the sound engineering magazine
THE SOUND ENGINEERING MAGAZINE
www.americanradiohistory.com
AUGUST 1977
$1.00
H ere's
how useful
a distortion analyzer
can be
Monitor soltare. power. dotortion or dB rato-
No manual
nulling controls required (the 1710A is ala null in less than 5 seconds).
Intermodulation Distortion Analyzer optionally available.
ways in auto -null, reaches
Oscillator distortion is typically .001 %.
±1
dB Vernier adds fine
level control.
Measure generator shoal at
load with the push of a
button.
Internal oscillator adjustable from +26 dBm to
-89.9 dBm
Selectable 18 dB per octave filters reject hum and
high frequency noise.
Turn off oscillator for quick
S/N measurement.
Tuning indicators help
measure distortion of an
Fast pushbutton operation
lets you set level, measure
voltage or power, then measure distortion.
Measure voltage or power
from lOHito110kHz
100
k2
Balanced Input.
in 0.1 dB steps.
external source.
Simultaneously select oscillator and analyzer frequency
with fast -to -use pushbuttons. 10 Hz to 110 kHz.
-
e
Balanced and floating 1502
or 6002 Generator output.
i
View input signal on a
scope.
Automatic Set Level is optonally available.
View distortion products on
a scope.
Two of the above features are so outstandingly
valuable that we especially invite your attention
to them.
One is the fast, easy measuring you get with
pushbutton -selected distortion-measuring circuits
(signal source and measuring circuits are simultaneously selected with the same pushbuttons).
Pushbuttons make it so simple to measure quickly
and to repeat measurements.
Secondly, you can drive virtually any type of
whether
circuit from the signal source output
-
®
Measure distortion down to .002%, voltage or S/N ratios
with 100 dB dynamic range.
balanced, unbalanced, off -ground or whatever.
That's because the signal source output circuit is
fully isolated and balanced.
There is no output transformer to introduce noise
or distortion.
Besides these outstanding conveniences, you
can have the Sound Tech 1710A with an option that
enables you to measure intermodulation distortion.
Call Mike Hogue /Larry Maguire to get full information on an instrument recognized everywhere
as the standard of the audio field.
SOUND TECHNOLOGY
1400 DELL AVENUE
CAMPBELL, CALIFORNIA 95008
(4081378-6540
Circle 10 on Reader Service Card
Coming
Next
Month
The subject is
0
DISC RECORDING.
PETER SKYE has
THE SOUND ENGINEERING MAGAZINE
submitted an ar-
AUGUST 1977 VOLUME 11, NUMBER
ticle that examines the need for and
ways of achieving disc center accuracy.
STAN RICKER of the JVC Cutting
Center in Los Angeles has written a
fully illustrated paper on half speed
cutting and makes a case for its more
extensive use.
GEORGE ALEXANDROVICH returns to
our pages with an article entitled The
Story of a Forgotten Stamper in which
he describes the development and application of a new stylus configuration
that can play a stamper or mother directly.
8
32
THE EQUALIZATION MYTH
Alan Fierstein
34
MUSIC ALFRESCO IN CENTRAL PARK
Martin Dickstein
38
db Test -BGW POWER AMPLIFIER
visited a major
New York disc mastering house and
has prepared a study of this important aspect of the audio business.
2
ADVERTISERS INDEX
4
CALENDAR
Coming in September in db, The
Sound Engineering Magazine.
8
BROADCAST SOUND
Patrick S. Finnegan
16
THEORY AND PRACTICE
Norman H. Crowhurst
22
THE SYNC TRACK
John M. Woram
24
SOUND WITH IMAGES
Martin Dickstein
26
NEW PRODUCTS AND SERVICES
41
CLASSIFIED
44
PEOPLE, PLACES. HAPPENINGS
CHARLES
REPKA
About
The
Cover
db is listed in Current Contents: Engineering and technology
Larry Zide
EDITOR -PUBLISHER
The cover is of a Grand "Robeyphone" manufactured by Charles T.
Robcy, Ltd. The exact date of manufacture is not known. There is an error in the photo. The disc on the platter is an Edison vertical cut, but the
Robeyphonc was designed only for
horizontal cuts. We want to thank the
Audio Technica Company in the U.S.
and Japan. The photo itself is by
SUSUMO ENDO and was taken in Japan.
Bob Laurie
ART DIRECTOR
Eloise Beach
CIRCULATION MANAGER
Ann Russell
ADVERTISING PRODUCTION
John M. Woram
ASSOCIATE EDITOR
Hazel Krantz
COPY EDITOR
Lydia Anderson
BOOK SALES
Crescent Art Service
GRAPHICS AND LAYOUT
db. the Sound Engineering Magazine is published monthly by Sagamore Publishing Company, Inc. Entire
contents copo right
1977 by Sagamore Publishing Co.. Inc.. 11 20 Old Country Road. Plainview. L.L. N.Y.
11803. Tekphonc (516) 433 6530. db is published for those individuals and firms in professional audio recording, broadcast. audio -visual. sound reinforcement. consultants. video recording. film sound. etc. Application should be made on the subscription form in the rear of each issue. Subscriptions arc 57.00 per year
($14.00 per year outside U.S. Possessions, Canada and Mexico) in U.S. funds. Single copies are $1.00 each.
Controlled circulation paid at Brattleboro, VT 05301. Editorial. Publishing. and Sales Offices: 1120 Old
Country Road. Plainview. New York 11803. Postmaster: Form 3579 should be sent to abuse address.
i
www.americanradiohistory.com
Ampex
9.
30
& 31
Audio Distributors
23
BTX
23
Clear -Com
Communications Co. . .
Community Light & Sound
Garner Industries
H -M Electronics
Ivie Electronics
13
.
27
18
7
Cover 4
JBL
K & L Pro Audio
Lexicon
Orban -Parasound .
Recording Supply Co.
SAE
Sennheiser
Showco
Shure Brothers
SME
Soundcraft
Sound Technology
Sound Workshop
Standard Tape Labs
Studer-Revox
Tara Audio
The Mix
UREI
Waters Manufacturing
White Instruments
Woram Audio
Yamaha
14
22
.
20
2
.
.
.
.
.
5. 19
22
15
4
Cover
3
11
8
17
Cover 2
21
10
3
24
.
21
6
18
12
26
19
sales offices
ness,
If you're after a bigger share of the recording busiwe've just mode things a lot easier for you.
Our new lower price tog significantly lowers the cost
of our Delta -T 102 Series Digital Delays putting them in
reach of those studios, that up till now, hove found this equipment beyond their budgets.
You get o lot for your money. Our 102 -S is the cleanest- sounding unir made. The most versatile. The most exciting to work with. You get two independent delay lines in
a single chassis. Couple them with our new VCO module and
you get special effects like you never hod before: vibrato.
doubling with time delay and pitch shift, time delay panning, doppler shift, and a whole lot more.
You can start with the basics, if you wish. and build
os you go- thanks to Delta -T's cost -saving modular design.
Our 102 -S bulletin hos the whole story. We'll send you our
new prices, application brochure, and a demo record. A note
on your letterhead brings you all four. Write today.
THE SOUND ENGINEERING MAGAZINE
New York
1120 Old Country Rd.
Plainview, N.Y. 11803 516 -433 -6530
Roy McDonald Associates, Inc.
Dallas
Stemmons Tower West, Suite 714
Dallas, Texas 75207 214 -637 -2444
Denver
3540 South Poplar St.
Denver, Colo. 80237 303 -758 -3325
Houston
3130 Southwest Freeway
Houston, Tex. 77006 713-529 -6711
Los Angeles
500 S. Virgil, Suite 360
Los Angeles, Cal. 90020 213-381 -6106
exicon
60 Turner Street, Waltham,
Massachusetts 02154
(617) 891-6790
Export agent Gotham Export Corporation, 741 Washing:on S:ee: Ne.'. 'r3n.. Ne:. York 10014
Circle 12 on Reader Service Card
www.americanradiohistory.com
Portland
2035 S. W. 58th Ave.
Portland, Ore. 97221 503- 292 -8521
San Francisco
Suite 265, 5801 Christie Ave.
Emeryville, Cal. 94608 415 -653 -2122
IRAND
OLE OPRy
FAMILY
REUNION
The most exciting
new recording combo
in Music City
Willi Studer's Revox family of tape recorders and components for the
audiophile has joined Willi Studer's family of professional audio equipment
to form Studer Revox America. Inc., in Nashville. Tennessee USA.
This provides all Revox audiophile and institutional users the obvious
benefits of factory direct sales and service enjoyed by professional studios
and broadcasters.
R EVOX
Studer Revox America. Inc.. 1819 Broadway. Nashville, Tenn. 37203 / (615) 329 -9576
Circle 16 on Reader Service Card
www.americanradiohistory.com
In Canada
Studer Revox Canada. Ltd. / (416) 423 -2831
AND NOW,
AWORD ABOUT OVERLOAD,
FROM SENNHEISER'S
MD p21:
calendar
AUGUST
22 -23 N.Y.U. Seminar on R &D Management. Contact: Ms. Heidi
Kaplan.
N.Y. Management
Center, 360 Lexington Ave.,
New York, N.Y. 10017. (212)
953 -7262.
27 -29 National Music & Sound Show.
Hilton Hotel, New York City.
Contact: Music Retailer, 50
Hunt St., Watertown, Ma.
02172. (617) 926-3770.
SEPTEMBER
12 -18
13 -15
20 -22
27 -29
16 -18
A lot of engineers are worried
about overload these days.
And no wonder: Rock groups.
Country groups. Jetports.
And other high program and
ambient sources make it more
necessary than ever for
microphones to be
overload -free as
well as accurate.
Like our tough
MD 421 cardioid
dynamic.
In this test with
a starter's pistol, we
measured an instantaneous sound -pressure
level of some 175 dB -well
beyond what any musical
instrument or voice can pro-
duce -while the oscillogram
measured no clipping or
ringing.
Whether you need a
microphone to capture transient sound like this pistol shot,
or "face the music" on
stage at 130+ dB in a
disco or recording
session, consider
our MD 421. You'll
discover its precise
cardioid directionality, rugged design
and wide, smooth
response are ideal for
rock -concert, recording
and broadcast applications.
The price won't overload
you either.
Outdoor test with Tektronix scope. set for 10V /division vertical. 01. tisec /div. horizontal:
22 cal starter's pistol mounted 15 cm from MD 421 measured pressure of 111.000 dynes /cm'
(175 dB SPL). Smooth. rounded scope trace indicates total lack of distortion.
