,
for an engagement on the campus of Stanford
University, The Kingston Trio achieved fame
on the folk music circuit before bursting out
with a success of hit parade proportions in
their first album. In a performance recorded
live at San Francisco's fabled "hungry i," they
detail the reasons for their popularity, from
the breezy, informal introductions to the group
participation of When The Saints Go Marching In. All are accomplished guitarists, and
Dave Guard, leader and arranger, doubles
with Bob Shane on guitar, while Nick Reynolds switches to bongos and conga drums to
heighten the pulse of Zombie Jamboree, and
Wimoweh, a Zulu hunting chant. They range
from Gué, Gird, a French 'lullaby, to the Appalachians for Shady Grove, and Lonesome
Traveler. Less familiar is The Merry Minuet,
a cogent comment on the Space Age not likely
to be broadcast by many radio stations. To
enjoy Its wry humor, you must go to the
source.
An equally versatile group is the Folk Singers, each of whose male members is heard taking the lead on one or more of the sixteen
numbers. Erik Darling, along with his country style banjo, is in charge of Poor Howard,
Run Come See, and Pay Me my Money Down.
Dylan Todd singe Hullabaloo, Little Maggie,
and.adds new verses to Deep Blue Sea. Don
Vogel comes to the fore on Peat Bog Soldiers,
a dramatic reminder of the concentration
camp at Dachau. Carol Wilcox completes the
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i"
The Folk Singers: Run Come Hear
NEW "STEREO 60" AMPLIFIER
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A
"hungry
Capitol T1107
GD
:10:
63
MARCH, 1959
www.americanradiohistory.com
quartet and odds her voice to suell Joint efforts as Ity'm By, Keep Your Hand on That
Plow. and Michael. Boa- the Boat Ashore.
Both groups ably fulfil the basic requirements
of folk music--that of communicating with
an
n
ndienec.
South Seas Adventure
Audio Fidelity AFLP1899
Na Mele O Hawaii
them with the ubservat lion that "the distinctive qualities in his music were often startling
accents and dynamics .
. when it cause to
publishing his marches Mr. Sousa not only
hp out as many of those unique effects as he
possibly could, hut lie often threw n few red
herrings in there for good measure." He uses
a It Vol ii hand to restore the accents, as he recalls them, and expands the dynamics to the
limits of modern recording techniques. With
lu power of forty -odd bandsmen at his command, lie affords stirring performances of such
rousers as Washington Post, Liberty Bell,
and Manhattan Beach. Also revived is his
personal favorite, The Free Lance.
As an introduction to his own Freedom
Song, he assembles a medley of ten marches
linked with struggles for freed
in various
parts of the world, including Colonel Bogy,
Marching to Pretoria, and Scotland the Bra re.
A work dedicated to the cause of international
goodwill, the word freedom is pronounced in
forty -four different languages during its
course. A warranty that it is sounded each
time in true native style collies from the composer.
I
Capitol T1092
The current Cinerama opus is a re ap lem'eo!
travelogue Of a Voyage across the South Pacific to Australia, complete with stopovers at
Various enticing islands. The weuud track is a
montage of Alex Forth's richly descriptive
Nei ore and the realism of native spectacles
reco ruled on 'ovation. Both are transferred to
the recording. and the traditional strains of
Aloha Oc echo across the water as the ship
reaches Hawaii. Polynesian maidens engage
ill a do tieing contest in Tahiti. while the
young men test their skill at coconut spear ing. At Tonga. four hundred school girls demonstrate the effect of niissuinar teaching on
their rhornl singing and a church group sings
a translation of Onward Christian Soldiers.
Visits are made to the Fiji Islam's. New
Hebrides and New Zealand. The finale comes
at the festivities of n picnic in the outback
country of Australia. The composer a lucís
an orchestra of ninety -seven pieces and Cineranut employs its best recording techniques.
A stereo version is available.
For those desiring a longer stay in Hawaii.
the Wesley Edwards production for C'apitul
features the Kamehameha Alumni Glee Club.
The twenty -four volees of the mixed chorus
are heard in the rare harmonies of fifteen
native songs. 'There is the inevitable Aloha 0e,
uunpled with Sung Of The Islands, but the
others are less familiar.
Meredith Willson: Marching Band
Capitol T1110
The basis of Meredith Villson's recreation
of six Sousa marches is the three seasons he
played under the March King. commencing nt
the tender age of eighteen. and he prefaces
Mexico: Its Sounds and People
Capitol T10185
F. Moreno Torroba: Plays Agustin Lara
Seeco SCLP9149
'l'he latest entry in Capitol's --mi,s of "international sounds" Is as colorful as the
umsaic- patterned facade of the l nirersity of
Mexico Library tin the rover. t_'u rlus t 11 stet,
vacationing manager of Nut "King" Cole, acts
as guide and visits a fo..t hall game, bullfight,
an Independence Day celebration, and spends
it Sunday with the vaqueros at the Rancho
Del Charm. Itiminiu Rodriguez. a cluunpion
ruse driver at sixteen, wheels his Porsche before the micron'
's and children play games
or struggle with English in n classroom. Engineers Juan ('u, nupo and Eduardo Baptista
tie the sequences together w'illi bits front a
street organ, marimbas, a uuariachi band, and
an assortment of street noises, including
reailist it church bells. Tourists bargain with a
bracelet peddler. show faint heart at climbing
the Pyramids, and Journey to a movie set.
Border towns and customs guards, the most
painful part of their trip, are thoughtfully
omitted.
The popular compositions of Mexico's Agustin Lare potlachs an international flavor and
Pou Belong To .4fg Heart, Be .Vine Tonight,
and Granada are favorites in this country.
They are listed among the dozen melodies recorded in Spain by Frederico Moreno Torroba.
who arranged them for u large orchestra in
the Kustelanet-Z niold.
Bud Shank: I'll Take Romance
World Pacific WP1251
Joe Bushkin: Blue Angels
Capitol T1094
These two meetings of jazz soloists
and
strings, gratifying for the richness of sympathetic backgrounds, are most productive of
lyric swing. During a European tour last
spring, Bud Shank recorded in Milano with
an ample orchestra led by Len Mercer. who
collaborated with Giulio Lilian° on the
arrangements under the name of Ezlo Leoni.
Said to be the first combined studio effort in
modern Jazz by musicians of the twu countries, it finds the Italians on their mettle
they ended by cheering: their guest's
performance. Shank alternates on flute thud
alto sax with eustennary lucidity on These
Foolish Things, Someone to Watch O rcr Me,
the title tune and eight others.
Aviation enthusiast ,foe Itushkin dedicates
a dozen macs, each containing the word biotin the title, to the Flight Demonstration
Team of the l'SN, shown streaking across the
cover in new Grumman FIIF-1 Tigers. His
piano sanding ranges from the bright colors
of Mat' Roma. lilt Blue Ilearen, and Beyond
the Blue /Inri :on to the darker hues of Mar
and Sentimental. and his original Blue Angel
Blues. The third album in Ilia association
with arranger anti conductor Kenyon Hopkins. it swings more vigorously than its
moody forerunners, sounding like Bushkin of
the 40's. Two sections of four trombones each,
six violas. four cellos. and two dntauors
indicate a
o version is in the offing.
J£
and
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AUDIO
64
www.americanradiohistory.com
MARCH, 1959
.
.
ut
-
^
.a
AUDIO ETC
(front page 16)
is good. As old readers know, this has al-
ways been
"hi-fi."
my
philosophy
concerning
Setting Up
You now have the basic material to
anticipate my own variety of stereo
projection set -up. I threw out my first
screen, normal room size, and got me a
50" x 50 ", the largest I could dig up in
regular stocks. I would prefer something
at least six feet by six, but haven't the
loose cash to sink into one.
Take the longest possible throw you can
find, between screen and projector, in your
home- usually a diagonal, possibly involving a hallway. Put the projector back,
the screen forward, and a bit high. Fill
the screen full -size, even slightly larger,
cropping off a few minor details around
the edges. (You can lift the projector
occasionally, if need he.) It won't matter
if the viewers in front have to look uphill
a bit.
Your chairs should, as always, be clustered around the center line (mount the
projector high, too, to send the beam over
the taller heads) BUT, put everybody up
forward. Concentrate the entire audience
well in front of the projector. Put the
majority, if you can, near or beyond the
point where the size ratio is 1:1 -which
means practically at the screen. Resist
people's natural tendency to sit around the
baek and sides of the room. They'll get that
six -inch window effect and the distorted
depth. Put all the kids on the floor, practically at the foot of the screen. They'll
love it. Beep the picture BIG, for each and
every member of your audience.
Except, of course, yourself. You have to
he back at the projector, and you'll have
a job trying to focus and blend the pair
of pictures at this disadvantageous distance. Try to stand in front of the projector and reach back towards it. Not easy!
Leave a space so you can walk forward a
few feet to view the effect at a better
nearness.
And there you have it. I won't impose
on our audio friends much further except
to suggest a couple of adjustments that
are vital. The projector has, in addition to
a joint focus knob (like a ganged stereo
volume control in "our" stereo), a separation control, spreading the two pictures
sidewise, and an up- and-down adjustment,
to register the inevitable misfits, where
one picture conies on the screen higher than
the other. It takes a lot of knack to operate
these quickly and surely. And the focus
must be adjusted constantly, too , for
accurate detail in the relatively enormous
enlargement you are producing for your
viewers -much greater than with "flat"
screen projection. Three knobs, all to be
juggled at once.
In showing pictures (you will have
checked them over ahead of time, if you
are a better man than I), start with the
up- and-down alignment. That hurts most
when it is out. As the picture appears,
quickly move the up -and-down knob until
some visible point in both pictures is level
a mountain top or the peak of a
house roof, or a human head. Look over the
top of your glasses, so you can see both
images. This is the absolute first necessity
-and virtually every picture will need
adjustment. The two pictures overlap
dizzily -but they must be on a level with
each other.
Second, quickly adjust focus, if needed.
Many films tend to "pop" with the sudden
heat and must be re- focussed, a problem
common in all projection.
Third, SLOWLY adjust the sidewise
separation of the picture for optimum
effect. And thereby hangs my final pointer.
-say
Push -pull Perspective
In the pair of stereo pictures no two
points are precisely the same. Join together
a post in the foreground so the two pictures coincide on the screen, and the
mountains in the background will be separated a couple of inches in the actual
images. Join the mountains (infinity) and
the posts will stand apart, as you look
without glasses. These differences, of
course, constitute the stereo element itself,
the depth -producing effect, and they correspond very closely to the differences in
phase between Channel A and Channel B
in our stereo sound signals. They can't all
be in phase at once -or the two photos
would be identical, as would our two sound
channels. A striking and interesting parallel here, to think about.
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a
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GD
:.:
65
www.americanradiohistory.com
There is even "phase reversal" in stereo
photography. If you mount your picture
wrongly left to right-"reverse the speakers" -you will get inverted depth. Trees
are at the back of deep slots in the sky,
which is in the foreground. Mountains
are cardboard cut -outs standing in front
of the clouds above them. (Black -andwhite, or shadow perspective remains
normal, of course, and the two types fight
each other. Same is true of stereo sound in
reversed phase. Some effects are more or
less normal; others are reversed, inside
out.)
How (to return) do you know which
parts of the overlapping images on the
stereo screen to make coincide? Should the
background match, the two pictures actually hitting the same spot on the screen?
Or foreground objects? You have a very
wide range of choice, via the separation
control. (It moves the lenses.) And you
have a fairly wide range of choice in the
viewing itself. The eye is remarkably
adaptable.
Think of it in this simple way. You are
looking through your screen, into depth
you may even look in front of it, at a
virtual image in the air. The screen itself
-
is merely an accidental point, the frame of
the window, the window glass.
The point at which your two imagea
coincide is always seen at the screen. Other
points are in front or in back, according to
their natural separation.
Therefore, if you wish your infinity to
be where it belongs- through and beyond
the screen -you must make some of the
nearer points coincide. With projection's
exaggerated sort of perspective, some
nearby points may be too close for the eyes
to join -you have to push them back a bit.
As you turn the separation adjustment
(sliding the overlapping pictures together
or apart by about a foot or more in normal
viewing) the screen -point, in the viewed
picture, is nearer or further. Bring them
closer together (looking at them outside of
your stereo glasses) and you move the entire picture forward. You can put your
mountains right at the screen if you want,
the rest floating in front of them, sort of
miniature; but don't do it.
The best technique for average pictures
is to choose a nearby object, perhaps eight
or ten feet away from the camera, and join
its two images so they coincide on the
screen. Then all the rest of the picture will
fall into place, most of it behind the
screen, with infinity in its proper distant
location. The eves can take a certain
amount of nearer foreground in front of
the screen without noticing it.
If, however, there are violent contrasts,
close -up
with some objects very near
leafy branch, a person's arm -you must
push the whole picture further back, or the
exaggeration will be too much for the eyes
and the pictures won't join. Wider separation. Same with close -up pictures of people, minus distant background: push them
back behind the screen, via wider separation.
You'll quickly find that in most ordinary
outdoor pictures you can take a quick look
(outside your glasses) at the background,
spread its points apart about two or three
inches, and infinity will be where it belongs,
the rest in place. But you must be ready
for quick adjustments.
And if your two loudspeakers seem to
spread that string quartet out into a
twenty -foot line of players five feet apart,
if the stereo Steinway sounds as if the
keyboard were forty feet wide, then slide
your two speakers closer togeth- hey! I've
slipped into the wrong kind of stereo.
From here on, we'd better keep them
well separated.
Æ
-a
RECORD REVUE
I
Angel) and both are non -stereo versions.
Which only makes us wonder the more why
there are now three U. S. labels in this combine- Angel, Capitol and Capitol -EMI. Maybe
It's the old Ford -Edsel -Mercury overlapping
competition, or GE-Hotpoint, deliberately applied to recordings? Who knows?
Anyway, Scout II took over these, while I
managed a third version from France (Omega
from page 58)
stereo) in an earlier issue and Scout I took
over still a fourth version, as reviewed above.
You gotta have a team, these days, to keep
afloat.
Well, darn it, here we go -Scout II finds
both these versions extraordinarily good,
though remarkably different. What can you
do but go out and buy 'em both. Ile says that
the Beecham version is "superbly intelligent"
(he's running out of adjectives) ; the orchestra Is exquisite, the climaxes powerful, perfectly timed. the whole thing both passionate
and yet completely controlled. This, of course,
is Beecham all over. He is an outstanding
stickler for fantastic accuracy of detail, for
exact phrasing and ensemble, beyond any
other living conductor; he can even take his
music slower than others, simply in order to
MUSIC...
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AUDIO
66
www.americanradiohistory.com
MARCH, 1959
get over the inner details that he insists upon
which might he lost in the excitement of a
more impetuous performance. Yet Beecham
is not ever less than exciting, even when he is
obstinate and annoying, as occasionally in
some of his Mozart and Haydn.
The best thing about Beecham's work is
that he hires native musicians and knows
what to do with them -hence the heauty of
this all- French performance under his leadership. That's what Scout II hears.
The Angel recording, saine orchestra hut
under a leading younger French conductor, is
"more modern," Scout II says, more taut,
more rhythmic, seems to be "held together by
electric wires -it's sharp, explosive and very
exciting." Also, however, it is less Romantic
in feeling than Beecham's, less large, less
sympathetic. But, he says, this puts forth
another aspect of the big piece, and it is not
a bit less worthy than Beecham's. Very fine
recorded sound in both of these, by the way.
So -crank up your dollar budget and go out
and buy both. The contrast should be well
worth it.
Strauss: Don Quixote. Phila. Orch., Or-
mandy.
Columbia ML 5292
I know -this and both the two Fantastic
Symphonies reported on by Scout II were on
our recommended list last December. But
since Scout II did play them, we might as
well mention them again. The recommendations, you see, turned out to be well founded.
You can put this alongside of the Sibelius
Second Symphony as another surprisingly
lively and expert version of an old war horse
from the versatile Philadelphia -Ormandy
combo. Scout II finds this "full- blown, gorgeous- sounding, good humored, sympathetic,"
the garish aspects of the score tactfully kept
down, the gimmicky parts never getting the
best of the total effect. He's probably thinking
of the sheep- bleating episode, the wind machine and other musical gadget -mongering
that seemed dreadfully modern back in the
a Haydn pioneer and I still enjoy his pre -war
78 records, which introduced me to this very
1890's but which don't really cut much ice
now.
wonderful composer.
Thus, here you'll find the quintessence of
Ieecham's long Haydn experience. in collected
form, three records in this album and more to
come. The music, as always, will he meticulously, beautifully tailored, impeccably played.
It will be somewhat reserved and classic in
sound, emphasizing the perfect proportion and
structure that is so very much a part of
Haydn.
"Dignified
no stem void drang," says
Scout II. "But this is no loss -these symphonies are performed with depth and self -restraint -but they are never strait-laced or
dull the orchestra is lovely, the music sounds
intelligent (Scout II's highest praise), sharp
and full, because the symphonies themselves
are so magnificent."
Just about what I would expect.
"Don Quixote" can be terribly long and
horribly dull in a less- than -imaginative performance; Ormandy is the man to keep it
alive, shape it for today's listening. I suppose
this is available in stereo too, or will be; my
copy was mono.
Haydn: The Salomon Symphonies, Vol. 1
(Symphonies #93-4-98). Royal Philharmonic, Beecham.
Capitol -EMI GCR 7127 (3)
This Is the sort of album that I could enjoy
listening to over a period of weeks nt a time,
with nothing else to bother me. It was painful
to have to turn it over, lock stock and barrel,
to Scout II -who loves the stuff as much as I
do. But I could tell you ahead of time exactly
what is in the recording, and he has merely
confirmed it for me.
The Haydn symphonies are now well known
mainly in two great series-that is. the late
Haydn symphonies are those in the eighties
and nineties and on up to #104. One series is
that on Westminster with the German conductor Scherchen, his finest work to date.
Scherchen for the first time, in our day,
brought out the remarkably Romantic latencies in these great works, the Beethoven aspect of them. Formerly, they were treated as
"classic" works entirely, on the pig -tailed and
uniformed side out of the Eighteenth Century.
treScherchen rendered them -and us
mendous service, placing these symphonies in
a much truer and more meaningful light in
the present -day scene. The Scherchen success
with the Westminster series reflects this
along with the famous "0," which was only
part of the story.
Beecham is the other (and older) great
Interpreter of Haydn, reflecting the point of
view of an earlier day when Haydn Symphonies were scarcely heard at all-or if any,
then always the "Surprise" or maybe the
"Farewell," complete with red -coated musicians blowing out the candles on their quaint
music stands, one by one. Beecham was thus
.
;
Mahler: Das Lied von der Erde (Song of
the Earth). Grace Hoffman, Helmut Mel-
-a
chert, Symphony Orch. Southwest German Radio, Baden -Baden, Rosbaud.
StereoVox ST-PL 10.912 (2)
This is the collection of songs for tenor,
contralto and orchestra that was the famous
subject of an enormous pre -war 78 -rpm album,
weighing a ton and a pioneer recorded monument. Now, recordings of it are relatively
frequent.
Mahler may he big but lie is always subtle
and wonderfully delicate in detail. Scout II
doesn't think much of this version. It is large,
noisy, exciting, lacking totally in the delicate,
fairy -tale quality of the music. No subtlety,
no poetry, just much "Sturm and drang"Iots of beefy tearing-of -hair. The singers, he
says, are "OK but not special."
There's no beef from Scout II concerning
the recorded sound, which to a good sign
since some of Vox's stereo discs at the beginning were under par in clarity. This one is
evidently of the later and much improved
vintage.
JE
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pre -amplifier
NUMBER OF TUBES: 4.
U. L. APPROVED
DIMENSIONS: 1034" wide, 914" deep,
PRICE: $99.95
(Audiophile Net, Zone
1).
STROMBERG
- CARLSON
DIVISION
GENERAL DYNAMICS CORPORATION
OF
A
Your best single
N. GOODMAN STREET
ROCHESTER 3, N. V.
s.c
y§
MARCH, 1959
RF-
480
''SI,al,ne
-
8" transducer
67
www.americanradiohistory.com
DESIGN OF WIDE RANGE SPEAKER SYSTEM
from page 26)
at usual listening levels. It is retrogressive to tolerate unnecessary distortion
in a speaker system when care and pains
are taken to keep it out of the amplitier, cartridge, and records. To get
enough output with direct radiating
domes to match the low -frequency
driver a great amount of magnet and
iron structure must be used. All these
problems can be overcome simply by the
use of proper loading structures and
horns. The high -frequency drivers in the
Regal system employ the `onophase
throat design and ex ha ust iute diffraction horns.
Power Requirements
Many ultra- compact systems have an
38 db.
Conventional size enclosures using medium efficiency drivers have a sensitivity
rating of about 50 db. This means that
these compact systems must be 12 db
less efficient than medium efficiency systems. To produce a given sound level
these compact systems require 16 times
the amplifier power. it is generally accepted that 20 watts is a minimum requirement for sufficient rnnnl levels and
MA sensitivity rating of about
dytiaulic range with systems having EIA
sensitivity ratings of 50 db. By this
criterion a system which requires 16
times this power would need a 320 -watt
amplifier. This is a horrendous power
requirement. Such an amplifier is not
available for home use.
Most manufacturers of ultra- compact
speakers recommend a 50 to 70 watt
power amplifier. A 70 -watt amplifier
eapacity is the highest that can be obtained within reasonable economy of
size and cost.
Also the 12 -inch ultra -compact loudspeaker cannot safely handle an amplifier of larger output than 70 watts
beeause of heat dissipation requirements
in the Voice -coil area.
The Regal system is three times as
efficient as most of the ultra -compact
loudspeakers. Therefore, it requires one third the amplifier power to produce
the same acoustic output. For the Regal,
then. a 20 -watt amplifier rating will
suffice to produce the same output as
lower efficiency systems requiring 50 to
70 watts.
Conclusion
An effort has been clade in this
arti-
cle to dispel misconceptions regarding
ultra -compact speaker systems.
It has been shown that in order to
obtain flat bass response the efficiency of
ultra- compact speakers must be reduced.
However, if the efficiency is reduced excessively, impossible power -amplifier requirements or excessively compressed
dynamic range results. A happy compromise between loss of efficiency and
flat bass response must be niet.
It has also been shown that conventional 12 -inch drivers in 11/2 cubic
foot cabinets will not produce flat bass
response because of an inordinately
high primary resonance. It has been
proved that removal of the driver suspension stiffness cannot sufficiently reduce the primary resonance to effect
a flat bass response. Some mass must
be added to the moving system to produce the desired results. It is this mass
addition which reduces the loudspeaker
efficiency.
It has been found that the addition
of class to the moving system is not
necessarily just a simple matter of utilizing a heavier thicker cone. A precise
way of adding mass while maintaining
RS -461
Acoustical Labyrinth
Speaker System:
AUDIO
68
www.americanradiohistory.com
MARCH, 1959
.>
flattest possible frequency response is
through the use of a machined metal
ring of exact weight located at or very
near the voice coil.
Misconceptions concerning the inherent linearity and consequent freedom
from distortion of air springs has been
dissolved. Attention has been called to
any elementary physics text to find
formal proof that the adiabatic air
compression and rarefaction is inherently non -linear. Distortion produced by
this non-linearity must be greater in
ultra-compact sealed cabinets than in
larger systems. Too, there is a practical
limit of % -in. to the excursion for 12inch drivers with 11/2 cubic foot sealed
back cavities no matter how linear the
voice-coil structure and mechanical suspension is. Under these conditions a
voice -coil overhang in excess of 3 /16 -in.
is a flagrant waste of precious efficiency.