NENNHEISER
ELECTRONIC CORPORATION
10 West 37th Street. New York 10018 (212) 239 -0190
Manufacturing Plant Bissennorl /Hannover West Germany
Circle 25 on Reader Service Card
26,27
International Audio Festival
and Fair. Olympia, London,
U.K. Contact: British Information Services, 845 Third Ave.,
New York, N.Y. 10022. (212)
752-8400.
Synergetic Seminar, Kansas
City, Mo. Contact: Don Davis.
Synergetic Audio Concepts,
P.O. Box 1134, Tustin, Ca.
92680. (714) 838 -2288.
Synergetic Seminar, Syracuse.
N.Y.
Synergetic Seminar. New York.
N.Y.
Consumer Hi -Fi Show. Sheraton Motor Inn, New York, N.Y.
Contact: Charles Ray, Communications Show Corp. 30 E.
42nd St., Suite 1620, New
York, N.Y. 10017. (212) 9867592.
Electronic Representatives Assoc. Show. Statler Hilton Hotel,
New York City. Contact: Gil
Miller c/o Gilbert E. Miller
Assoc. 375 N. Broadway,
Jericho, N.Y. 11753.
OCTOBER
Synergetic Seminar, Boston.
Mass. Contact: Don Davis.
Synergetic Audio Concepts.
P.O. Box 1134, Tustin, Ca.
92680. (914) 838 -2288.
18 -20 Synergetic
Audio
Seminar.
Philadelphia, Pa.
5 -9
Hobby Electronic Fair, O'Hare
Exposition Center. Chicago, Ill.
Contact: Industrial & Scientific
Conference Management, Inc..
222 W. Adams St.. Chicago,
III. 60606.
15 -19 Instrumentation - Automation
Conference. Philadelphia Civic
Center, Philadelphia. Pa. Contact: Instrument Society of
America, 400 Stanwix St.. Pittsburgh, Pa. 15222. (412) 2813171.
5 -7
(continued)
Introducing the 622
a Parametric
Equalizer with even better performance
and more cost -effectiveness than its
highly reliable predecessor. Improved
manufacturing efficiency and state -ofthe -art componentry help us provide
more for less money.
We've added a host of features important to you -the professional user.
The 622 now includes in /out switches
for each band, balanced inputs (with
transformer -balanced output optional),
extensive RF protection, and the latest
FET-input opamps which reduce transient intermodulation to the vanishing
point and which provide THD guaranteed less than 0.025%, 20- 20,000 Hz at
+ 18 dBm output. A 115/230 volt 50 -60
Hz AC power supply is now standard. A
new proprietary parametric bandpass
filter has been designed which virtually
eliminates the effects of control wear and
complements the notching capability of
.
.
.
our "constant -Q" design by enabling 40
dB notches to be consistently obtained.
The 622 is backed by an outstanding
quality control program, including the
use of burned -in, hermetically -sealed
IC's, and further burn -in procedures on
the entire equalizer. We know this is
important to you when your equalizer
doesn't fail in front of an arena audience
of 5,000 people ... or on the air in drive time ... or in the middle of a critical mix.
This combination of unbeatable performance and quality makes the 622 the
professional's choice.
Your Orban /Parasound dealer has all
the details. Write us for his name and a
brochure with the complete 622 story.
orbon/poreiound
680 Beach Street
San Francisco, CA 94109
(415) 673 -4544
U,
Circle 29 on Reader Service Card
calendar (cont.)
Sound Business Show (ERA
Consumer Products Div.) Rodger Young Ctr., Los Angeles.
Ca. Contact: Alan Gediman.
Marshank Sales (213) 559 -2591.
I6 -21 SMPTE Technical Conference
& Equipment Exhibit. Century
Plaza Hotel, Los Angeles, Ca.
Contact: SMPTE, 862 Scarsdale Ave.. Scarsdale. N.Y.
10583.
18 -20 Western Educational Society
for Telecommunications Conference. Harrah's Hotel, Reno.
Nevada. Contact: Wendell H.
Dodds, Radio -Television Ctr..
University of Nevada 89557.
25 -26 New York University R &D
Management Seminar. Chicago, Ill. Contact: Heidi Kaplan, New York Management
Center, 360 Lexington Ave.,
New York, N.Y. 10017. (212)
953 -7262.
11 -12
I
Son
of
LP. 3P.
NOVEMBER
The LA -4 Compressor/Limiter is another great UREI performer.
It offers advanced IC design, added features, and a lower price.
The LA -4's new electroluminescent light source, the heart of its
patented Electro- Optical attenuator, is an L.E.D. which will not
change or deteriorate with age. Compression ratios are adjustable
from a soft, smooth 2:1 compression through super tight sounding
20:1 limiting. The natural sounding RMS gain control action makes
it ideal for professional recording and re- recording. Half rack size.
Priced under $350.00.
Available from your UREI dealer.
LA -4
COMPRESSOR /LIMITER
o RATIO
O METER
w.
.
7
,
-
.
N
7
a
a
a
.
al
0
OUTPUT LEVEL
THRESHOLD
UNIVERSAL AUDIO
STEREO
[
Synergetic Seminar, Washington, D.C. Contact: Don Davis,
Synergetic Audio Concepts.
P.O. Box 1134, Tustin, Ca.
92680. (714) 838 -2288.
Dixie Electronics Representa2 -6
fives Convention. Boca Raton
Hotel & Club, Boca Raton.
Fla. Contact: Kimball P. Magee, Dixie Elec. Reps. Inc.
1611 Perimetter Center E.. Atlanta, Ga. 30346.
4 -7
Audio Engineering Society Convention and Show, Waldorf Astoria, New York, N.Y. Contact: A.E.S., 60 E. 42nd St..
Rm. 449, New York, N.Y.
10017. (212) 661 -8528.
7 -8
N.Y.U. R & D Seminar. Los
Angeles. Ca. Contact: Heidi
E. Kaplan. New York Management Center, 360 Lexington Ave., New York, N.Y.
10017. (212) 953 -7262.
IO Society of Broadcasting Engineers, N.Y. Chapter meeting.
WQXR Presentation Theater,
N.Y. Times Building, 230 W.
43rd St.. New York. N.Y. 7:30
p.m. (Cafeteria dinner available.) Speaker: Ron Simon.
Contact Tom Padwa.
14 -17 B &K Seminar, Acoustical Materials. Cleveland, Ohio. Contact: B &K Instruments, 5111
W. 64th St., Cleveland. Ohio
44142. (216) 267 -4800.
15 -17 Synergetic Seminar. Nashville.
Tenn. See above.
29- Synergetic Seminar. Orlando.
Dec. 1 Fla. See above.
2 -9
%
ON
POWER
0
ON
8460 San Fernando Road, Sun Valley, California 91352 (213) 767 -1000
Exclusive export agent: Gotham Export Corporation, New York
Circle 30 on Reader Service Card
1
Unplug it
with vie.
The built -in calibration microphone is
equalized to the IE-10A case to ensure
flatness. An external input is provided
for on -line signal monitoring and use
with other types of microphones.
From the equalization of rooms,
speakers and tape recorders to noise
analysis and sound pressure level testing, the IE -10A is an audio pro. Using
inexpensive accessories the IE -10A will
also measure amplifier power, voltage
and total harmonic distortion.
If you think our specifications are impressive ... you should check out the
prices! So get "unplugged" with an 1E10A. Ask us for a brochure, or see your
local Ivie dealer for a demonstration.
Ivie just eliminated the power line
cord on professional audio test equipment. Our state -of- the -art designs are
going portable. You can leave those
heavy boxes and their extension cords
in the office, because the new IE -10A
Audio Spectrum Analyzer puts audio
analysis in the palm of your hand.
The IE -10A is an extremely versatile
audio analyzer combining the power of
a sound level meter with that of an octave bandwidth spectrum analyzer.
Calibrated in both dB SPL and dBm,
the unit measures a broad variety of
signals quickly and accurately.
The IE -10A
Spec Briefs
Frequency Range 22Hz - 22KHz.
45 dB' on- screen" display range.
Ten octave channels w/160 LEDS.
Selectable 1, 2 or 3 dB resolution.
Calibrated 45 to 140 dB SPL (A or C).
Calibrated - 116 to +g dBm.
Rechargeable Nickel - Cadmium batteries.
Weight is 15 ozs. (430 gms).
For free literature and data, contact:
IVIE ELECTRONICS, INC.
500 West 1200 South
Orem, Utah 84057
(801) 224 -1800
Or return the reader service card.
..
-
complete audio analysis system
in the palm of your hand.
a
2
13210R4
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The Ivie family is growing with a powerful
new set of accessories. Pictured above is the
IE -20A Pink Noise Generator and the IE -15A
Harmonic Distortion Analyzer is shown below.
-I - -1t)
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Circle 37 on Reader Service Card
www.americanradiohistory.com
PATRICK S. FINNEGAN
Broadcast Sound
3009 +FD200
The FD200 is a new accessory from SME:
a fluid damping device which can be
fitted, easily and quickly, to any Series Il or
Series II Improved arm. The benefits of
fluid damping have long been known:
resistance to external shock, audibly
improved bass, and reduction of spurious
low frequencies; but these are not fully
realised when the damping is applied at the
bearings. For this reason the FD200 is
designed to be fitted at a point along the
length of the arm.
The FD200 design overcomes the usual
problems of leakage and low efficiency. It
offers a choice of three damping rates, to
suit a wide range of cartridge compliances.
The attractively presented kit includes
viscous fluid and full instructions.
.
ririri
ri
'trritatuiti
ri
SHURE V 15 Type
15
MOWN
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ti
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5
6
7 a 910
DAMPED
15
20
Hz
- --- - UNDAMPED
The illustration shows the extreme low frequency response characteristics of a typical
high- quality cartridge in the Series ll
Improved arm.
Note the substantial reduction in the Q
of the low frequency resonance. A /though
these frequencies are themselves outside
the range of human hearing they give rise
to undesirable side - effects which are
audible.
Write to Dept 1 B43B, SME Limited
Steyning, Sussex, B N4 3GY, England
Exclusive distributors for the U.S.'
Shure Brothers Incorporated
222 Hartrey Avenue
Evanston, Illinois 60204
and in Canada:
A. C. Simmonds and Sons Ltd
975 Dillingham Road
Pickering, Ontario, L1 W 3B2
i
t
r
co
Stereo Monitoring
and Measurements
The stereo modulation monitor provides a considerable number of measurement functions in addition to its
monitoring functions. But the stereo
signal is more complicated than a
monaural signal and requires more
measurements to determine its overall
quality. To produce accurate results.
the monitor must be kept in good repair, calibrated, and correct procedures must be used in making the
measurements. The instruction manual
for the particular model will provide
detailed instructions for the adjustments required for calibration, as well
as procedures to use for measurements. We don't have space here to
go into all the various procedures for
specific models. but 1 will try to point
out some of the important test areas
and what the instrument measures at
those times.
METERING
Except for distortion measurements,
most monitors can measure just about
every important parameter needed to
determine the system's transmission
quality.
The monitor will contain at least
two wideband, a.c. voltmeter sections.
The inputs to these meters are on a
selector switch so that the desired
parameter to be measured can be selected. There will also be a sideband
amplifier and a precision attenuator
that is switched into the circuit path
of the selected meter so that very
small amplitude parameters can be
measured with the meter section.
The panel meters themselves will
have a scale similar to that of a vu
meter or a modulation meter scale.
This will be a 0 -133 per cent range
and a dB scale (the 100 per cent and
zero dB coinciding). One of the meters
will have another scale in percentage
for measuring the pilot signal. The
basic calibration is such that for a
given internal voltage (according to
the monitor's design), the meter will
Circle 17 on Reader Service Card
www.americanradiohistory.com
SIGNAL
PARAMETERS
y--.
SPECIAL
AMPLIFIER
«
-+
INPUT
SELECTOR
SWITCH
METER
SELECTOR
SWITCH
ATTENUATOR
-o
METER
RECTI FIER
PANEL
METER
Figure 1. The metering section is a
precision. wideband a.c. voltmeter.
indicate 100 per cent (zero dB). For
measurement of low level parameters.
the parameter voltage is amplified in a
special amplifier and then attenuated
with a precision attenuator. This raises
the voltage to an amplitude that can
he indicated on the meter and the
calibrated attenuator and meter will
then indicate the actual level in dBs.
During programming, both meters
usually remain in the program's left
and right audio channels so that the
audio levels of these two channels can
be continuously monitored.
38 kHz PHASING
Stereo monitoring functions and
some of the measurement functions
require current phasing for accurate
results. This is due to the fact that the
monitor reconstructs a 38 kHz subcarrier from the incoming 19 kHz
pilot. Because the reconstructed subcarrier is used in the demodulation
process for recovering the L-R audio
information contained in the side bands of the original subcarrier, the
new subcarrier must have the sanie
phase as the original subcarrier which
it is replacing.
The 19 kHz pilot is derived from
the original subcarrier's oscillator and
thus has the same phase: theoretically
Technof
¡cal
Leader
Ampex, headquartered on the San Francisco Peninsula, is the company that "invented" the magnetic recording industry.
or!p3
technology pioneered by Ampex
over three decades has affected many
aspects of our modern lifestyles, and
has established Ampex as a leader in
magnetic recording. Our continued effort in developing new technology has
always been the key to our leadership. Right now
our Advanced Technology, Data Products and
Audio -Video Systems Divisions are embarking on
several new programs. To insure the success of
these programs we are seeking innovative
graduate engineers with experience in the fields
listed below.
Opportunities like this don't happen very often. But
they're happening at Ampex now
The
Advanced Technology
cades!
disk read /write systems and equalizing systems
for tape recorders
codes for magnetic recording
precision servo systems for both linear positioners and rotating systems
mechanical design of high precision systems in
disk recorders and in longitudinal, helical and
transverse scan tape recorders
Audio -Video Systems
Division
analog videotape signal systems
digital video signal processing
Division
electron beam and optical recording
magnetic recording
tape or film handling
servo systems
videotape editing
professional audio recorders
head technology
TV cameras
servos
high -bit rate digital circuit design
optics
signal analysis
pattern recognition
high frequency circuit
communications theory
in
Data Products Division
circuit /systems design of very high -bit rate
systems
Manager Corporate Staffing
Corporation
AMPEX
Building 2, 2655 Bay Road
Redwood City, CA 94063
Dept.
you think you have something valuable to offer
any of these or closely related areas, and if you
would like to join some of America's most talented
engineers, please send your resume or a letter outlining your qualifications to: Ampex Corporation,
ATTN: Corporate Staffing Manager, Building 2,
2655 Bay Road, Redwood City, CA 94063. Or you
can send us this coupon and we'll get back to
you. We are an equal opportunity employer m /f.
If
Occupation
Years of Experience
Employer
1
Name
Address
City, State, Zip
Phone
AMPEX
CD
www.americanradiohistory.com
the reconstructed 38 kHz subcarrier
should have an identical phase as the
pilot. Since in the reconstruction process there can he phase variances, the
new subcarrier must have its phase
adjusted to that of the pilot. Some
monitors use a phase -lock loop for
control of this phase. Others use a
RECONSTRUCTED
SUB- CARRIER
- -T+
38 kHz SIDEBAND
COMPONENTS
--
LEFT
AUDIO
IT
-To
1i
OUT
RIGHT
AUDIO
(A)
DETECTOR
TURN ON
TURN OFF
SUB- CARRIER
Figure 2. The
reconstructed
sub -carrier must
be exactly in
TURN ON- OFF
+ NORMAL
phase with the
sideband signal or
the results will be
wrong. At (A)
correct phase, at
(B) incorrect
phase.
+
SIDEBANDS
-
LEFT
o
NORMAL
-1--
(B)
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o
Circle 13 on Reader Service Card
-
RIGHT
manual adjustment.
Since monitoring and measurement
results rely upon correct phasing, the
phase should he checked and verified
during programming, and especially
before making a series of measurements.
PHASING AND SIDEBANDS
The phasing adjustment in the
monitor adjusts the phase of the reconstructed 38 kHz subcarrier to that
of the pilot. This assumes that the
pilot still has the correct phase relationship to the sidebands as it did in
the stereo generator. If anything should
happen during the transmission to
change this phase relationship, for example. a distorted bandpass, or a fault
in the stereo generator. or misadjust-
ment of the generator, then of course
the new subcarrier will not have the
correct phase relationship to the side bands. This is one of those situations
where the standard is not a true standard anymore. Whatever the reason.
the reconstructed subcarrier must have
the correct phase relationship to the
sidebands-this is where the action
takes place!
PHASING ACTION
Correct phasing results in accurate
recovery of the audio contained in
the subcarrier sidebands. For functions requiring that audio, phasing
must be accurate. Incorrect phasing
will cause incorrect demodulation of
the sideband audio. When this is mat rixed with the SUM component, the
left and right audio output signals
will not be the same as they were
when they went into the system.
Perfect phasing will align each cycle of the reconstructed subcarrier
with each cycle of the sideband signal so that the peak of each of these
signals will occur at exactly the same
instant (and in correct polarity). Because the subcarrier amplitude will be
many times greater than that of the
sideband signal, it will control the action of the stereo detector. As the 38
kHz cycle goes in the positive direction, for example, the detector will
begin to conduct as soon as this voltage reaches the forward conduction
threshold, and it will remain in conduction until the subcarrier voltage
drops below that point again. During
this on time of the detector. sideband
voltage will be allowed to pass to the
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TECHNICORNER
The M615 Analyzer's display contains
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A rotary hi /lo envelope control adjusts
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the resulting frequency response is
correct within ± 1 dB. Includes input
and microphone preamplifier overload
LEDs. A front panel switch selects
either flat or "house curve"
equalization.
The ES615 Omnidirectional Analyzer
Microphone (also available separately!
is designed specifically for equalization
analyzer systems.
FI
SF--HIJ I=t E
e
MANUFACTURERS OF HIGH FIDELITY COMPONENTS, MICROPHONES, SOUND SYSTEMS AND RELATED CIRCUITRY.
Circle 14 on Reader Service Card
www.americanradiohistory.com
of the audio in one channel will find
MONITOR LEFT
AUDIO CHANNEL
MONITOR RIGHT
AUDIO CHANNEL
its way into the other channel by various means. The monitor will measure
the residual audio in one audio channel
that belongs in the other channel. But
ti
SELECTOR
SWITCH
Figure 3. Meters
read the ratio of
the voltage
amplitudes in both
audio channels
for separation
measurements.
(Shown is lef t-toright separation.)
METER
RECT
PANEL
METER
dB SEPARATION
detector's output ports. The actual
peak amplitude of this sideband voltage depends upon where the sideband
cycle is in relation to the phase of
the subcarrier cycle. If the 38 kHz
leads or lags the phase of the sideband, conduction will be either on the
up slope or the down slope of the
sideband cycle. Therefore, the actual
peak voltage reached in the detector
output circuit depends upon the sideband amplitude at this point in timcit will be less than the sideband true
peak value. If the 38 kHz should lead
or lag by 180 degrees. the positive
half -cycle would cause the detector to
conduct on the negative half-cycle of
the sideband, reversing the left and
the right output audio channels!
SEPARATION
An important measurement of the
system is the separation of the left
and right audio channels. Perfect separation requires that each of these
channels retain its identity throughout
the system. If there is audio in one
channel. then ideally none of that
audio should appear in the other channel, But no system is perfect and some
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Octave equalizer
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the monitor cannot measure separation
with program signal since both audio
channels are active and there would
also he no reference.
In the normal measurement procedure. an audio sine wave is fed to
one channel of the stereo generator
and the other channel remains idle.
The level of this signal is the normal
full channel input level and the composite signal will modulate the f.m.
carrier to 100 per cent. If the audio
is fed to the left channel for example.
then the left channel meter on the
monitor will indicate to 100 percent
(zero dB), and the right meter will
indicate nothing. Since the separation
measurement is a ratio of the audio
signals that now appear in both channels, the audio in the left channel (in
this case) must be at the zero dB
(100 per cent) level. The amplitude
of the residual signal appearing in the
right audio channel will then be so
many dB below this left channel
level.
Now that the unit is set up to measure the separation. the special amplifier /attenuator is switched into the
right circuit path so that the right
meter can now indicate the actual dB
level of this residual signal. The meter
and the attenuator will then provide
a direct reading in dBs of the left -toright channel separation. To measure
separation in the other direction, that
is, right -to -left, the right audio channel is fed tone and the metering
switched to indicate the residual in
the left channel caused by the right
channel audio.
Accurate separation measurements
depend upon an accurately calibrated
monitor. Before making a series of
measurements. the monitor's own separation should be checked out and
calibrated according to the instructions in the instruction manual. The
internal separation in today's monitors is something like 70 dB.