It has been proved that workmanlike
cabinet joinery will sufficiently seal the
back cavity. Minute air leaks detectable
only with a stethoscope cannot have an
effect on the performance.
High damping factor is an imperative
in ultra- compact systems and the insertion of series resistances not only
negates the high damping factor of a
quality amplifier with resultant deg-
H
response, but
wastes precious amplifier power.
The absolute necessity for good high frequency dispersion, even more important for stereo than monophonic, has
been made clear. Diffraction horn units
provide optimum distribution of sound
into the listening area. These diffraction
horns maintain smooth frequency response and the low distortion that can
be obtained only with horn -loaded high frequency drivers.
The ultra-compact system which embodies the features described in this
article as well as optimized bass range
performance is the Electro -Voice Regal.
The photographs are of the Regal III
three-way system. A Regal IA two -way
system is also manufactured.
In the Regal III both the treble and
high -frequency drivers are equipped
with Sonophase loading assemblies for
flat response, and diffraction horns for
dispersion suitable for stereo. Behind
the hinged front panel are located the
continuously variable level pads which
control the balance of these treble and
high frequency units. Front location
of these controls eliminates the necessity for removal of the cabinet from a
bookshelf location for access to the
back panel where such controls are
often located.
radation of transient
The Regal is fully finished on all four
sides to accommodate vertical or horizontal placement. The exterior appearance of this cabinet is designed to blend
well with all decors. It is available in
beautiful walnut, mahogany or limed
oak.
It would appear that the Regals are
optimumly designed, with consideration
given to all factors, to deliver in an
ultra- compact enclosure the maximum in
frequency response range, efficiency.
and freedom from distortion. Those who
participated in its development look
back with satisfaction on what is called,
in laboratory circles, a "happy" design.
Measuring Equipment
The following laboratory equipment was
used for the measurements covered in this
article:
Hewlett Packard Distortion Analyzer,
Model 330B
Electro -Voice power amplifier,
Model 6006
Translator,
Electro -Voice Logarithmic
Model 6700
Ballantine a.c. Voltmeter
Electro -Voice Laboratory Standard Microphone and Preamp, Model 6100 (Calibrated 10 cps to 100,000 cps)
General Radio Beat -Frequency Oscillator,
Type 1304 -B
D'Arsonval- movement rectilinear recorder.
Æ
100 -watt
STEREOPHONIC AMPLIFIER and
ACOUSTICAL LABYRINTH SPEAKER
SYSTEMS BY STROMBERG -CARLSON
Your best single
source of matched
components for
complete systems Stromberg- Carlson
-4a
Just as the name Yul Brynner stands for integrity in dramatic art, the name
Stromberg-Carlson means integrity in the art of music reproduction.
In stereo, for example: the Stromberg- Carlson ASR -433 dual- channel amplifier
"Stereo Tone Balance" Signal gives you the best musical reproduction.
And to match this perfection, we offer a pair of RS -461 stereo speaker systems.
Each contains one Stromberg- Carlson wide range speaker, one tweeter and a
-with
crossover network, mounted in our exclusive "Acoustical Labyrinth" enclosure.
This enclosure is an effective damping and loading device designed for optimum
performance at all levels.
Judge the musical integrity of these superb music systems for yourself. You'll
find your Stromberg-Carlson dealer listed on the Yellow Pages.
RF -480
8" wide ronge transducer
RT -476
21/4"
PR -488
system: 40-18,000 cps
Cabinet size: 24y," high,
tweeter
19" wide, 10" deep
Mahogany, walnut or limed oak
Crossover network
Effective frequency range of
Ra -416
-CARLSON
STROMBERG
DIVISION
GENERAL DYNAMICS CORPORATION
A
OF
1418C N. GOODMAN STREET
AUDIO
"Auto- speed" clanger
ROCHESTER 3. N. Y.
MARCH, 1959
Acoustical Labyrinth
enclosure
GD
.'
69
www.americanradiohistory.com
NEW PRODUCTS
Morelco Stereo Recorder. Engineered and
manufactured by Philips of the Netherlands, the Norelco stereo "Continental"
tape recorder features push-button controls for ease of operation, twin track recording for economy, and three speeds
7%, 3% and 1% ips. At each of its three
speeds the stereo Continental compares favorably in performance with many machines operating at the next higher speed.
This is due primarily to the Philips magnetic head with a gap of only 0.0002 in.,
which ms §es possible extended high-fre-
-
The mounting arm may be tilted and rotated a full 360 deg. around the base, and
may be extended to a length of 39 inches
from its retracted length of 25 inches. The
reflector may be tilted and swivelled in
both vertical and horizontal planes. Mann-
and attenuation of the upper frequencies.
Made in England by the manufacturers of
Ferrograph tape recorders, the de -fluxer
is distributed exclusively in the U. S. by
the Ercona Corp (Electronic Division), 16
W. 46th St., New York 36, N. Y.
0-5
Heathkit Chatrside Enclosure. In addition to providing convenience and utility
this Heathkit equipment cabinet will enhance the appearance of any living room
with its striking design in either traditional or contemporary models. Designed
for maximum flexibility and compactness,
the enclosure is intended to house the
Heathkit Models BC-1A and FM -3A AM
and FM tuners and the WA -P2 preamplifier
factured in a number of models, the Trombolite is available for mounting on desk,
work bench, wall, machine, or drafting
board. Tech -Lite, 635 Fifth Ave., New York
17, N. Y.
C -3
Irish "Continental" series Magnetic
quency response even at lower speeds. The
machine can be used to record monophonic
tapes, and to play back monophonic or
stereo tapes. The unit consists of a tape
drive mechanism, two preamplifiers with
Controls, one power amplifier, and a wide range speaker. For stereo playback, a second power amplifier and a wide -range dual cone speaker in a matching cabinet is
available as an accessory. Frequency response at 744 ips is 40 to 16,000 cps and
wow and flutter are 0.15 per cent. Signal to -noise ratio 1s 54 db. For further Information write North American Philips Company, Inc., High Fidelity Products Division, 230 Duffy Ave., Hicksville, N. Y. 0-1
Earmaa-Eardon Multiplex Tuner. Designed as a completely integrated multiplex receiver, the Model T250 is an AMFM tuner which may be converted to multiplex by means of the Harman -Kardon
Type MA250 multiplex adapter which plugs
directly into the tuner chassis. With the
MA250 installed, the tuner becomes a one piece instrument providing single -channel
plus compatible- multiplex- stereo reception.
The FM front end is a new shaded -grid
kI
_®
a
,
.;a
-
4117
Tape. Intended primarily for use on a
number of European recorders which are
being imported into this country and
which do not accept a 7 -in. reel, the Irish
brand "Continental" series offers a 5% -in.
reel with extended lengths of tape, and
as well as most any standard record
changer. Adequate space is provided at the
rear for enclosing any of the Heathkit
power amplifiers designed to operate with
the WA-P2. Although intended originally
for these components, the cabinet is not
frozen to specific locations for each one.
Component location can easily be worked
out for the existing situation in each home.
All parts are pre -cut and pre -drilled for
easy assembly. For further information
write Heath Company, Benton Harbor 25,
Mich.
O -6
Goodman Stereo Speaker. The Stereo sfere is specifically designed as a second
speaker in a stereophonic music system.
It operates on the principle that the human ear cannot detect the accurate position of the source of sound at frequencies
below 300 cps. Bass sound, in a system
utilizing the Stereosfere, is channeled to
the existing full-range speaker, with all
correspondingly increased playing time.
Tape lengths range from 850 ft. for standard thickness tape to 1650 feet for double play. Tape recordists who have had difficulty in finding proper reel sizes and tape
lengths for their European recorders may
write ORRadio Industries, Inc., Shamrock
Circle, Opelika, Ala., for the names of
dealers that stock the Continental series.
O -4
tetrode which combines the low noise characteristics of a triode with the sensitivity
of a pentode. The T250 incorporates the
new Harman -Kardon "Gated-Beam" limiter with zero -time -constant grid circuit
and wide-band Foster -Seeley discriminators. A new electronic tuning bar, which
functions on both FM and AM, is framed
in the body of the tuner's handsome
brushed -copper escutcheon. Catalog sheets
containing complete information on the
T250 will be mailed upon request to Harman-Kardon, 525 Main St., Westbury, N. Y.
Tape Head De-Magnetizer. Known as the
Wearite "De- fiuxer," this device removes
residual magnetism from the tape head of
any recorder /reproducer. Simple to use
O -2
"Trombolite" Work Lamp. Although not
an audio item per se, the Trombolite will
find favor with both professional audio en-
gineers and do -it- yourself hobbyists for
the ease it brings to electronic assembly
and kit building. The light source of the
unit is an incandescent lamp surrounded
by a fluorescent tube, either of which, or a
combination of both, may be switched on
to obtain the tonal quality of light desired.
without removing the head screening
shield, it insures maximum signal /noise
ratio, at the same time protecting recorded
tapes from cumulative background noise
sound above 100 cps divided equally between the existing speaker and the Stereo sfere. The Stereosfere delivers clean response from 60.0 to 20,000 cps. Functional
in design and appearance, the unit measures only ten inches in its largest dimension. It can be tilted, swivelled, rotated,
hung from the ceiling or wall, or placed
at normal height. Manufactured in England by Goodmans, Ltd., the Steneosfere
is distributed in the U. S. by Rockbar Corporation, Mamaroneck, N. Y.
43-7
AUDIO
70
www.americanradiohistory.com
MARCH, 1959
"THE INNER CIRCLE Of HIGH FIDELITY"
No matter how much you know about high fidelity, the only way you can hope to enjoy the inside information
that the manufacturers and professionals in the field have, is this:
BE A SUBSCRIBER TO THE INSTITUTE OF HIGH FIDELITY!
Because, as a subscriber to the national association
of the high fidelity industry, you then become a mem-
ber of the "inner circle "... with unlimited access to
answers to your problems relating to high fidelity!
HERE'S WHAT ELSE YOU GET WITH YOUR MEMBERSHIP!
A Test Recording -tape or LP record
-
ALL
THIS
-
to test the fidelity of your equipment to determine proper operation
so that you can adjust it if necessary
value $9B5
...
The INSTITUTE'S Confidential News Letter
-one year's subscription (12 issues) value
(more than
$1200
...
A 6 -month subscription to any one of the following magazines
$30 value)
AUDIO HI FI MUSIC & REVIEW RADIO -ELECTRONICS
HIGH FIDELITY
RADIO -TELEVISION NEWS ... value to $600
A Copy of "High Fidelity Simplified"
:.. value
FOR
$300
Free admission to all High Fidelity Shows
sponsored by INSTITUTE
ONLY
OF HIGH FIDELITY MANUFACTURERS, INC.
$10
Plus membership lapel pin, gold membership card, certificate suitable for framing
I-
And as we said, guidance from the top men of the industry!
Nowhere else can you get the information you will get from the INSTITUTE .
and you can get it only because the
INSTITUTE OF HIGH FIDELITY is a non-
profit organization dedicated to the
betterment of the high fidelity industry,
and greater audiophile satisfaction.
So send the coupon now. Enroll in
the INSTITUTE and enjoy its vast
advantages in making your high
fidelity more enjoyable and more
profitable.
AUDIO
MIII
-
SEND THIS COUPON NOW
IINSTITUTE OF HIGH FIDELITY
\
I
NM NM
National Ilendquarters, Dept.
25 East 23rd St., New York Ia. N. Y.
I
1
II
I
IPlease enroll me as a subscriber to the Institute.
I understand that I will be entitled to all the products, privileges and services
described in this invitation. Meanwhile, please send me The Test Recording as marked
Test Tape ME 473
Test Record 111F 473
Enroll my sir -month subscription for (check one)
AUDIO
HI Fi
A
HIGH
MUSIC REVIEW
FIDELITY
I
,
,
RADIO -TELEVISION NEWS -RADIO- ELECTRONICS
Enclosed is my check or money order for j10 Annual Dues so that my benefit. will
Ibegin immedigtely.,
.