CROSSTALK
Crosstalk in the stereo measurement sense is the measurement of signal components that appear in the main
channel (0 -15 kHz band) or in the
sub- channel region (23 -53 kHz band)
when there is modulation of one or
the other area separately. In programming, of course. both of these two
areas of the composite signal are active and modulating the f.m. carrier.
but for measurement purposes. only
one area is activated at a time while
the other area is measured. To cause
this to happen requires the correct
input to the stereo generator. To oh-
At first
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Which is understandable. They are.
It's quite plain that these are not
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All of our enclosures are of a solid
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The PBL,
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Community Light & Sound Inc., 5701 Grays Avenue, Phi adelphia
Circle 28 on Reader Service Card
www.americanradiohistory.com
PA 19143
(215) 727-0900
w
r---1
n
DET
L___J
V
Figure 4. Filters
select the part of
the bandpass
section for
crosstalk
measurements.
Shown here is
main -intosubchannel
crosstalk.
tain
ONLY)
ICOMP
FM
1
L+R
(SUM
8PF
23-z31
k
Hz
II
/'1.
ATTI--.
AMP
-
METER
REGT
ii
dB
main -channel -only
modulation.
the audio to the left and right inputs
of the stereo generator must be inphase sine waves. The output of the
generator will then be only a SUM
audio signal-with no sub- carrier side bands at all. To obtain sub- channel
modulation, the audio must be fed to
both inputs of the stereo generator
out -of- phase. The output then is only
that of sub -carrier sidebands, with no
SUM signal.
Whichever measurement is to be
made, with the appropriate input to
the stereo generator, for example, the
main channel. the sub- channel arca of
CROSS
-TALK
the spectrum is passed by an accurate
filter and any signal components present are measured by the metering circuit in dBs. This is crosstalk main into
sub -channel. For sub into main, the
other condition is set up and the audio
band is selected by an accurate lowpass filter, fed to the metering circuit.
and measured in a similar manner.
High or out -of- tolerance crosstalk
measurements can be caused by the
filters in the monitor, filters in the
stereo generator, or by harmonics and
intermodulation components caused
by non -linear operation somewhere in
the system.
38 kHz SUPPRESSION
The carrier in a.m. modulation contains no intelligence information, and
in our stereo multiplex, the carrier is
suppressed. This conserves the modulation capability of the f.m. carrier.
Any subcarrier that is present in the
composite signal will add to the amplitude of that signal and thus would
require reducing the f.m. carrier modulation. If, for example. there is a
fault or misadjustment in the stereo
generator so that 10 per cent of the
composite signal is subcarrier, to prevent overmodulating the f.m. carrier.
the modulation must be reduced 10
per cent (1 dB). We have already
lost IO per cent to the pilot and if
sea is in use. another 10 per cent.
This would leave only 70 per cent of
SIDEBANDS ONLY
(A)
10
THE
CUE MACHINE
%
SIDEBANDS + 10 %
SUB- CARRIER
(B)
Figure 5. Any signal of the original
sub -carrier that is not suppressed will
add to the amplitude of the composite
signal. (10 per cent shown here.) At (A)
normal carrier suppression is shown
while at (B) can be seen 10 per cent of
sub carrier in the signal.
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Circle 31 on Reader Service Card
www.americanradiohistory.com
the modulation to our audio signal.
and signal -to -noise in the audio suffers. A narrow 38 kHz pass filter will
direct any incoming 38 kHz to the
metering section for measurement.
This must be down at least 40 dB.
SUMMARY
The stereo monitor offers many test
capabilities as well as monitoring facilities. By learning how the particular monitor operates and what it is
measuring, the station engineer will
find the monitor very helpful in defining problems and make troubleshooting and corrections easier.
Circle 35 on Reader Service Card
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SAE's goal today, just as it has been for
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as a testament to this goal.
-
First, their design all SAE amplifiers have
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design approach, not only the output (as in
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This ensures low transient and steady -state
distortion, plus full stability and fast overload recovery. Combine this with our high
slew rate for accurate transient response,
feedback gain controls which will not
degridate the input signal (2600, 2400L), and
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The result is state -of- the -art performance,
but to realize this performance we must have
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In order to ensure optimum performance
from these unique design concepts, SAE
retains total control over the manufacture,
selection, and assembly processes. We maintain 40,000 sq. ft. of production area where
the latest techniques in metal and circuit
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NORMAN
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CROWHURST
theory & Practice
Use of Analogs: part 2
Last month I left you with a problem that is a useful half -way introduction to the use of analogs. I finished
up showing you the physical dimensions that determine leakage inductance between windings, without considering how you will represent such
an inductance in a schematic. This is
where it gets into a kind of analog
situation.
I did point out something that has
been argued from time to time. that
leakage inductance is highly linear because it is effectively an "air- cored"
inductance even on an iron -cored
transformer, unless you go to the trouble of inserting magnetic material in
the leakage path -which is unusual
but has been done.
FIGURE 3 of last month's article
indicated that most winding spaces are
longer than they arc deep. FIGURE
repeats that sketch. with an additional
one to illustrate the point. If the space
occupied by the windings is approximately three times as long as it is deep
and if it is totally occupied by two
windings, a primary and a secondary.
what will he the comparative leakage
inductances between the two windings. arranged in the alternative manners shown?
Because the roles of the dimensions
identified as L1. and D are interchanged. the leakage inductance, assuming the same number of turns in
each arrangement will he approximately nine times the value, in the arrangement on the right, of that on the
left. And, like the primary form of
inductance, its value is proportional
to the square on the number of turns
in the winding.
Suppose one winding has 1,000
turns, and the other one has 1,500
turns, what does that mean? All right.
suppose that, in the arrangement on
the left, the leakage inductance referred to the 1,000 -turn winding is 10
millihenries. Then, referred to the
1,500 -turn winding, it will be 1.5
squared, or 2.25 times this, which is
22.5 millihenries.
Now, going to the arrangement at
the right, referred to the 1,000 -turn
winding, the leakage inductance will
1
he nine times the value, or 90 millihenries. Referred to the 1500 -turn
winding, it will he 202.5 millihenries.
CAPACITOR ACROSS THE
WINDING
Nett, as a step toward designing
the filter I introduced at the end of
last month's column, what would be
the effect of connecting a capacitor
across the 1,500-turn winding, say a
0.01 microfarad value? This depends
on where you look at the circuit. Let
us take the arrangement on the right
because that most nearly corresponds
with the arrangement we shall use
to design the filter.
A capacitor of 0.01 microfarad will
tune an inductance of 202.5 millihenries to about 3,500 hertz. Looked at
through the transformer, the capacitor
will have its reactance divided by
2.25 or its capacitance value multiplied by 2.25 to look like a value of
0.0225 from the 1000-turn side. So
from that side, it looks like 90 millihenries with 0.0225 microfarad, which
also tunes to about 3,500 hertz.
FIGURE 2 shows how the circuit will
look with external impedance components. On the secondary, or 1,500 -turn
side, the capacitor is in parallel with
any other load impedance connected.
But on the primary, or 1,000 -turn side.
Figure 1. Two
ways of disposing
of leakage
inductance within
a transformer
winding.
the leakage inductance and capacitance are in series.
This means that if the impedance
on the 1,000-turn side is very low in
value, and the impedance on the
1,500 -turn side is very high except for
the 0.01 microfarad capacitor, the
equivalent circuit looks like a seriesresonant circuit from the 1,000-turn
side and a parallel- resonant circuit
from the 1,500 -turn side. The Q -value
of the resonance will increase by making the impedance on the 1,000 -turn
side lower and by making the impedance on the 1,500 -turn side higher.
The fact is that this arrangement
can act as a resonant, as well as an
ordinary, transformer in the same
package. The "operative impedance"
of the resonant transformer will be
V L /C, which figures to 2,000 ohms on
the 1,000-turn side, or 4,500 ohms on
the 1,500 -turn side. What this means
is that at the resonant frequency, putting 200 ohms on the primary will
look like 45,000 ohms on the secondary, or vice versa.
At that frequency, a 200 -ohm resistance on the 1.000 -turn side will
provide a maximum -energy transfer
match for a 45,000-ohm resistance on
the 1,500-turn side. Change the resistance on the 1,500 -turn side to
22,500 ohms, half the previous value,
and the matching resistor on the
1,000 -turn side will be double the previous value, or 400 ohms.
BUILDING A FILTER
When building the filter shown at
FIGURE 3, which was mentioned at
the end of last month's column, each
of the inductors can be a leakage inductance. FIGURE 4 shows a possible
physical configuration in cross-section.
The first inductance, L, in FIGURE 3.
can be the leakage inductance between section A and section B of FIGURE 4. The second inductance, L, in
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Soundcraft Nortf Americo Division
P.O. Box 883 JFK Station Jamaica NewYork 11430 USA
Telephone (212) 528 8158 Telex 01 -2203
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v1000
11
Figure 2. Circuit and equivalent circuit
of leakage inductance, tuned with a
capacitance.
FIGURE 3, can be the leakage
tance between section B and
C of FIGURE 4.
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Take a Waters
slim -line
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New MM thin -line faders are
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So across section C you connect
capacitor C,. One advantage of this
kind of design is that you make the
turns in section C suitable for using
some convenient standard value for
just as the 1,000 to 1,500 turns
ratio transformed the effective value
of the capacitor connected across the
second winding. Nothing but the capacitor is connected across section C.
Now, the relative widths of spaces
A and C in conjunction with the one
common to both, section B, determine
the relative values of L, and L_. In
practice what you do to design this
part of the circuit is to arrange spaces
A, B and C, so that the leakage inductances are in the ratio determined
by the theoretical design. You then
pick the number of turns on section A
to suit the designed input impedance
and the number of turns on section C
to suit the capacitor value you intend
to use as standard.
Now we have two inductors and a
capacitor of the filter. Winding B provides the output point for connecting
to the other elements, for which we
use spaces D, E. and F, which have to
be equal in their total to the total of
A, B, and C, as a matter of physical
convenience.
We make the spaces D, E, and F
to suit the ratio between the remaining two inductances, D to E, making
L, and E to F, making L,. Now what
we have to do is make the two sets fit.
As sections A, B, and C are on a different core limb from sections D, E.
and F, windings B and D may need
to have different numbers of turns.
The coupling is achieved by connecting the two windings together.
The difference in the number of
turns will arrange that the total space
A + B + C is equal to the total space
D + E + F when the relationship between inductances L, and
and L3
C
L
Figure 3. The filter circuit for which
leakage inductance is to be used. (See
text to find out how values are realized.)
L4
L3
Li
L2
WATERS MANUFACTURING,INC.
LONGFELLOW CENTER, WAYLAND. MA 01778
Circle 15 on Reader Service Card
inducsection
TC2
Another Limiter?
So ask the cynics. That's why we made the Orban /Parasound 418A special. It's a stereo compressor/limiter/highfrequency limiter system that compresses the dynamic
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cleaner than most linear amplifiers (THD at 1 kHz is
typically 0.02% for any degree of gain reduction), and
stereo tracking is locked -in for life without adjustments.
The 418A is highly "smart" and automatic. There are
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The Orban /Parasound 418A isn't "just another
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orbon/paroround
680 Beach Street, San Francisco, CA 94109
(415) 673 -4544
EIIIM
Circle 20 on Reader Service Card
.2Vaitie,afraxaotreseA.
Conquer distortion, defeat clipping,
clean up your mix.
Bi- amplificat on or tri- amplification
with Yamaha's F-1030 frequency dividing network can take you a long
way down the road to audio perfection
By separating high, mid and low
frequencies before amplification, the
F -1030 increases efficiency and headroom to the point where you need
fewer amplifiers and speakers to produce the some sound level. What's
more, by dividing the sound for several
amplifiers and many sets of speakers,
the F -1030 eliminates the cost of
individual passive crossovers.
Control your own! Unlike other
dividing networks, Yamaha's F -1030 offers
dB- calibrated detented controls on
both inputs and outputs, as well as transformer- coupled XLR and standard
phone jack connectors. Twelve selectable crossover frequencies range
from 250Hz to 8kHz. with your choice of
12dB /octave or 18dB octave slopes.
plus a switchable 40Hz 12dB/ octave high -
There's just not enough room here
to give you the whole story So send this
ad along with three dollars. (Please,
certified check or money order only.
No cash or personal checks.) We'll
rush you the F -1030 operation manual.
Or better yet. see your Yamaha dealer.
.
YAMAHA
pass filter.
confidence! Noise and
distortion are virtually extinct. The
Yamaha F -1030 will drive a full +24dBm
(12.3 volt) output into a 600 ohm load.
ft will also accept input levels to +30dB.
Use with
Circle 22 on Reader Service Card
Musical Instrument Combo Division
6600 Orangethorpe Avenue.
Buena Park. CA 90620
Write:
P
O. Box 6600. Buena Park. CA 90622
and L,. is satisfied. The turns on space
E are designed to suit the standard
capacitor used for C. in the same way
used for section C.
At this point we have a complete
filter which will match any convenient
values of capacitor, to the required
design values, and will also match different input and output impedances,
something that is not possible with
any other way of constructing this
kind of low pass filter.
REVIEW
If you are not sure how that worked,
go over it again carefully. The relationship between the first two inductors is fixed by the relative spaces, A.
B, and C. Their effective value is fixed
by the turns used on A. The relationship between the second two inductors
is fixed by the relative spaces, D, E.
and F. Their effective value is fixed
by the turns in D, relative to the turns
in B. Any sets of turns in the correct
ratio, which will not usually be far
from equal. will serve here, just changing the voltage at which the transfer
is made. For example, if the required
ratio proves to be 1.15, you could use
1,000 turns on B and 1,150 turns on
D. or 2,000 turns on B with 2.300
turns on D equally well.
IN
C2
CI
Figure 4. Physical
configuration of
windings to
achieve a filter
circuit.
E
B
C2
Finally, the relationship between the
effective values of the capacitors, and
the value actually used can be adjusted by the number of turns wound
in spaces C and E while the output
impedance can be adjusted by changing the turns of F.
This is a very interesting design procedure, and provides intriguing possibilities as a practical matter for iso-
audio
inventory
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www.americanradiohistory.com
lation of the various circuits, not possible with any ordinary low pass filter.
TWO TRANSFORMERS
Where is the trick, you may he
asking? Well, of course, any transformer also performs a high -pass
function as well as a low -pass function. This is really two transformers.
using a common core. Because you
use two legs of the same core, each
leg will have its own primary inductance, and thus you have two inductances that I have not talked about
so far.
These inductances have magnetic
cores. which the leakage inductances
we have been talking about do not. If
they should saturate anywhere in the
pass band. below the low -pass cut-off
frequency, they could introduce distortion. Or if. in conjunction with the
circuit impedances. these inductances
produce a high -pass action or low -frequency loss within the desired pass
band, that could detract from your
intended performance.
So you really do not get something
for nothing. But the use of leakage
inductances. which have physically
controlled values based on the dimensions of the structure. are highly
stable. and possess considerably better
Q values than simple air -cored types.
can be quite attractive. By being inside the core. although using air
spaces, they are effectively shielded
from outside fields, which air -cored
inductors are not. unless you put them
in a shielding can. which both changes
their values and downgrades their Q.
Candidly, I believe the only reason
that leakage inductance has not been
used more in equipment design is that
few engineers have figured out how
to put it to use, rather than having
to "fight" it as a source of high frequency losses.
Introducing
Norther California
Edition
THE MIX -the first comprehensive directory of commercial recording studios and services, Northern California edition.
THE MIX-will provide a reference guide for professional and
semi-professional recording studios and their clients.
THE MIX-over 100 studios [4 track and up] profiled in depth with a
complete and detailed description of pertinent information.
THE MIX-includes location. owners, engineers, dimensions of
control room and studio, number of tracks. types of tape recorders,
mixing consoles, monitor amps and speakers, outboard equipment,
microphones, instruments available, extra facilities, rates. credits.
history and direction.
THE MIX is being published with the cooperation and sponsorship
of some ofthe people who make it all happen in the Bay Area Music
Scene: Guitar Showcase, NARAS, Sound Genesis, HUN Sound,
Bananas at Large, Recording Specialities, David Rubinson and Different Fur.
r-
1
Send for your special bound edition today.
Please send
copies of THE MIX at
$5.00 +$1.25 postage & handling.
_
Name
Company Name
Address
City
Zip
State
A BAM
Magazine Publication
Southern California edition available soon.
weeks for delivery.
Send to: The Mix Magazine
PO Box 6395
Berkeley. Ca 94706
Allow
2 -4
Sound Workshop will introduce
its new 16 Track Recording console
at the Audio Engineering Society Convention
in New York City
on November 4th, Sth, 6th, and 7th.
We suggest you check
Sound Workshop
PROFESSIONAL AUDIO PRODUCTS
it out.
bringing the technology
within everyone's reach.
Sound Workshop Professional Audio Products. Inc.. 1040 Northern Blvd.. Roslyn. New York 11576 (516)- 621 -6710
www.americanradiohistory.com
fU
audio Tape
for professionals
JOHN M. WORAM
4a The sync Wack
Quad Sound and
Docket 21310
REEL TO REEL TAPE
Ampex. 3M. All grades,
On reels or hubs.
CASSETTES, C- 10 -C -90,
with Agfa. Ampex. 3M Tape
LEADER & SPLICING TAPE
j
-
D
EMPTY REELS & BOXES
All widths, sizes.
COMPETITIVE
FROM STOCK
-
Recording Supply Co.
1233 Rand Road
Des Plaines, IL 60016
of
Polyline Corp.
312/297 -095
Circle 36 on Reader Service Card
MEASURE
REVERB TIME
IN REAL TIME.
Instantly!
RT -60.
This easy -to -use
instrument delivers precise reverb time measurement in instant real time digital readout. No more chart recorder or time -consuming chart recorder analysis. The RT-B0's integrated circuitry incorporates a one -third octave band pass filter system with frequency centers on 250.500.1000.2.000. and 4.000 Hz. It
operates on self-contained ni -cad batteries. Mounted !n a
rugged carrying case. the RT -60 weighs only 3.5 pounds.
The dealer net cost. FOB San Diego. is lust
Write for your free technical
bulletin on the RT -60
instantly!
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communicATions
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11
Circle 32 on Reader Service Card
If you've dropped into your local
hi -fi emporium lately, you may have
discovered that inquiries about quad riphonic sound are about as welcome
as killer bees. I may be overreacting,
but it seems that the hardware retailer
takes great delight in doing what he
can to destroy whatever market there
is for quad. Since I'm involved (as a
consultant) in the quad scene, I hear
countless tales of would -be customers
being turned off by negative remarks
from the sales people.
Now although this magazine is presumably not identified as a hi -fi book,
we're all involved in hi -fi sooner or
later. After all, that's what the dB (and
db) is eventually all about, isn't it?
In the recording business, most of
us take stereo for granted, and plan
our recordings in terms of an eventual
left -to -right speaker placement. But if
and when quad sound firmly establishes itself, we shall find ourselves recording and mixing for four speakers
instead of two. Will we one day take
quad for granted too?
Assuming the ideal quad system exists, the creative possibilities are obvious. Ambience -type recordings create
a sense of spaciousness that is only
hinted at in stereo. Surround -sound recordings give the pop group a creative
tool that will keep an imaginative producer busy for hours. (Just think of
the studio rentals!)
But meanwhile, back at the hi -fi
shop, the salesman is doing his best to
steer the customer away from quad.
The hardware manufacturer is slowing
up his quad production line, because
of poor sales. Likewise, the record
manufacturer. who complains that
quad records don't sell very well.
(Ironically, the handful of stores that
are aggressively promoting quad seem
to be doing quite well. The big complaint is that they can't get enough
hardware and software to keep up with
the demand!)
Mr. Average Record Buyer is con-
fused. There are several systems competing for his attention. But who buys,
records according to "the system "?
Most of us buy them because of the
music. and if the competitive rivalry
means that our favorite artists are
spread out over two or three different
systems, we're apt to get discouraged.
and stick with good old safe stereo.
Presumably, once quad gets "off the
ground" the compatibility problems
will be solved in the marketplace. In
the meantime, the same folks who
used to say that "mono's all we really
need" are now piously chronicaling the
death of quad. One hopes that this
backward -looking mentality will eventually die by itself, but in the meantime,
quad sound is having a rough go of it.
THE FEDERAL COMMUNICATIONS
COMMISSION
And now, enter the FCC. According
to a recent news release. "The Cornmission has begun an inquiry on
whether to adopt standards for FM
quadriphonic radio broadcasting.
"The Commission said the purpose
of its inquiry was to determine whether
there was sufficient public and industry
interest to warrant adoption of standards for quadriphonic broadcasting.
and, if so, to develop a record that
would assist the FCC in formulating
standards.