II
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NAM
IADDRESS
ZONE
CITY
NI NM
IMMIMII
MARCH, 1959
STAT[
1=== 111111111M
71
www.americanradiohistory.com
Erie AEI-PEI Tuner. Long known as a
principal manufacturer of component
parts, notably quality resistors, Erie Resistor Corporation, Erie, Pa., has entered
the high fidelity field with a new AM-FM
tuner. Designated Model EM- 085 -ER, the
tuner features an etched wiring board, and
includes in its circuitry two 1.f. stages, a
Announcing
G. A. Briggs'
LOUDSPEAKERS
completely revised
and enlarged in its fifth edition
Written as only G. A. Briggs can ... the pages
are enlivened with touches of warmth, humor,
and simplicity which have sparked the
popularity of all books by G. A. Briggs.
Previous editions of "Loudspeakers" were
instantaneous sellouts ... this fascinating book
has been reprinted fifteen times!
31 engrossing chapters ... ranging from the
development of loudspeakers through room
acoustics, and the modern miracle of Stereo ...
cover all aspects of the design and performance
of loudspeakers and enc osures.
limiter stage, and a Foster -Seeley discriminator. A 300 -ohm balanced input, with trifilar matching coil, eliminates the usual
dual input stage, according to company engineers. Other features of the tuner are
exceptionally low noise level and strong
a.f.c. control voltage. The unit is housed
in a tastefully finished black cabinet with
gold trim.
C -8
Input Transformers. These cased plug -in
input transformers are intended for replacement or original equipment use on
many amplifiers and tape recorders, such
as the Ampex and RCA. They are designed
to match the impedance of microphone,
pickup cartridge or line to that of a high-
1)101)1221M
By G.
Briggs
$450
Mr. Briggs is known to a host of loyal
friends as the designer and manufacturer
of Wharfedale Loudspeakers and as
336 Pages
England's pre- eminent authority on
high -fidelity sound reproduction. 230 Illustrations
At your high -fidelity dealer or bookstore, or write to:
BRITISH INDUSTRIES CORPORATION
Dept. WB49 Port Washington, N. Y.
CIRCLE 72A
impedance input amplifier. All units are
double Mumetal shielded to provide optimum signal -to -noise ratio. Frequency response is 20 to 20,000 cps ±2 db. Size of
the transformers is similar to that of
standard octal metal tubes. Manufactured
by Microtran Company, Inc., 145 E. Mineola Ave., Valley Stream, N. Y.
C-9
Battery- Powered. Intercom. Operating
for months on a single self -contained dry cell battery, the Merco intercom system
uses four transistors in a printed circuit
and is recommended for distances up to
one mile. Power is used only when the syatern is actually in operation. The remote
professionals
choose
the
Sound engineers select the Roberts because its
recording and playback features fulfill the highest
standards of professional performance. Precision
elements that make for smooth, controlled operation
are Roberts calibrated V.U. meter, exclusive, new
MULTI -RASE HEAD (for full track erase in stereo
recording) and hysteresis synchronous motor.
Responding faithfully from 40 to 15,000 CPS, the
Roberts satisfies discriminating audiophiles in
their most exacting listening and recording needs,
STEREO RECORDER
$34950
NOW! RECORD
IN
STEREO
ROBERTS MATCHING
RECORDING AMPLIFIER
PROVIDES IDEAL SECOND CHANNEL PLAYBACK AND RECORD.
COMPLETE WITH ROBERTS
RECORDER
ROBERTS ELECTRONICS Inc.
1028 N. La
fis
Brea Avenue, Hollywood 38, California
CIRCLE 72B
$49900
s
station can signal the master station even
when the power Is off. The system is well suited for communication from building to
building, on the farm, at sports events, or
on construction Jobs where house current
is not available. Manufactured by Merco
Recording Company, Springfield Gardens,
C-10
N. Y.
Telectro 3 -Speed Tape Recorder. Speeds
of 1 %, 33/4, and 7% ips are incorporated
in the new Model 350 tape recorder recently introduced by Telectrosonic Corporation, 85 -18 37th St., Long Island City,
N.Y. It accommodates reels up to 7 Ins. in
diameter, and permits up to 8 hours of
playback time. A rotary-type selector
makes speed selection easy, and an interlocking device prevents any change of
AUDIO
72
www.americanradiohistory.com
MARCH, 1959
speeds while the machine is in operation.
A solenoid-actuated automatic shut -off
stops the recorder at the end of each reel
and returns all control to neutral. Frequency response is stated to be 50 to
15,000 cps at the 73¢ -ips recording speed.
Push -button controls are afforded for record, play, rewind, fast forward, and
FOR THE AUDIO PERFECTIONIST
!
Products which excel in design, in component quality, and in sound
Superior for monophonic use and fully compatible with stereophonic requirements
DYNAKIT MARK
*
pause. Other features include output jacks
for external speakers and amplifiers; inputs for microphone, phonograph, and
tuner; digital -type counter; level indicator. The Model 350 is housed in a handsomely-styled portable carrying case and
weighs only 27 lbs. It comes equipped with
microphone and stand, and a 7 -in. reel of
tape. For further information write to the
manufacturer at the address shown above.
Ei-Pi Cable Sit. To meet the requirements of component installations, a new
cable kit has been added to the audio accessories line of Anchor Products Company, 2712 W. Montrose Ave., Chicago 18,
Ill. Kit No. HK-510 consists of a 36 -In.
assembly due to uniquely
simple circuitry and printed circuit
construction with factory-mounted
parts.
* Highest stability suitable for all loudspeaker systems including electrostatic.
* Dyna Biaset (patent pending) for
simplified adjustment and complete
freedom from effects of unbalanced
components.
* Dynaco Super- Fidelity output transformer. This is the finest available
transformer of its type for the most
critical audio uses.
* 60 watts $79.95' net.
Mark III also available with added 70 volt
Mark III -70 $34.95' net
output.
C-11
III
Ease of
II 50 Waits
$69.75° net
MARK
DYNAKIT PREAMPLIFIER
* Finest quality available of circuitry and components.
* Lowest distortion and noise.
* Easiest assembly using pre-assembled printed circuit.
-
n yr Le
selected for
display at Brussels World's Fair.
* Only $34.95' net.
Power supply available for 2 pre -amplifiers PS -1 Kit $8.95* net
* Handsome styling
DYNAKIT STEREO CONTROL
* Adds
complete stereo control to two
preamps without noise or distortion.
shielded cable with pin plug and pigtails,
an 18 -in. shielded cable with two pin plugs,
a 72 -in. shielded cable with two pin plugs,
a double phono pin jack adapter, and a pin
jack to phone plug adapter. Various combinations can be assembled to make up a
wide range of audio cables.
C -12
Cabinet Leveler Sit. Comprising a precision level and four rubber -tipped screwtype feet, the Levelor kit makes it possible
to adjust a turntable or changer base to a
level position, which will improve record
fidelity and reduce wear. Installation re-
* Unique blend control
in middle."
* Level, balance, loudness, channel
reverse, and dual tape monitor controls.
* Only
N. J.
AUDIO
C-'13
$12.95° net.
Stereo control with two preamps
NEW DYNAKIT STEREO 70
*2
independent power amplifiers -35 watts
continuous, 80 watts peak on each channel.
* Unconditional stability using new DYNACO
A470 Super -Fidelity output transformers.
* All the features of the renowned Dynakit
Mark III, including exclusive Dyna Biases,
highest quality conservatively rated components, superb listening quality and handsome appearance.
* Can be assembled in 4 hours through use
of factory wired printed circuit assembly.
* Only $99.95° net including
quires drilling of four holes for the T -nuts
which are then pushed into place and the
feet screwed into the T -nuts. With the circular level installed on the motor board
surface, accurate leveling can be done in
minutes. Cabinart, 35 Geyer St., Haledon,
fills in "hole
cover.
Available from leading Hi -Fi dealers everywhere. Descriptive
brochure available on request.
*Slightly higher in West
DYNACO
E
X P
O
R T
INC.
D
611 N.
I
V
I
S
I
O N
[GREY FIRST
STREET
25 WARREN
MARCH, 1959
PHILADELPHIA
STREET
4,
PA
NEW YORK
LI
7,
S
N.
A
Y
73
www.americanradiohistory.com
NOW
2
SAVE HALF
ASSEMBLE-IT-YOURSELF
e99chdéei
NO
SPECIAL SKILLS
ELECTRONIC ORGANS
(front page 21)
Now you can afford an electronic organ. Whether you choose
the full Concert model or the smaller Consolette, you have an organ
equal to any made by the foremost manufacturers. In addition, you save
over t/ the cost because you assemble it yourself ...and you enjoy the
thrill of achievement. Too, you purchase each kit only when you are ready for it.
different MODELS
different SIZES
different PRICES
2
2
2
CONCERT
MODEL
{T TWO FULL SIZE PIPE-ORGAN MANUALS,
122 KEYS
* 26
{T
**
*
*
3'5" x 4'7"
FLOOR SPACE
STOPS AND COUPLERS
OCCUPIES
32 BASS PEDALS
ASSEMBLED CONSOLE
CONFORMS TO AMERICAN GUILD OF
ORGANISTS SPECIFICATIONS FOR PIPE
ORGANS
COMPLETE STEP -BY -STEP INSTRUCTIONS
CONSOLETTE
MODEL
**
{T
**
OCCUPIES ONLY 2' x 3'2" FLOOR SPACE
TWO FULL SIZE PIPE -ORGAN MANUALS,
-
122 KEYS
ABOVE -KEYBOARD TABS
22 STOPS
13 HEEL-AND -TOE BASS PEDALS
7 FULL OCTAVES OF TONE (DOWN TO 32
CPS)
**
BUILT -IN SPEAKERS OPTIONAL
ASSEMBLED CONSOLE
COMPLETE STEP-BY -STEP INSTRUCTIONS
{T
CARTRIDGE LOADING
PAY KIT -BY -KIT
before volume became excessive. This
inordinately large signal would often
overload the input tube if it were located prior to the gain control. Even if
the signal goes directly to the gain control, it is not a good idea to have the incoming signal so large that if someone,
for example a child, were to turn the
gain full on this would damage the
speaker or one's eardrums or both.
Most modern control amplifiers have
fairly high sensitivity on high level input. Seldom is this less than 0.5 volt and
often as low as 0.1 volt input for 1 -volt
output. Assume the control amplifier
has sensitivity such that 0.25 volt input
drives it and the power amplifier to
rated output, anywhere froid 12 to 60
watts or so. A typical piezoelectric
cartridge produces as much as 2 volts on
peaks. To reduce this to 0.25 volt entails
a reduction of about 18 db. Referring to
Figs. 2 and 5, shunt capacitance of 2100
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i
-1
Input Capacitance
Circle 74A
1
t
Response is 3db down at
frequency (about 8600
p,)
he e
Xc
equals
3684 ohms.
Fig. 4. Equivalent circuit of Fig.
ntQh
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Net
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fier.
Although the modern piezoelectric
cartridge can satisfactorily match the
RIAA recording characteristic when
properly loaded, many people still have
old records which were recorded with
LP, AES, and other recording curves,
and they wish to reproduce them properly. One way to meet this problem is to
adjust for differences between the RIAA
curve and other curves by means of the
tone controls, using one's ears to decide
when tonal balance is correct. Some
persons prefer to convert the pickup
into the equivalent of a velocity device
inasmuch as most control amplifiers,
RADIO. INC.
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µµf across a 500 -µµf cartridge reduces
its signal output 14 db by voltage divider action. This goes a long way to
prevent overdriving the control ampli-
.
built into the system. Instantaneous to
Treble Compensation
Bass Tone Control
Treble Tone Control
inc....
2 at high
frequencies showing how treble droop is
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25% deposit
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Circle 74B
Equivalent circuit showing how
shunt capacitance forms part of a voltage divider to reduce signal from piezoelectric cartridge.