"The Commission urged radio equipment manufacturers, broadcasters. and
the listening public to make known
their interests and to contribute relevant information to assist it in this
proceeding."
What does this mean to the average
db reader? Let's assume that most of
us are not radio equipment manufac-
turers or owners of broadcasting stations. (How's that for a safe bet ?) But
most of us are members of the listening public, and we have a more -thanroutine interest in high -quality sound.
If a good quadriphonic broadcasting
system was available, we'd listen to it:
if good
quad records were easy to find.
we'd buy them. And, if quad recording techniques became widespread.
we'd begin doing our own quad
sessions.
1f you go along with this, it's time
to get out a piece of paper and let the
FCC know of your interest. If you
(the listening public) can convince
them (the Commission) that quad
sound deserves to he heard, we may
live to see the end of this period of
quadriphonic confusion, and the heginning of a healthy market for four
channel hardware and software.
The inquiry before the FCC is
known as Docket 21310, and your
comments should he addressed to:
4i
Tr
(
/`
T(fVycyv
I rc^áJ0
qe,;,1_,,,.
BTX new
chronizer
vi
sync, any two
r)
IJ
.1;'
s
,-
,/-
4500 SMPTE edit code syn-
SMPTE time code.
completely self -contained system to sync your VTR
to your audio recorder, or to expand the number of audio tracks with two
multi -track recorders in tandem.
For complete information call The BTX Corporation, 438 Boston
Post Road, Weston, Massachusetts 02193 (617) 891 -1239.
c
sensible
ing
Use this
IC Op -Amp Cookbook by
Walter G. Jung. Explains
basic theory of the IC op
amp in a down -to -earth
manner. Includes over 250
practical circuit applica-
comments would he most welcome.
o
will bring into sync, and hold in
video or multi-track audio recorders us-
By the way, if you're already hooked
on quad, and are having trouble locating records, there's a mail -order house
that specializes in quadriphonic records and tapes. Write to Sound Concepts, P.O. Box 654, Peoria. Illinois
61652 and ask for Catalog 771.
And for more information on specific quad systems. the following addresses may come in handy:
CD -4 Discrete System
CD-4 Forum
45 Lakeside Drive
Rockville Centre, NY
Rockville Centre, NY 11570
And while you've got your pen out,
don't overlook db Magazine. We're
planning a quad update issue, and your
,1
`" - nJ
recorders for $3,850°
notice.
Stamford, CT 06905
Tc6r
Archróñizes
What's
cooking?
QS Matrix System
201 Communications. Inc.
201 East 42nd Street
New York, NY 10017
ovN
(.-,,
--tit
I
`"
o.,e,:
call.)
You have a chance to influence
the future of f.m. broadcasting, and
of the entire quad recording industry.. And your letter will he effective. The FCC wants to know how
you feel, so don't waste the opportunity. After all, when was the last time
the feds asked you for advice? Of
course, if you still feel that mono is
all we really need, please disregard this
CBS Technology Center
227 High Ridge Road
,,,,t"
wo
M,ÓOfTVA
.n1jVQ'7!+
Let the FCC know that you are interested in f.m. quadriphonic broadcasting, and that you will do what you
can to support it. once a standard has
been published. If you are ready to
buy quad hardware. by all means let
them know. (Relax, no salesman will
Matrix System
6r
6
Docket 21310
Federal Communications
Commission
1919 M Street, N.W.
Washington, D.C. 20554
SQ
C3_
My/
Circle 21 on Reader Service Card
tions. Fully illustrated and designed
for all interested in modern linear IC
design techniques. Covers general operating
procedures, such as offset nulling, frequency
compensation, and protection against abuses
and failures; signal -processing circuits; audio
circuits including low -level preamps, active filters and equalization circuits, power- booster
stages up to 100 watts, and a variety of other
specialized circuits. Includes unique devices
that cannot be categorized with standard types
programmable op amps, operational trans ductance amplifiers, quad current- differencinn
amplifiers, etc.
S12.95
-
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616 - 452 - 1596
Your Direct Line To
PROFESSIONAL
AUDIO
EQUIPMENT
We represent, stock, sell,
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such names as
Auditronics
Ampex
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SAGAMORE PUBLISHING CO, INC.
1120 Old Country Road.
Plainview, N.Y. 11803
Please send
copies of IC Op -Amp Cookbook
at $12.95. N.Y.S. residents add 8% sales tax.
..
Nortronics
Pulse Dymanics
Ramko
Revox
Distributors, Inc.
:'342 S. Division Avenue
Grand Rapids, Mich. 49507
CIAudio
Trades Welcome
Address
Anything That Doesn't Eat
Lease Plans Available
City
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State /Zip
www.americanradiohistory.com
Circle 34 on Reader Service Card
MARTIN DICKSTEIN
í Spund With Images
A Look At Some New A/V Devices
It happens often that people start
doing something, then are side- tracked
in the middle to something else, and
possibly move to still a third direction.
This occurred recently during a project
with which 1 was involved and resulted
in this view of a couple of audio /visual
maxell
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devices with which you may not be
familiar.
A synchronized slide program was
prepared in New York and sent to
another city where the cassette would
play the audio track as well as the
cues to trigger the slide advance action on a Kodak carousel projector.
The original programming was done
on a Model 2550 Wollensak cassette
recorder. The total system and program were the simplest arrangement
possible for a single- screen automatic
show.
In the out-of -town location, the person who would set up the show was
told to rent a Model 2550 unit, or a
2551, which is the later version of the
machine. For those unfamiliar with
these particular recorders, the 2550
has one track for the audio and a second track for the "beeps" which activate the forward motion of the projector. The tones are put on the tape
by a button on the recorder: at each
point in the program where a slide
movement is to take place. the button
is pressed and the cue is put on the
tape. The signals can be erased, rerecorded, and changed during the show
without necessarily having to do the
entire program's synchronization over.
although this can certainly he done if
desired.
The 2551 was made to operate with
the cues put on tape by the 2550, but
also had a button on it to put its own
tones on a tape. The signals put on by
the 2551 were I kHz, while the ones
from the 2550 were of a lower frequency. Therefore, the newer machine
was made with a switch on the side to
permit the user to go from the narrow
frequency position to "broadband."
Circle 23 on Reader Service Card
www.americanradiohistory.com
which would allow the 2550 signals to
operate satisfactorily. However, tapes
cued on a 2551 could not he used on
a 2550. The audio portion was fine.
of course, but the automatic signals
would not operate the cue electronics
in the older unit.
THE MISSING SWITCH
When the client in the other city set
up the equipment to play the tape, the
sound was okay, but the slides would
not move. In checking with New York,
it was found that the cable hookup
was right, the projector worked fine
by itself, and the "beep" switch on the
top of the machine was in the play
position. (This switch has three positions-off, to prevent cues on the tape
from activating the slides whenever a
pause is desired: play. the normal position for proper operation: and record, which puts the original cues on
the tape.) It was thei suggested that
the switch on the side of the 2551 was
in the wrong position. and should be
moved to "broadband:" otherwise the
cues from the 2550 would not work.
It was then learned that this particular
unit did not have the switch mentioned
although it was most definitely the
Model 2551. A second 2551 was
brought in. Same results. No 2550
was available. so a production person
from N.Y. was sent to the city with
the original 2550. Success! Everything
went well.
This incident led to a bit of an investigation on why the 2551 did not
have the broadband switch, and the
answer was rather simple. When the
2551 was first made. it did have a
switch on the side. It turned out that
there was a second model made after
the first one. and the original was not
being made anymore. The newer
Model 2551 would not work with the
cues from the 2550, but did operate
wth the signals from the original 2551.
This now meant that people with the
2550 tape had to carry their own 2550
unit with them, or he sure they could
get a model exactly like it wherever
they were going in order to he able to
use the tape. They could use the 2551.
if they were sure it was the old 2551
(with the broadband switch) not the
new. Most equipment rental firms like
to get the newest units available for
stock whenever they can, and rightly
so, but here is a situation about which
the user must be aware. It seems, therefore, essential that the companies which
rent these units should inform clients
who request one of these machines just
what the situation is regarding the
overlap of models. It can only create
good will when one is helpful.
NEW PROGRAMMING DEVICES
This experience led to an interest in
other models made by Wollensak. some
of which arc new and others that
might be unfamiliar to you. At a demonstration by Reliance Audio Visual
Corp. of some new Wollensak programming devices, Charles Spataro.
vice president for sales and rentals,
led the Reliance team at the presentation. Representatives of the 3M Company Mincom Division were also present. The showing introduced a cued cassette which triggered a new programmer, through dissolvers. to twelve slide
projectors on six screens -actually a
single screen with six images, three
wide horizontally and two high. Each
screen had two projectors in dissolve
to change the images.
Many of the units made by Wollensak in the slide synchronization field
were on display, and literature was
available for some not being shown.
For example. 3M makes Models 2548
and 2558. Both consist of a unit like
the 2551, mounted in an attache-like
suitcase with space for a slide projector.
and with a speaker in the cover. The
2548 is a recorder, while the 2558 is
a player only. Both have the same specs
as the 2551 (without the recording
capability in the 2558) and both operate on the 1.000 Hz. signal. The
2548 (like the 2551) has both separate output and input for audio and
the cue tones which allows for complete duplication of programmed cassettes.
Then there are Models 2556 and
the 2561. (Incidentally. all these model
numbers are followed by the letters
AV to indicate the visual applications
for synchronization with slides or film-
strip projectors.) These two models
are players only. The 2561 is portable
(like the 2551). Both 2556 and 2561
come with separate outputs for sync
and external speakers. Both are listed
as heavy duty. Another difference between the 2556 and the 2561 is that
the latter has inputs for hi -level or
mic audio. Thus, the unit can he used
for public address in either the stop
or playback mode: the mic is live in
both positions. This allows for separate commentary even while the program tape is going.
Then there are the 2570 and 2575.
The former is portable, and is also a
recorder. The latter is a deck only for
playback. Both units respond to the
1.000 Hz signal for slide advance. hut
also have an additional signal feature
150 Hz cue will stop the machines
automatically. This tone can he put on
by pressing a slop-restart button on
the 2570 during cue recording. In
order to restart the machines, there is
a provision for a remote program restart hand or foot control. These controls can also stop the machine and
then restart them remotely. Separate
sync and audio outputs permit complete cassette duplication of audio and
cue simultaneously. (The 2568 has a
257( version in a luggage -style suitcase with a speaker in the lid and space
for a slide projector.)
-a
MODELS 2573 AND 2590
Models 2573 and 2591) incorporate
more sophisticated features than any
of the others. The former called S_vne
//) includes the standard 1000 Hz
tone for slide advance and the 150 Hz
for automatic stop, but has the added
feature of also being able to control a
second slide projector or dissolve unit
with the lower frequency tone.
This is accomplished by a button
1000 Hz)
located between the Sync
and Sync H (150). When this button
is left in the normal up position. the
150 Hz signal will act as a stop. When
the mode selector is depressed. the 150
Hz signal acts a second cue for pro(
1
(
jector activation. Another capability of
the machine with its two sync pulses
is possible with the use of a special
cable and the Wollensak AV -33 dissolver. Using Sync I alone will cause
a single speed of dissolve. A second
speed is possible with Sync I1 alone.
When Sync 1 and Sync II are used together, a third speed becomes availThus, dissolve action can he
either slow, medium, or fast, and can
be programmed on the tape that way.
There is also a vu meter for audio
level control.
The 2590 also has three buttons for
sync operation, but they operate difable.
www.americanradiohistory.com
ferently. A 150 Hz signal will stop the
machine and a 1000 Hz tone will advance the slides. but a review button
permits checking preceding visuals as
far back as desired, in complete sync
with the tape. Thus, depressing the
review button momentarily brings hack
the previous slide and also the proper
audio. Keeping the button down returns the slides shown previously as
far hack as desired. When the button
is released, whether held momentarily
or kept down, the tape will automatically start again in sync with the slide
being shown at the point the button
was released. Both the 2573 and the
2590 have separate sync and audio
outputs and inputs. and both are recorders. There is also
which is a player only.
a
2595 model
MICRO -PRO 40
The newest item in the line is the
Micro-Pro 40 Multi -Image Memory
Programmer, the star of the presentation. Many people may he familiar
with previous programmers in the line.
the Digi -Cue Pro -6Q and the Pro -9Q.
in which the digits indicate the number
of available channels of the units. The
latest model has 40 -32 momentary
and 8 latching. The memory system provides for 1929 steps. all of which can
he transferred to tape in seconds and
verified for accuracy before putting on
the master with the audio. Programming is not required to he done in
real time (as it is done on the audio
cassette recorders discussed) and all
changes can he made easily at any
time. A numeric and l.e.d. display
hoard shows the operating mode.lthe
cue and frame being looked at. the
selected time intervals chosen for action (from 0.025 to 5 seconds in 8
steps or any combination of them).
and the entry /output display as well
as latching channel status.
Please he aware that this review of
the items does in no way indicate prefence over any other unit or any other
manufacturer. It is strictly intended as
an indication of the equipment available, and is meant to illustrate how
easy it is to he led from investigation
of one point into a variety of other
paths -and the interesting things that
can he learned. In subsequent discussions on this type of equipment. other
manufacturers will he examined thoroughly. The equipment described will
include dissolvers. power control units.
etc. This will all lead to a column on
-
multi -images and their applications
good and bad. If there are any special
subjects you wish to see discussed here.
just write. I promise to reach each and
every suggestion, and follow through.
if possible.
N
COMPACT LOUDSPEAKERS
New Products
& Servkes
REINFORCEMENT /RECORDING CONSOLE
Incorporating features applicable to
both sound reinforcement and recording. stereo mixing console Model 1202
has balanced Lo -Z and unbalanced HiZ mic connections on each input channel, in addition to line level signals for
multi -track recording. Three-band eq.
(bass, mid, and treble) with ±15 dB
range is included on each channel.
Pre /post capability is included for the
effects, reverb, and monitor send controls. Stereo pan and channel volume
controls are also included, as well as
variable gain control on the mic pre amp used in conjunction with the I.e.d.
peak indicator. Equalization provision
includes five -band eq. on the monitor
output and bass and treble controls giving reverb return eq. on the mains.
There is headphone volume and source
select monitoring, an auxiliary input
on each main, balanced outputs on
mains and monitor, and I.e.d. metering arrays.
Mfr: Tangent Systems. Inc.
Circle 51 on Reader Service Card
Twin
:4:
:
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14:
A COMPLETE CONSULTATION
DIRECT INPUT PREAMPLIFIER
OSCILLATOR /FREQUENCY
COUNTER
WORAM AUDIO ASSOCIATES
Consultants in Studio Systems
Engineering. Design and Installation
-offeringSERVICE FOR STUDIO
PLANNING AND
CONSTRUCTION
FREE -LANCE RECORDING
SERVICE IN THE
NEW YORK AREA
Direct input for low output moving
coil cartridges. with no transformer or
prepreamps required, is significant in
the design of RAM200 preamplifier.
All inputs look into f.e.t.s for low noise,
high impedance, non-reactive inputs.
All output circuits are class A complementary bipolar transistors. Range is
2 Hz to 80 kHz -!- 0.5 dB at any level
control setting. RIAA equalization is
30 Hz to 15 kHz ± 0.2 dB. Two
phono inputs with programmable resistive and capacitive loading allow
optimizing of the loading of phono
cartridges. HI and LO filters are 3pole active with 18 dB per octave
slopes. There is a built -in
watt -perchannel headphone amplifier, automatic or manual muting. a 36- position
attenuator switch, and a dual I.e.d. output level indicator, with 46 dB range.
I
516 764 -8900
45 Lakeside Dr.
Rockville Centre. N.Y. 11570
Mfr:
(D
N
loudspeakers. SRI12 and
identical characteristics
but differ in design for varied usage.
SR -112 is designed for permanent
installation indoors, with weather protection for limited outdoor use. SR116
is a portable unit with a carrying
handle. The speakers have the capacity to produce a sound pressure
level of 95.5 dB (at 4 ft.) with an
input power of one watt, providing a
full range frequency response over a
range of 45 Hz to 16,000 Hz without
frequency-correcting equalizers. They
are designed to operate with high
power amplifiers delivering up to 100
watts of continuous power to an 8ohm load. The units each use two
heavy -duty eight -inch bass speakers
and a high compression driver coupled
to a 120 degree radial horn. Low frequency performance comes through
the front -ported bass reflex design of
the enclosure.
Mfr: Shure Bros.
Price: SR 112: $340. SR l 16: $384.
Circle 52 on Reader Service Card
SR 116 have
Rant Audio Systems
Price: $1.000.00.
Circle 53 on Reader Service Card
Combined low distortion oscillator
and digital frequency counter Model
CB9109 handles IO Hz to 100 kHz in
four push button ranges, with eight
pre -set frequencies from 10 Hz to 20
kHz. A push button output attenuator
in 10 dB steps gives a 70 dB range.
plus fine control and mute button. The
frequency counter, which has a separate input accessible on the front
panel, gives continual display of oscillator output frequency in both sine
and square modes. The timing period
is selected by the frequency range push
buttons.
Mfr. Trident Artdio Developments Ltd.
Price: $507.00 (Approx)
Circle 54 on Reader Service Card
PROGRAMMABLE MIXER
Centralized control of the mixing
functions is possible with this computerized mixer. Designed to incorporate the techniques of numeric coding.
memorization, switching, and attenuation, the mixer memorizes pre -mixed
programs, assists manual mixing and
display, and complements existing installations. The mixer carries out the
first mixing level before proceeding to
a traditional console, centrally extending the number of input channels in
operation, actually controlled through
fewer channels by the operator. The
r"-^
mixer offers 12 inputs comprising pre amplification, overload indicator, and
attenuator; 4 groups of outputs; one
pre -listen. In programming, there are
15 different memorizations of all the
data for each of the 12 input channels, with the capacity of storing the
contents of these memories on a digital cassette, and permanent visual indication of its state on a display
terminal. The design includes a control panel enabling conversation with
the operator; a rack containing the
electronics; a digital Cassette for recording /reproducing: a crt display
terrminal.
Mfr: Conrpteurs Schlumherger
Circle 55 on Reader Service Card
DIRECT BOX
It is possible to record directly from
the amplifier or pickup of an elec-
®M 26999®t
i
tronic instrument with direct box DBP
1100. Input and instrument jacks are
multed to permit simultaneous recording and amplifier function. The box
can sit on rubber feet on any flat surface or snap onto a mie or music stand
with clamps. Input impedances are 20
Hz to 15 kHz, greater than 50k ohms:
I
kHz to 5 kHz greater than 100k
ohms. The ground on /ground lift
switch connects the chassis grounds of
the console to the guitar or guitar amp.
1
If
the signal source is an amp itself.
is provided. High frequency compensation to simulate the
response of a typical guitar or amplifier speaker is provided with a filter/
flat which goes into operation when
the pick up /amp switch is in the
"amp" position.
Mir: Westlake Audio
Circle 57 on Reader Service Card
a
pick up /amp
STEREO HEADPHONES
Wipe tapes clean
in record time.
r_Q
Garner Erasers
There are six passive radiators in
each earpiece of K -240 stereo headphones. The relationship between the
driver and the passive radiators is such
that the radiators are activated by
sound -pressure waves produced by the
active driver. At frequencies above
200 Hz the radiators are acoustically
transparent, eliminating mid- and high frequency cavity self- resonances. At
frequencies below 200 Hz the complying radiators provide bass response
without boominess.
Mir: AKG (Philips Audio
provide clean erasures in only four seconds -with
no noise residue. Tapes are wiped cleaner than
new. Our simple, safe, continuous belt operation
handles all sizes of reels, cartridges and cassettes
from 101/2" on down.
Garner Erasers
are
now fulfilling the exacting requirements of many
major organizations
around the world .. yet
.
are so low priced that the
smallest studio or station
can afford one.
User reports...
"lt is a big improvement over what we
used to use, or
anything else on the
market today."
-Ric Hammond
KNX Radio (CBS)
Hollywood, Calif.
a
Call today. Or write for
brochure and names of users
GARNER INDUSTRIES
Video
4200 N. 48th St.. Lincoln, NE 68504
Phone: 402- 464 -5911
Systems Corp.)
Circle 56 on Reader Service Card
Circle 24 on Reader Service Card
www.americanradiohistory.com
products & services (cont.)
MODULAR MIXER
Solid state audio mixer Model 100
fits into a standard electronic equipment rack. The line /mic mixer will
accept six line or six microphone inputs and has a monaural output. The
unit has a monitor capability, high and
low frequency equalization, and a vu
meter. The inputs and the program output are transformer isolated. Claimed
s/n ratios arc: mircrophone input. 78
dB ± dB and line input. 80 dB minimum. Maximum continuous sine wave
power is + 24 dBM ± 0.5 dB. Equalization is ± 20 dB at 20 Hz and 20
kHz and ± 14 dB at 100 Hz and 10
kHz.