Fig. 5.
AUDIO
74
www.americanradiohistory.com
MARCH, 1959
stereo as well as monophonic, provide a
variety of equalization characteristics
for velocity (magnetic) pickups.
LARRY ELGAIIT at the CONTROL CON SOLE of his !E EC'O R DING STLTDIO
(Note the AR-I monitor
loudspeakers, in stereo)
Converting to Velocity Device
One method of converting the piezoelectric cartridge into a velocity device
is by loading it with a relatively small
resistor, on the order of 47K ohms or
less. Such a resistor in series with the
cartridge capacitance produces a high pass characteristic, in the same manner
as illustrated at (B) in Fig. 2 in connection with bass cut. Now, however, the
very small resistor causes high -pass action through all or most of the audio
range, thus producing a rising response
at the rate of 6 db per octave in the
manner of a magnetic cartridge. Then
the signal can be fed into an input designated for a magnetic pickup.
The above procedure contains a pitfall, and care must be exercised to avoid
it, for otherwise one will have an undesirable treble peak. High fidelity
piezoelectric cartridges generally have
a built -in treble hump, achieved by
damped resonance, which produces a
satisfactory approximation over most of
the upper range of the treble boost required when reproducing an RIAA disc
with an amplitude pickup (see Fig. 1).
If the pickup is used instead as a velocity device, this rising characteristic
remains. However, by avoiding too small
a load resistor, high -pass action can be
limited in the treble range, offsetting the
treble hump of the cartridge. Manufacturers of piezoelectric pickups will generally supply users with information on
the preferred load resistances for use
of their product as a velocity device or
as an amplitude device. Moreover, for
smoothest response, they will frequently
supply users with a schematic or ready built adapter which contains a suitable
loading network to convert the pickup
into a velocity device and simultaneously
reduce the treble hump to an insignifiemit quantity.
LARRY ELGART, RCA VICTOR RECORDING ARTIST
One of
the most exacting jobs for
a
speaker system is that of studio monitor
in recording and broadcast work. Technical decisions must be made
WORKSHOP
(from page 31)
tweeter. It works, though he insists it
needs improvement. A week later he
confidently outlined plans for a full range electrostatic speaker.
Some of the wilder types have gone
deep into left field, turning out such
jabberwocky as an electronic gunslinger
who always beats you to the draw, and
a perverse electronic hand which, when
you turn a switch on, comes out of the
box and shuts it off.
But the main theme is high fidelity.
This is natural. The guiding spirits of
the Workshop are both audio technicians
and high fidelity fans. Elliot Gordon devotes part -time to the Workshop, func-
AUDIO
on the basis of the sound coming from these speakers, which will
for good or for ill, the quality of a record master or FM broadcast.
affect,
acoustic suspension speaker systems, although designed primarily
for the home, arewidely employed in professional laboratories and studios.
Below is a partial list of companies using AR speakers (all models)
as studio monitors:
AR
Down Records
Con certopes- Concertdisc
Elektro Records
WGBH
Mastercraft Record Plating
Canterbury Records
WPFM
Raleigh Records
Counterpoint Recordings
(formerly Esoteric Records)
Magnetic Recorder and Reproducer
Dubbings
Concert Network stations
WBCN, WNCN,
WHCN, WXCN
AR
WXHR
speaker systems, complete with enclosures-the AR -1, AR -2,
and AR -3-are priced from $89 to $225. Literature is available
for the asking.
ACOUSTIC RESEARCH, INC.
MARCH, 1959
24 Thorndike Street, Cambridge 41, Mass.
75
www.americanradiohistory.com
Dimensions:
16V," deep.
17" high, 24" wide
Germany's foremost manufacturer of high quality speakers presents:
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A
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The RONDO enclosure uses the Helmholtz principle and is a direct
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Using the two -way ISOPHON PH 21
Applying a polarloading technique that achieves a remarkable,
low frequency response.
Eliminating narrow beam radiation of high frequencies. Independent of room placement.
Cabinet made of finest West Indian mahogany in various finishes.
In its size and price class, this unit is an unsurpassed performer for both,
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This is just one of many ISOPHON models.
Write for more details and beautifully illustrated brochure.
ISOPHON SPEAKER DIVISION, Arnhold Ceramics, Inc.
achieve a divorce. He has since decided
that 60 db will be adequate so long as
he can also keep his wife.
East 57th Street, New York 22, N. Y.
1
Do you know where you can find information about
the current articles in magazines about microwaves, loudspeakers, television
repairing, electronic musical instruments, traveling -wave tubes, transistor
amplifiers, oscilloscopes, or any other electronic subject?
THE OUESTION:
THE ANSWER:
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tinning as an audio -man at the Columbia
Broadcasting System television studios.
He landed at CBS in 1953 after service
as a Navy communications officer and
the achievement of a Master's degree in
Romance languages in Paris. Dave Muir head's story is more devious. It includes
gandy- dancing on the railroad, covering
MP beats in the Army, short -order cooking, and riding gain on P.A. systems in
theaters.
In 1957, while at the RCA Institutes,
Muirhead responded to a call for an
audio technician from the well -known
off -Broadway Shakespeare Theater. It
turned out to be Elliot Gordon who had
issued the call. The two men met and the
Audio Workshop idea was born. The
following spring saw its reality.
Dave Muirhead opens the place at 11
a.m. Traffic turns brisk by late afternoon and stays so all evening. (Their big
trouble, both agree, is routing the patrons out at 11 p.m., closing time.) Talking shop and auditions of systems are
continuous run features, and it's hard to
tell just where you came in. It's easy to
spend time there. One habitue finally admitted that if he stayed long enough to
achieve a noise and hum level 90 db below signal he would probably also
!
RADIO MAGAZINES, INC.
Mineola, N. Y.
629,
Someday -a Chain of Workshops?
Muirhead and Gordon are simply consolidating the gains the Workshop has
made so far, for the present. But, of
course, they have plans. There's an audition room they want to build. They are
talking seriously of running lectures on
all aspects of sound. They're thinking
of scheduling demonstrations of new
equipment. Moreover, they are interested
in spreading the Audio Workshop idea
to other regions. They are eager to share
the valuable experience gained in this
pioneer effort. And they cite the savings
to be gained by several Workshops purchasing as a unit and advertising co-
operatively.
Dave Muirhead expresses their approach when he explains "We went into
this because we enjoy high fidelity so
much that we thought others who enjoy
it as much as we do but who have no
facilities at home would take to the idea.
We also felt it would be a pleasant and
friendly way to make a living." And
that feeling permeates the Workshop. It
is friendly, no one hurries you, no salesman prods you to buy anything.
But, one thing they insist on. Woodwork is out. "No facilities" claims Muir head. "He really means we just don't
want to get involved with hammers and
saws and drills" Corrects Gordon. `Besides" adds Muirhead, "who could hear
the music for the hammering'?"
AUDIO
76
www.americanradiohistory.com
MARCH, 1959
PROFESSIONAL PERFECTION!
DECIBEL
(from page 27)
The points brought out in the preceding paragraph can best be illustrated by
means of some examples. Figure 3 shows
a step -up transformer in which the primary voltage is 100 and the secondary
voltage is 500 volts. To use the above
formula without regard to its true
meaning and the restrictions imposed on
it would lead to a "voltage gain" of almost 14 db. As there is no power gain,
the use of the decibel is meaningless and
shows what an indiscriminate use of a
formula can lead to. Many older textbooks still contain examples in which the
voltage gain is calculated in this manner. Of course, this should not be confused with the voltage gain of an amplifier stage in which the output voltage is
divided by the input voltage giving rise
to a number representing the stage gain.
This is perfectly legitimate; the trouble
arises when the decibel is made to serve
as a measure of stage gain.
Figure 4 illustrates another example
of the incorrect use of the formula. The
input and output voltages are equal and
improper use of n =20 log EI /E2 would
give zero gain as the result. But the input power can be seen to be 0.625 milli watt and the output power is 6.25 watts,
resulting in an actual gain of 40 db.
The situations illustrated in Figs. 3
and 4 are typical of the results obtained
when certain restrictions are disregarded. Decibels are always used to
measure power gain; voltage gain in
this sense is meaningless. The two expressions
u =20 log E, /F.2
and
n =20 log 11/12
are merely short -cuts to calculating
power gain and furthermore can only he
used when the resistances across which
the two voltages were measured or
through which the two currents are
flowing are equal. This restriction was
disregarded in a recent textbook problem on antenna gain. A folded dipole
developed a signal of 150 microvolts
while a rhombic anténna, receiving the
same signal, developed a signal of 700
microvolts. Use of the formula in the
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than 0.25% at
For further details write 3. A transformer can step up a
voltage but cannot produce a power
gain. Hence, using n = 20 log E, /E_ to
get the voltage gain in db is meaningless
as the decibel is reserved as a measure
of power gain.
Fig.
AUDIO
AMERICAN CONCERTONE
AUDIO DIVISION,
C U L
AMERICAN
ELECTRONICS, INC.
WEST J E F F E R S O N B
V E R CITY,
CALIFORNIA
9 4 4 9
MARCH, 1959
O U L E V A R D
DEPT
A3
77
www.americanradiohistory.com
.
,....:::.
--
pmLon.eer
-
,.
preceding paragraph yields a gain of
13.4 db whereas the gain is actually only
10.4 db. The explanation lies in the fact
that the characteristic impedance of the
two antennas is not the same. A folded
dipole has a characteristic impedance of
300 ohms while that of a rhombic is 600
ohms.
Recapitulation
SM -R
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St ereo,
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Specifications
PIONEER's all-new Stereomaster SM -Rl50
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Moreover, Hi-Fi ensembles, using either
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Circuitry:
:
OARS push -pull 2 amplifiers
in one compact chassis.
involved
watts per channel for stereo (15
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Hum. -53 db below maximum output on
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Frequency Response: -- 0.5 db, 20- 20,000 cps
Equalisation: RIAA 8 MARTS (NF type)
Inputs
TAPE, PHONO (MAGNETIC 6 CRYSTAL),
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AUX
Channel Filter:
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FUKUIN ELECTRIC
MONARCH INTERNATIONAL,
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Nor ill Hollywood,
We can now turn with profit to some
of the statements mentioned at the beginning of this article and interpret
them in the light of what we have
learned. When amplifier specifications
read : 5 cps to 160 ke., within 1 decibel,"
what is meant is that if the power output
at any frequency in this range is compared to the power output at 1000 cps
they will not differ by more than 1 decibel. Or to say that the "response is down
only 3 db at 200 ke" means that the gain
of the oscilloscope's amplifier at 200 ke
is only one -half that of its tnidfrequency
range. (A 3 -db loss means the saine as
half- power, and a 3 -db gain represents
twice the reference power.) When the
power output of a microphone is given,
it always refers to a power of 1 milli watt as the reference. For an output of
- 60 db, the power output would be 10 -8
watts?
California
Noise and Hum Ratings
CrreN 7aA
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in
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2
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Directional Characteristics: Omnidirectional, Cardioid, Bi- directional
Sensitivity: 0.8 mV /dyne /cmr
Front to Back Rejection (Cardioid):
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three patterns: omnidirectional, bi- directional
and cardioid.
When a manufacturer states that his
amplifier has a hum level -90 db below
20 watts he means that when the output
of the amplifier is 20 watts the power
level of the hum signal is 0.02 micro watts. The hum present in the output of
an amplifier is quite often measured in
decibels and this might have been done
in the circuit shown in Fig. 4 using the
following procedure. Suppose the signal
voltage (at 1000 cps) across the plate to-ground circuit measures 100 volts.
And further that a harmonic wave analyzer set to 60 cps measures 5 millivolts
=10 log .001 /P
P =10 -9 watts
60
> 20db.
Output Impedances: 50 or 250 ohms
Distortion: <0.8% entire range
Size: 7A" dia. x 6" long
Weight: 5 ozs.
Matte Satin Chrome
The KM-56 Microphone System consists of the
following components:
KM -56 Miniature Condenser Microphone
NKM Power Supply (U. S. Std. fuse, pilot, XL
connector, AC plug)
KC -1 25 ft. Microphone Interconnect Cable
Z -311 Full -elastic Suspension:
6 ft. AC Power Cord; mating XLR -3.11 output
10v.
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udio
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Circle 78B
Fig. 4. This stage has a gain of 40 db,
but improper use of the same formula
illustrated in Fig. 3 would indicate that
the gain is 0 db. The text points out that
the voltages must be measured across
equal resistances for this formula to be
valid.
AUDIO
78
www.americanradiohistory.com
MARCH, 1959
at full amplifier output. Then the hum is
found to be down -80 db.a
Summary
Hence we see that the decibel is used
as a means of comparing two values of
power. It can be used to compare the
input and output power of an amplifier,
resulting in the db gain of the entire
circuit. Or, what is usually more important, it is used to compare the power
output at some specified frequency with
the power output at many other frequencies in its intended range. Here the
decibel is used to compare these values
and the result, when plotted, becomes
known as a universal response curve.
Gain or loss refers to power levels above
or below the reference power; input always remaining constant. The value of
the decibel is in comparing power levels
without the need to refer back to actual
values of power.
When two voltages are measured
across equal resistances they can be used
to calculate the power gain. Much confusion has arisen in the past by calling
the result "voltage gain." Actually, this
is merely a short -cut to finding the
power gain, measured in decibels.
The decibel is a useful tool in the
analysis of electronic equipment. It
enables comparisons to be made quite
readily and "normalizes" the many
variables present in a circuit under inspection. Its present use transcends the
earlier concept of the logarithmic reÆ
sponse of the human ear.
3
Worth waiting for
You've waited because
-$0 log (100 /0.010)
n = -80db (- signifing that hum power
n
is less than signal power)
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March 15- 18- Annual Convention, National Association of Broadcasters. Conrad Hilton Hotel, Chicago, Ill.
March 23-26--National Convention, Institute of Radio Engineers. The Coliseum
and Waldorf- Astoria Hotel, New York.
April 6 -9 -Radio Electronic Components
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AUDIO
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MARCH, 1959
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www.americanradiohistory.com
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Handel- Reflections
MONTH will signalize the 200th
anniversary of the death of George
Frederick Handel, and since everyone
seems impressed by round figures (as
Howard Taubman recently pointed out in
his Sunday column, "Anniversary Daze "),
a little more Handel probably will be performed this year than during previous
years. But judging from all indications, we
are not about to witness a wholesale revival
of the German composer's music. To be
sure, Messiah will again be heard, along
with the Largo, some of the Concerti Grossi,
and a few odd excerpts from his dramatic
works. Perhaps some magazine editor will
get Sir Thomas Beecham to repeat his well
known attacks on the Handel "purists."
And, in the world of microgroove, don't be
surprised to find a smattering of Handel
issued piously under a Bicentennial banner.
So far, the occasion does not seem to
have set the musical world aflame. No
counterpart of the late Duncan Robinson
(former secretary of the Berlioz Society)
lias been making urgent phone calls to
music editors, artist -and- repertoire directors, book publishers, and conductors,
pressing for more recognition, more performances, and more recordings of the
shamefully neglected works of a great
composer. No influential music critic has
declared himself for Handel in the manner of an Olin Downes championing the
cause of Sibelius. In song recitals, Handel
connes first on the program, but last in importance; singers use his arias as warm -up
pieces and frog -chasers, while the latecomers find their seats.
No one will challenge the fact that
Handel was one of the giants of 18thcentury music. Yet the picture the general
public has formed of the Saxon composer
bears little resemblance to the true nature
of his genius. Handel usually appears on
concert programs through the good offices
of a trio of knight -conductors, Sir Thomas
Beecham, Sir Hamilton Harty, and Sir
Henry J. Wood, each of whom arranged
numbers of Handelian scores for the
modern symphony orchestra. These transcriptions are highly effective in their own
way and have kept Handel in the orchestral
repertoire, albeit in modern dress. As for
the oratorios, the Crystal- Palace tradition
of performing Handel is, unfortunately,
still with us. Gone are the days when 4000
singers and instrumentalists participated in
a single performance of Messiah, but the
"big" approach has not been abandoned
altogether. "Suppose Handel were living
today and saw our large halls," stated Sir
Thomas Beecham, "and had full acquaintance
with the resources of the modern
orchestra
what would he have done?
My own personal answer: he would
NEST
...
...
26 Ii
...
\-into St., Nrw York 11, N.
Y.
on a Bicentennial
have used every confounded instrument
there was that he could lay his hands on
and a few he couldn't."
During the two centuries since Handel
died in London on April 14, 1759, his
music has been re- harmonized, re- orchestrated, and reshaped to conform to prevailing tastes. Time sanctified many of
these revisions, and the "Handel tradition"
was born. While Handelians manage to
stage "authentic" revivals from time to
time, the task of musical direction is
usually assigned to dull, if well- meaning
conductors. (There are, of course, notable
exceptions, although the world's outstanding conductors seem to prefer hyphenated
Handel-Handel -Harty, Handel -Wood, etc.
pure Handel.)
As a result, only a tiny handful of works
from the output of this staggeringly prolific master is heard today in its original
form. Probably the most neglected area in
Handel's production is that of opera.
Handel composed over forty musical dramas
and none of them are in the standard
repertoire. This is ironical in view of the
fact that he was one of the greatest
dramatic composers of his time. The reasons
for Handel's absence front today's operatic
stage are numerous and complicated -so
complicated, in fact, that even the most
ardent Handelians throw up their hands in
despair at the thought of coping with the
difficulties of staging these fascinating,
though curious works.
The element of curiousness is due partly
to the rigid operatic conventions of Han del's day, and partly to the enormous popularity of the castrato singer.
First, let us examine the libretti that
were written for Handel's operas, and for
those by other composers in early 18th century London. With few exceptions, they
dealt with classical subjects, as well as with
later -Roman Empire themes, and mythology. Plots were absurdly complicated,
dialogue was stilted, and characterization
shallow. The burden of the plot was assumed entirely by the recitative; the aria
expressed only a single thought or emotion.
There was little or no action throughout
the work ; the visual interest lay in elaborate sets and spectacular scenic effects such
as waterfalls, storms and, in at least one
-to
instance, birds.
In his excellent biography of Handel
(Alfred A. Knopf), Herbert Weinstock describes the castrato as a "boy's voice produced by a man's lungs with the resonance
of a man's body, and projected -by the
greatest castrati -with the art and comprehension of a mature musical mind." In
Handel's time, the castrato was the equivalent of the later prima donna, and the mere
appearance of a Nicolini, for example, in
the cast virtually guaranteed a full house.
AUDIO
80
www.americanradiohistory.com
MARCH, 1959
The da capo aria, so detested by modern
audiences, was designed for the virtuoso
singers of that period, who did not simply
repeat the melody, but provided it with
florid improvisations. Today's audiences
would also find another convention hard to
take: the leading singer always leaves the
stage immediately after performing one of
his big arias, which leaves the librettist in
a fine dramatic pickle.
The chief stumbling block to modern
performances of Handel's operas is obviously: what to do with the castrato part?
One possibility is transposition to another
key, giving the role to a tenor ; but this
wreaks havoc with Handel's key relationships. The key need not be altered, however,
when the part is transposed an octave lower
for a baritone, but the tone-color is radically affected. Range can be preserved by
assigning the role to a soprano, but this
upsets the dramatic values. There is, of
course, no substitute for the sound of the
castrato voice, which, according to all accounts, was of a silvery, trumpet -like
ndtilt9 the
to
audiophilesreproduction*
internationally
iheiwó
ip
ultimate
requirern
`heebxar tying
st turntable
and
he fr^
Tit e ae d as the
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ealer of
dealer
honored fl d to
your
Y°
visit
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reProduction you
b QeneModified
selection
stereo
ilent precision
invite
your
deptlt'
cordially
p1aYs
remarkably
We
as it and majestic
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lot
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t
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the Connoisseur
wt
with
...
meets
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stereo
'
*Obviously
non-stereo
¿
tt
es
record rep
texture.
These formidable problems should not
obscure the fact that Handel lavished his
most creative energies in opera composition
for some 35 years. After all, he was not
the only composer saddled with inferior
texts. Handel's operas contain incredibly
rich musical experiences. If, to uncover
them, we must accept the conventions of
another operatic age, by all means let us
do so. It's a small enough price to pay for
bringing to life some of the most compelling dramatic music ever written. Æ
CONNOISSEUR MODEL B
TRANSCRIPTION TURNTABLE
MADE IN ENGLAND
As always, in limited quantities
t
16 W. 46
la Canada: Astral Electric
NEW LITERATURE
Pilot Radio Corporation, 37 -50 36th St.,
Long Island City 1, N. Y., announces the
publication of a new booklet titled "Stereo
and You." In "Stereo and You," Pilot has
endeavored to answer questions which
dealers and the public have been confronted with since the introduction of
stereophonic sound. Your copy of this interesting and worth while book will be
mailed free upon written request. C-18
Sweeten* Corporation, Elmsford, N. Y.,
explains the entire process of stereo recording and reproduction in a new pocket size booklet titled "Stereo Simplified."
Intended to help music lovers who are
interested in purchasing new stereo equipment as well as those planning to convert
present monophonic sets, this booklet will
be of great value to the person who is still
wondering just what stereo is all about.
C-17
Viking of Minneapolis, Inc., 9600 Aldrich
Ave., South, Minneapolis 20, Minn., now
has available for general distribution a
new accessories catalog. Listed and illustrated is a wide range of items which add
greatly to the flexibility of the Viking 75
and 85 Series tape decks. Of particular
interest is the "88" speaker, providing as
it does a small -area source along with
better -than -average speaker performance.
C -18
Ne:icon Electric Company, 266 W. Clay
Ave., Roselle Park, N. J., announces a new
catalog sheet covering Long -Life soldering
iron tips. Shown are 81 new shapes and
sizes, a total of 124. Included are plug tips
from 1/16" to 1%" and screw tips from
7/16" to 1%" diameter. Various tip shapes
are illustrated, complete dimensions are
given, as well as advice on use and care.
Also included are list prices. If you use
soldering iron tips industrially, this listing will probably mean great savings. C-19
AUDIO
MARCH, 1959
.
.
.
ERCONA CORPORATION
Electronic Division)
Street, Dept.
Co. Ltd.,
20. New York 36,N. Y.
Danforth Road. Toronto 1.1
:l
AN IMPORTANT MESSAGÉTo audio engineers, music enthusiasts, and students interested in the science of
Acoustics and Musical Instruments.
From the distinguished Acoustical Instrumental Studio in Gravesano, Switzerland comes
the-
GRAVESANER BLATTER /GRAVESANO REVIEW
(English /German Edition) Edited by Hermann Scherchen
.. dedicated to the contribution toward the more perfect reproduction of music through the
science of acoustics and musical instruments. The GRAVESANO REVIEW is edited by
.
Professor Hermann Scherchen, noted European conductor and musicologist. It begins
its third year with Volume IX, reporting the meetings of the Acoustical Experimental
Studio in Gravesano, Switzerland. Issued quarterly, subscription is now available in the
United States by special arrangement with Radio Magazines. Inc., publishers of Audio.
You may begin your subscription with Volume IX of the GRAVESANO REVIEW
which is combined with the GRAVESANO SCIENTIFIC RECORD, a 331/2 rpm LP
demonstration record.
i
¡ -)"
Partial list of contents in Volume IX:
r
(all articles appear in both English and German )
r
The Modulor, Concentration instead of Expansion, Acoustics and Large Orchestral
Studios and Concert Halls, Psychoacoustical Phenomena accompanying natural and
MAGAZINES,
synthetic sounds. The Ear-a time measuring instrument,Experience with a new high
INC., SUBSCRIPquality loudspeaker for control booths. Tuning the Oboe. Accompanying Volume
IX: THE GRAVESANO SCIENTIFIC RECORD contains a demonstration of
TION DEPT. GBA
the Frequency Regulator of Anton Springer of Telefon-Und Apparatebau AG..
P. O. BO X 6 2 9,
Frankfurt /Main.
MINEOLA, N. Y.
;
RADIO
'
i
¡
Issued quarterly, THE GRAVESANO REVIEW is accompanied with
GRAVESANO SCIENTIFIC DEMONSTRATION RECORD.
a
Single copies not for sale, by subscription only, $6.00 per year, postpaid.
,
Exclusive United States Subscription Agency:
RADIO MAGAZINES, INC.
MINEOLA, N. Y.
I
i
www.americanradiohistory.com
I
Please enter
subscription to GRAVESANO
I' REVIEW
and accompanymy
mg SCIENTIFIC DEMON-
STRATION RECORD.
Name
itAddress
City
I
enclose the full remittance of
$6.00.
Zone
State
TRANSFORMERS
where
ne sound
begins!
Fine sound reproduction begins with
a good microphone. Reslo microphones bring out the best in your
recorder with unsurpassed quality
for clean, silky, uncolored, flat response to 20,000 c /s.
Quality recording, broadcast or P.A.
uses require a Reslo Mark Ill. Blast proof, fully shock mounted, triple
shielded for outdoor use, they can
be boom mounted without adaptors.
Exclusive ribbon permits near automatic self- service replacement.
Resto microphones are used by leading broadcast and recording firms.
Try one at our expense... see your
dealer.
4
Complete data and price lists
for qualified respondents.
ERCONA
(electronics
dept.
A -3
div.)
16 West 46th St., New York 36
World's
Finest
CIRCLE 82A
s ave on
Stereo
hi-fi
see the best values in the
1959
ALLIED CATALOG
world's
largest choice
of systems and
components...
everything in
STEREO!
Here's your complete, money - saving
guide to Hi -Fi! See how you save on
ALLIED -recommended complete systems,
including the latest in thrilling Stereo.
Choose from the world's largest stocks
of components (amplifiers, tuners,
changers, speakers, enclosures, recorders, accessories). Want to build -yourown? -save up to 50% with our exclu-
sive Hi -Fi KNIGHT -HITS! Easy terms
available. For everything in Hi -Fi, for
everything in Electronics, get the 452page 1959 awns Catalog!
ALLIED RADIO
a4IPtiea.Ó14t-ÇÌ. Cutivc,
r
ALLIED RADIO, Dept. 146 -C9
100 N. Western Ave., Chicago 80, III.
Send FREE 1959 ALLIED Catalog
Name
Address
City
Zone
V
State
(front page 46)
made for these several core materials.
A pure sine -wave voltage was produced
across the coil while the corresponding
distorted energizing current was analyzed. To accomplish this, the transformer was included in a negative feed hack loop with a very large feedback
quotient from an unloaded winding on
the transformer. This maintained an exceedingly pure sine -wave flux -density
variation. The energizing current was
passed through a resistor. The voltage
across this resistor, being proportional
to energizing current, was analyzed.
Measured in this way, the distortion in
the energizing current depends only on
the core material and the flux density.
These measurements were restricted to
high flux densities by amplifier noise and
related problems, so that complete curves
could not be obtained. The high -level
comparisons thus made are very helpful.
In Figs. 1 and 3 the permeability peak
occurs at 3500 or 4000 gauss. The energizing currents at 3500 gauss for Audio
A silicon steel, low -grade silicon steel,
and 4750 nickel alloy respectively contained 16.3, 15.5, and 13.0 per cent third
harmonic. This is a rather small variation and indicates that distortion calculation at the permeability peak as determined by impedance measurements
alone, without knowledge of the core material, would generally be reasonably
accurate. At high flux densities the distortion varies rapidly with changing
level, reducing the accuracy of such
comparisons. Distortion produced in
vacuum tubes does not usually agree
with calculated values, or published values, much more closely.
Curiously, the distortion at the low level peak equals the distortion at the
permeability peak for these lamination
materials. The maximum low level distortion for Audio A, Fig. 1, is about 10
per cent third harmonic. At 4000 gauss,
the permeability peak, the third harmonic is again about 10 per cent. This
relation is also found in 4750 alloy and
Mumetal. Also the low -level distortion
peak in each case is at roughly one
hundredth the voltage of the permeability peak. Having determined the voltagè
at which the impedance is maximum,
and knowing the relative impedances of
transformer and circuit at the permeability peak, the distortion at any flux
density can be estimated. The accuracy
will be best at low flux densities because
those portions of the distortion curves
are nearly flat. These relations do not
hold for grain oriented tape cores which
have distinctly different permeability
curves.
To compare transformers designed for
the salve application, simply measure
the energizing currents at the voltage
and frequency of interest. The distortion
ratio is very likely to be about the saine
as the ratio of energizing currents. In
the case of output transformers it is most
unlikely that the distortion ratio will be
less than the energizing current ratio,
but it may possibly be greater. The
transformer with lower energizing current is likely to have more turns or a
larger core. In either case the flux density will be lower, further reducing the
distortion at high voltage levels. With
low -level transformers the exact flux
density has little effect on the distortion,
and the accuracy of this simple comparison will be better.
High-quality low -level transformer
cores are generally a material similar
to 4750 or Mumetal. Transformers designed to handle the same amount of
power, using either of these materials,
can be compared on the basis of energizing currents alone with particularly
good accuracy because the respective distortion curves are so very similar in
shape. The difference in saturation
points does not enter this comparison if
the transformers actually handle the
same amounts of power.
In choosing transformers, the heaviest
or largest is likely to have the best low frequency characteristics in the usual
case where the core materials are similar.
Core material and copper account for
much of the transformer cost. Additional
material is not intentionally used unless
it provides a commensurate improve ment in the transformer. Of course a
large case sometimes contains a small
transformer.
Transformers Preferably Avoided
Because audio transformers introduce
amplitude and frequency distortion and
waste power, they should be avoided
when possible. It is not unusual for the
elimination of one transformer to make
a noticeable improvement in sound quality.
Certain transformer types are particularly objectionable. In designing a
high-impedance transformer, high -frequency considerations limit the amount
of inductance which can be provided.
High -impedance audio transformers depend on properly damped resonances to
extend the high-frequency range. An
increase in coil turns or coil sizes reduces the frequency of these necessary
resonances and thus reduces the high frequency span. Therefore the more difficult the high-frequency problem, the
more the low- frequency response suffers.
Of the common transformer types,
the most undesirable from a distortion
standpoint is the high -level interstage
transformer. The secondary impedance
CIRCLE 828
AUDIO
82
www.americanradiohistory.com
MARCH, 1959
PROFESSIONAL.
DIRECTORY
9fridops1nut
HIGH- FIDELITY HOUSE
Most complete stock of Audio
components in the West
Phone: RYan
536
S.
FMAZ
ANTENNAE
II
Get more FM stations with the world's most
powerful FM Vagi Antenna systems.
Send 25, for booklet -Theme And
lions" containing
APPARATUS
FM
Van.
Station Directory.
DEVELOPMENT
CO.
Wethersfield 9, Connecticut
Circle 87D
LOOK
further
.
if you're
searching for hi -fi savings.
Write us your requirements now...
Key Electronics Company
no
120 -K Liberty St., N.Y. 6, N.Y.
EV 4 -6071
Circle 87E
BUYING HI -FI?
LOWEST PRICES
PLUS RELIABILITY!
GET
For surprising quotations. write
your list of hi -fl requirements.
We promptly ship fresh,
late
serial, sealed cartons, mfg's
equipment.
Sane
c
LACYFS
N. 6th
ELECTRONICS
St.- Richmond,
Vo.
Circle 87F
-
and Accessories
&LECTRO-UO10E
SOUND SYSTEMS
126 DUNDAS ST. WEST, TORONTO, CANADA
Circle 87G
th( finest *,cII -I'
t!t'iR(f
LO)/07CC6
SOUND
, O> , ,i
820
W.
AUDIO
O le
c
L
A. 15,
Circle
8711
Olympic Blvd
IRPM SETS TUNER MEASUREMENT
STANDARDS. The Institute of High Pidelity Manufacturers has opened its program of establishing measurements standards within the industry with distribution
of a booklet entitled "Standard Methods
of Measurements for Tuners." Prepared
by the Institute's Standards committee,
the booklet defines FM and AM terminology, operating conditions, requirements
and characteristics of testing devices, FM
and AM test procedures, and test procedures for AM /FM tuners. The booklet is
available from the Institute at a cost of
one dollar.
ALTEC JOINS LING GROUP. An agreement on terms for the acquisition of Altec
Companies, Inc., stock by Ling' Electronics,
Inc., has been announced by James J. Ling
and G. L. Carrington, board chairmen of
the two companies. Upon completion of
the transaction, Altec Companies, Inc.,
and its subsidiary, Altec Lansing Corporation, will both operate as subsidiaries of
Ling Electronics, Inc., and Altec Service
Company will continue as a division of AItec Companies, Inc. There will be no
change in the commercial operations, management, name or policies of the Altec
organizations.
-,
MIGM F.OELITY
C
ARRAY IN LARGER QUARTERS. Arkay Radio Kits, Inc., has moved to new
and expanded quarters at 88 -06 Van Wyck
Expressway, Richmond Hill 18, N. Y. According to Irving Becker, Arkay president,
the move reflects the tremendous popularity of hi -li kit construction among music
lovers and hobbyists. Arkay will have
more than 30,000 sq. ft. of space at its new
site. Plant and equipment will provide
every modern facilitiy for hi -ft and component production, with complete engineering, testing and servicing laboratories.
TELADI
CONDENSER
MICROPHONES
%t1`t,
x225°°
Cilil
MARCH, 1959
AI
N
J. A.
Matthews
-J. B. Minter
Professional Sound Recording Services:
Disk mastering, Tape Editing, Dubbing, etc.
I
.0211
COMPONENTS CORPORATION
-
Recording Division
Denville, New Jersey
OA
Circle 87K
TEN'
complete with
TELADI
power supply
8 all cables
Newest Condenser
Microphone
receives praise
from professional
users!
The
he TELADI Condenser Microphone from
West Germany was recently introduced to the
American Market and because of its unusually
smooth and wide -range response, its variable
output and other exclusive features, it has already gained a reputation for top performance
. and yet it costs only about half as much
as other similar micropones.
Typical comments we have received:
"I've been using two TELADI microphones
with a Tandberg stereo recorder to make professional recordings of Choral groups and
legitimate pipe organs. The results have been
outstanding . . . the extreme low frequency
range, such as the pedal tones of the pipe
organ, are unsurpassed."
"We are using the TELADI to broadcast
and record live musical programs on our FM
station
. which
covers a wide variety of
material. We have received many fine comments on the clean crisp sound of our live
shows for which the TELADI is responsible."
Send
A.
for full particulars and name of your
dealer.
Precision Product of Western Germany
Sole mportera for the United S ate
MAI\ r
company's general funds.
CANADA
High Fidelity Equipment
Complete Lines
Complete Service
Hi -FI Records
Components
(' (it
MUTER ENTERS CARTRIDGE FIELD.
Long known as a manufacturer of quality
component parts, The Muter Company,
Chicago, has begun production of two ceramic stereo cartridges for the original
equipment manufacturers market. Produced under a license agreement with
CBS -Hytron, the units will be marketed
solely by the Muter sales organization
directly to manufacturers. The two cartridges are said to have wide frequency
response, low tracking force, and channel
separation in excess of 20 db. The two
models are identical in construction, differing only in polarization of the ceramic
elements.
ELECTRO -VOICE WILL REGISTER
STOCK. Electro- Voice, Inc., has tiled a
statement with the Securities and Exchange Commission asking sanction to
register 150,000 shares of capital stock.
Sale by shareholders will account for
75,000 shares, while the remainder will be
offered for the account of the company.
Net E -V sales for the nine -month period
ending November 30, 1958, totaled $8,493,419 and income was $415,826. Net proceeds
from the share sales will be added to the
on
shipping!
1
AUDAZ BUYS BACON HI -PI. George
Silber, president of Rek -O -Kat Company,
recently announced the purchase by HekO-Kut's Audax Division of the hi -fl
speaker manufacturing facilities, inventory and tools of Bacon Electric Company.
Mr. Silber also revealed his intention of
entering the packaged high fidelity field
within the near future, possibly later this
year. The new loudspeaker line will be
Fair Oaks, Pasadena 1, Calif.
Circle 87C
warranted
.
marketed under the Audax trade name,
along with Audax cartridges and tone
arms.
-8171
1
Noí,es..
SOUND
COMPANY
New York, N. Y.
80 W. 55 St.
Circle 87A
We Don't Make AMPLIFIERS!
"tops" in high fidelity
transformers. many engineering friends look to as
for the ideal amplifier circuit. We spent eighteen
months in engineering such a circuit and finally
resolved this ideal amplifier into kit form. This Is
our MLF kit (pretested printed circuit auembles
in 20 minutes), 99.50 net.
We do not catalog this kit, but word of mouth
has caused
a gradually increasing demand
from
professionals like WQXR for this Ideal (only 20
watts) amplifier for broadcast, recording, hl -i. If
you are interested. write for YLF shut
11
you already know about it order from year legal
jobber (he won't have it In stock, since productbn
Because or our position as
.
is
small).
UNITED TRANSFORMER CORP.
7 -0290
150 Varick St., N.Y 13, N.Y.
o.
x
Circle 87B
87
jJjQ
ueCLf
lipe1--
/
LAFAYETTE
STEREO TUNER KIT
_-
THE
MOST FLEXIBLE TUNER EVER DESIGNED
MuRifles Output ter New Steno FM
11
Tubes (including 4 dual. purpose) +
Tuning Eye + Selenium rectifier Proide 17 Tube Performance
Pre -aligned IF,
10KC Whistle Filter
Tuned (mode FM
12 Tuned Circuits
Dual Cathode Fell,.., Output
ly Tuned FM and AM Serrions
Armstrong Circuit with FM/AFC ood
AFC Defeat
Dual Double -Tuned Transformer
Coupled Limiters.
More than a year of research, planning and engineering went into the making of
the Lafayette Stereo Tuner. Its unique flexibility permits the reception of binaural
broadcasting (simultaneous transmission on both FM and AM), the independent
operation of both the FM and AM sections at the some time, and the ordinary
reception of either FM or AM. The AM and FM section, are separately tuned,
each with a separate 3-gong tuning condenser, separate flywheel tuning and
separate volume control for proper balancing when used for binaural programs.
Simplified °scum,. knife-edge tuning is provided by magic eye which operates
independently on FM and AM. Automatic frequency control "locks In" FM signal
permanently. Aside from its unique flexibility, this is, above all else, a quality
high- fidlity tuner incorporating features found exclusively In the highest priced
Sep
It
Dee
as a Hi
1
Stereophonie
FM-AM lamer
i.e
'
It as a Dna/FM-AM /nover
M
5'ee It
airtight
Mattanns/ FM or AM
r
S
timer
tuners.
FM specifications include grounded -grid triode low noise front end with triode
mixer, double-tuned dual limiters with Foster -Seeley discriminator, less than
harmonic distortion, frequency response 20-20,000 cps +- 'h db, full 200 kc
bandwidth and sensitivity of 2 microvolts for 30 db quieting with full limiting at
volt. AM specifications Include 3 stages of AVC, 10 kc whistle filter,
ic
built-in ferrite loop antenna, Ins than 1% harmonic distortion, sensitivity of 5
microvolts, 8 kc bandwidth and frequency response 20.5000 cps ± 3 db.
The 5 controls of the KT-500 are FM Volume, AM Volume, fM Toning, AM Tuning
and 5- position Function Selector Switch. Tastefully styled with gold-brass escutcheon having dark maroon background plus matching maroon knobs with gold
Inserts. The Lafayette Stereo Tuner was designed with the rbuilder in mind. Two
separate printed circuit boards make construction and wiring simple, even for
mplex unit. Complete kit includes all parts and metal cover, a step -bysuch q
step instruction manual. schematic and pictorial diagrams. Size Is
° W x
103/4" D x 4t/," H. Shpg. wt, 22'ibs.
ADVERTISING
INDEX
Acoustic Research, Inc.
American Concertone
Amperex Electronic Corp.
11
Apparatus Development Corporation
87
Arnhold Ceramics, Inc.
76
Audio Bookshelf
84
15
Audio Devices, Inc.
Audio Fidelity, Inc.
55. 57. 59, 61
Audiogersh Corp.
6
Bell Sound Division, Thompson Ramo
Wooldridge, Inc.
Bell Telephone Laboratories
British
1
KT
-500
74.50
7.45
IN
CNLY
100
KIT
FORM
IY/
KT -500
DOWN
MONTHLY
LT -50 Some as above, completely factory wired and Need
Net
Net
74.50
124.50
NEW! LAFAYETTE PROFESSIONAL STEREO
MASTER AUDIO CONTROL CENTER
Solves Every Stereo/Monaural Control Problemi
UNIQUE STEREO 8 MONAURAL CONTROL FEATURES
AMAZING NEW BRIDGE CIRCUITRY FOR VARIABLE
3d CHANNEL OUTPUT 8 CROSS -CHANNEL FEED
PRECISE
LA 600
WIRED
13450
"NULL" BALANCING
75
82
10
77
Allied Radio Corp.
Altec Lansing Corporation
Industries Corporation
facing p.
37
20
1.
3, 72
CBS -Hytron,
A Division of Columbia
Broadcasling System. Inc.
Classified
Components Corporation
Connoisseur
83
86
87
81
Doubleday G Co.
Durant Sound Co.
Dynaco Inc.
86
87
73
EICO
13
Cou. IV
Electro -Voice Inc.
Electra -Voice Sound Systems
87
81, 82, 85
Ercona Corporation
Fisher Radio Corporation
41
Fukuin Electric (Pioneer)
78
General Electric Company .. 31, 33, 35.
Glaser- Steers Corporation
Gotham Audio Sales Co., Inc.
Grado Laboratories
Coy
Gray Manufacturing Co., Inc.
Grommes, Div. of Precision Electronics
Inc.
47
51
78
I4
III
....
SYSTEM
A REVOLUTIONARY DEVELOPMENT IN STEREO HIGH FIDELITY. Provides such unusual
ual features aas a Bridge Control,
for variable cross -channel signal feed for elimination of "ping pang" (exaggerated separation) effects and for 3d channel
output volume control for 3- speaker stereo systems, 3d channel
output also serves for mix ing stereo to produce excellent manaural recordings. Also has full input mixing of monaural program
sources, special 'null" stereo balancing and calibrating system
(better than meters), 24 equalization positions, all- concentric
controls, rumble and scratch filters, loudness switch. Clutch type
olerme controls for balancing or as
Master Volume Control.
Has channel reverse, electronic phasing, input level controls.
Sensitivity 1.78 millivolts far
volt out. Dual lowimpedance
outputs (plate followers), 1300 ohms. Response 10- 25,000 cps
± 0.5 db. less than .03% IM distortion. Uses 7 new 7025 lowse dual triodes. Size 14" x 4''," x 10% ". Shpg. wt., 16 lbs.
Complete with printed circuit board, cage, profusely illustrated
instructions, all n
sary parts.
Harman Kardon
Heath Company
High Fidelity House-
79
45
7
-9
87
Institute of High Fidelity
71
Jensen Manufacturing Company
39
Key Electronics
Kierulff Sound Corporation
87
1
1
RESPONSE
10. 25,000
CPS
±
0.5
DB
6 CONCENTRIC FRONT PANEL CONTROLS
4 CONCENTRIC REAR PANEL
INPUT
LEVEL CONTROLS
180°
ELECTRONIC PHASE REVERSAL
NEW!.A LAFAYETTE
LAFAYETTE KT -600
LA -600 Same as above.
-
Stereo
wired
Preamplifier kit
.
Net
Net
79.50
134.50
STEREO /MONAURAL BASIC POWER AMPLIFIER KIT
29
74
49
80
Pickering Cr Company
Pilot Radio Corporation
Professional Directory
18
±
LESS THAN 1%
HARMONIC OR
INTERMODULATION DISTORTION
in easy-to-build kit form to save
amplifier,
P.
BOX 511
JAMAI CA 31, N. Y.
LAFAYETTE Catalog
590
CUT OUT
AND
ON
POSTCARD
PASTE
Address
City
Lansing, James B. Sound, Inc.
Leonard Radio. Inc.
Omega Stereophonic Disk
ORRadio Industries, Inc.
Name
I
87
88
North American Philips Co., Inc.
-
Send FREE
Lafayette Radio
RESPONSE BETTER THAN 35. 30,000
t/, DB AT IL WATTS
CPS
PRINTED CIRCUIT BOARDS FOR
NEAT, SIMPLIFIED WIRING
channel
a'e#e 1Qadia
56
Lacy's
2
Into stereo now at minimum expensel Dual
inputs are provided, each with individual volume control, and the unit may be
used with a stereo preamplifier, for 2 -18 watt stereo channels o
at the flick of
° a fine 36 -watt
w
monaural
m
ral amplifier
if desired, it r,may be used a
2 separate s monaural I8 welt amplifiers! CONTROLS include 2 input volume controls,
Reverse switch (AB -BA), Monaural- Stereo switch. DUAL OUTPUT
IMPEDANCES a e, 4, 8, 16 and 32 ohms (permitting parallel (monaural) operaton of 2 speaker systems of up to 16 ohms. INPUT SENSITIVITY is 0.45 volts per
channel for full output. TUBES are 2-6AN8, 4.7189; GZ -34 rectifier. SIZE 9-3/16"d
(10. 9/16" with controls) x SI/4"h x 131/4"w. Supplied complete with perforated
metal coge, oll necessary parts and detailed instructions. Shpg. wt., 22 lbs.
KT -310 Stereo Power Amplifier Kit
Net 47.50
V
87
Development Corpora-
OPTIONAL USE AS 36 -WATT
MONAURAL AMPLIFIER
EMPLOYS 4 NEW PREMIUMTYPE
7159 OUTPUT TUBES
A superbly-performing basic stereo
you lots of money and let you get
-
tion
6
36 -WATT STEREO AMPLIFIER15 -WATTS EACH CHANNEL
FOR
ONLY 4.75 DOWN
5.00 MONTHLY
KLH Research
4
53
87
Radio Corporation of America
Rigo Enterprises, Inc.
Roberts Electronics Inc.
Schober
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82
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Reslo
74
Organ Corp.
Sherwood Electronic Laboratories
Stromberg- Carlson. A Division of General
62 -69
Dynamics Corporation
1
Tandberg of America, Inc.
Tech -Master Corporation
Thorens
Truvox Ltd. (U.S.A.)
86
United Transformer Corp.
University Loudspeakers, Inc.
87
43
Vitavox
85
5
2
17
Zone.... State
AUDIO
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MARCH, 1959
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START YOUR HIGH FIDELITY SYSTEM
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HSK -33
$49.50
GRAY Custom DeLuxe turntable, arm and base
Factory assembled components
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33 H Hysteresis- Synchronous.
Turntable
$79.95
212 SP 12" arm
34.00
33 C Wood Base
23.95
GRAY Tone Arm Kit
Outstanding features such
as dual viscous damping,
GRAY Micro - Balanced Pressure Gauge
Indicates pressure on record
surface so that adjustments
can be made for proper
quick change cartridge
slide, adjustable static
tracking.
balance, and versatile wiring for all cartridges make this your best buy in a tone arm.
SAK -12 12" arm kit
$23.95
A
true balance
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PG
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$2.50
Visit your friendly quality Gray dealer for a full demonstration. Write to us for complete literature.
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Manufacturers of
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