MIXER EXPANDER
1
1
Mir:
Spectra Sonies
Price: $800.00.
Circle 58 on Reader Service Card
SPEAKER /PAGER
Portable KB-111P has all electronics mounted within a handled steel enclosure. including a 4 in. all- weather
speaker and 2 watt amplifier module.
The unit contains a combination call/
speaker mute switch. Both the portable
and the standard wall- mounted (KBI111 speakers have XLR -type connectors. front panel mounted, which fit
the manufacturer's handsets and headsets. KB-11 P also includes XLR -type
connectors side -mounted for input/
output looping. Two -conductor shielded
cable wires the speakers to remote or
main stations. Signal -to -noise ratio of
better than 55 dB is claimed.
1
Mir: Clear
Designed to complement Series
Model 5 mixer. 5EX expander can increase the inputs from eight to as
many as twenty. The extension unit is
equipped with eight 201 input modules. An additional four inputs are
optionally available. The expander retains all the functions of the Model 5
mixer, such as four line output busses.
a cue output bus, echo output bus. and
a solo output.
Mir: TEAC Corporation
Price: Under $1.300.
Circle 61 on Reader Service Card
MUSIC -RECORDING CONSOLE
Corn
Circle 59 on Reader Service Card
MINIATURE THREE -WAY SPEAKER
Uniform musical dispersion at all
frequencies, with in -depth reproduction
of instrumental individuality is claimed
for miniature L 300 stereo three -way
speaker. The driver complement consists of a 51/8 in. long excursion woofer.
a special dome mid -range and a linear
tweeter that extends the high frequency
response to 25.000 Hz. A computer
designed crossover network minimizes
phase anomalies and assures equal energy output over the entire musical
spectrum. Economy of space is achieved
by mounting the tweeter coaxially with
the woofer, but physical isolation of
the individual drivers is maintained.
The little unit weighs only 131/4 lbs.
and slips inconspicuously into cramped
areas.
Mir: Braun A. G.
CO
N
Price: $398 pair
Circle 60 on Reader Service Card
Expandable Types A and B Eclipse
studio consoles are designed specifically
for multi -channel music recording. The
units are available as 4 -. R -. 16-. 24and 32 -track systems with up to 40
input. Custom choice of equalizers offers a wide assortment, all of which
are interchangeable. including two
styles of graphic. Features include solo
in stereo position with echo; monitor
echo; two pannable effects returns:
two programmable mutes on each input; patching using professional size U4
in. jacks; illuminated color -coded channel selectors; stereo cue system; light
beam level displays available optionally.
Mir: Sphere Electronics
Circle 62 on Reader Service Card
John Woram's
The Recording
Studio Handbook
FOR RECORDING E\GNEERS,
TECHNCA\S AND ADOPHLES
The technique of creative sound recording has never been
more complex than it is today. The proliferation of new
devices and techniques require the recording engineer to
operate on a level of creativity somewhere between a
technical superman and a virtuoso knob -twirler. This is a
difficult and challenging road. But John Woram's new book
will chart the way.
The Recording Studio Handbook is an indispensable guide.
It is the audio industry's first complete handbook that deals
with every important aspect of recording technology.
Here are the eighteen chapters:
The Decibel
Sound
Microphone Design
Microphone Technique
Loudspeakers
Echo and Reverberation
Equalizers
Compressors, Limiters
and Expanders
Flanging and Phasing
Tape and Tape Recorder
Fundamentals
Magnetic Recording Tape
The Tape Recorder
Tape Recorder
Alignment
Noise and Noise
Reduction Principles
Studio Noise Reduction
Systems
The Modern Recording
Studio Console
The Recording Session
The Mixdown Session
In addition, there is a 36 -page glossary,
five other valuable appendices.
a
bibliography and
SAGAMORE PUBLISHING COMPANY, INC.
1120 Old Country Road, Plainview, N.Y. 11803
_
John Woram is the former Eastern vice president of the
Audio Engineering Society, and was a recording engineer at
RCA and Chief Engineer at Vanguard Recording Society. He
is now president of Woram Audio Associates.
Yes! Please sund
copies of The Recording Studio Handbook
at $35.00 each. On 15-day approval.
Name
This hard cover text has been selected by several universities
for their audio training programs. With 496 pages and
hundreds of illustrations, photographs and drawings, it is an
absolutely indispensable tool for anyone interested in the
current state of the recording art.
Address
City /State /Zip
Total Amount
N.Y.S. Residents add appropriate sales tax
coupon at the right to order your copy of The
Recording Studio Handbook. The price is only $35.00, sent
to you with a 15 -day money -back guarantee.
Use the
Enclosed in payment for $
Outside U.S.A. add $2.00 for postage
L
J
Sometime before the
sun comes up, you'll learn
to love your MM-1200.
Ampex gives you a lot of reasons to buy
an MM -1200 multichannel audio recorder:
capacity, fidelity, flexibility and reliability.
The performance specifications alone have
made this the best seller among professional
multitrack recorders.
But you'll find your own reasons for
loving the MM -1200 you buy.
Some morning, after a night of sessions
that dragged through the wee hours, you're
going to realize just how many MM -1200
features you used to keep things moving.
How you used the electronic tape timer,
plus search -to -cue, to save precious minutes
of time. How you used the quick -change
head feature to switch back and forth
between 8,16 and 24 track work. The ease
with which you employed the optional
accessories such as the pure video layback
head, synchronizer and variable speed
oscillator to finish the audio portion of a
video production.
The same professional drive for perfection that kept you going, kept our engineers
working to refine an already-respected
design.
That's why you see so many MM -1200s
in professional recording studios. Sooner
or later, before the sun comes up, everybody learns to love an MM -1200.
AMPEX
Ampex Corporation. AudioVideo Systems Division. 401 Broadway. Redwood City, California 94063, 415/367 -2011.
Circle 33 on Reader Service Card
www.americanradiohistory.com
ALAN FIERSTEIN
The Equalization Myth
Balanced room ambience, a time decay situation, cannot
be achieved by patchwork equalization.
equalization is the most widely
method of compensating for control
room acoustical faults. With a real -time analyzer (rta). the equalization process is fast,
simple, and cheap. Unfortunately, it is also wrong, because it overlooks the basic physical factors through
which rooms affect the sound of a loudspeaker.
Imagine a room with smooth, hard, totally reflective
surfaces. A sound introduced into this room would never
die away; it would just keep bouncing around forever. In
an anechoic chamber, however, sound is absorbed almost
instantly (as soon as it hits the first highly absorptive surface). These two rooms represent acoustical extremes
real rooms sound absorption takes a finite time. This time
varies for different frequencies. A carpet -lined room absorbs high frequencies quickly but the low frequencies
are absorbed much more slowly. The way these reverberation times, or T s, change at different frequencies is what
distinguishes one room's sound from another's. (T,;,, is defined as the interval in which sound pressure decreases by
60 dB after a steady -state sound has been abruptly shut off.)
MONITOR SYSTEM
used
-in
FREQUENCY- DEPENDENT T60
How do these frequency- dependent T s affect the loudspeaker's sound? First the sound emerging from the loudspeaker reaches your cars directly. The sound then hits a
surface which absorbs part of its energy, in relation to the
absorption curve of the surface material. A plywood panel
will absorb more energy from the low frequencies than it
will from the high frequencies that impinge upon it. The
carpeted room mentioned before has just the opposite effect. absorbing high frequencies. A number of reflections
multiply this absorption characteristic many times and
after the direct sound has passed, our cars still hear the
frequency- modified reverberation.
In the carpeted room we are left with a muddy sound.
since the high- frequencies were absorbed quickly. FIGURE
shows the result in a heavily carpeted room. The initial
sound consisted of two tones of a low and a high frequency
of equal volume. In the balanced room this sound has
decayed to a faithful miniaturization of the original, but
the heavily carpeted room has eaten up the highs and
changed the spectrum from that of the original sound.
Note that the high frequency wiggles are gone. We are
left with a decayed low- frequency note only, hence the
term "muddy sound. If you don't want a muddy reverberation, you must treat the room with materials that
absorb low frequencies as quickly as high frequencies. If
we had been listening to music. our ears would have
heard the new notes, plus the muddy reverberation of past
notes. giving the impression of added bass in the room.
1
equalize down the bass in the monitor system? No. Equalization only affects the initial amplitude of the sound; it
does not change the rate at which it decays. FIGURE 2
shows what happens when an attempt is made to equalize
problems like this. Please note that numbers and pictures
are exaggerated here for clarity.
In FIGURE 2 we see that the initial amplitude of the low
and high frequencies are both 100 dB. The T,;,, of the
balanced room is one second at all frequencies, so after
one second both tones have dropped to 40 dB, which is
essentially inaudible. Note that they both fell at the same
rate from the same level and crossed the inaudibility
threshold at the same time.
In the heavily-carpeted room with the muddy reverb,
FIGURE 3, we have attempted to compensate by equalizing
down the bass. The T of the bass is two seconds, and
the T,;,, of the treble is one second. If we equalized down
the bass 30 dB, it would start at an initial amplitude of
70 dB and fall 30 dB in the same time that the high frequencies would fall from 100 dB to 40 dB. Therefore both
tones would again become inaudible simultaneously. But
we have made the reverberation tonal balance correct at
one point only, at 40 dB, which is useless because since the
decay times are different at low and high frequencies. the
tonal balance is changing throughout the decay period.
Also, the direct sound is now totally non -flat.
By contrast, the balanced room of FIGURE 2 has a flat
direct sound, an unchanged tonal balance for the entire
decay period and both frequencies reach inaudibility together through the whole range. Clearly this is a much
more desirable situation than that created in the heavily
carpeted, heavily equalized room of FIGURE 3. The wonderful result of this balanced room is that a speaker that
is flat in an anechoic chamber will sound flat at the mixer's
ears, too, without equalization.
REAL -TIME ANALYZER
Contrary to popular opinion, a real -time analyzer does
not display in real time, for if it did our poor slow eyes
could not follow it. It integrates the input over a finite
time period with a slow decay that makes observing re-
Figure
1.
THIS. IN A HEAVILY
CARPETED ROOM
THIS SIGNAL DECAYS TO
EQUALIZATION FALLACY
Can we avoid treating the room acoustically and simply
rNi
Signal decay under differing conditions.
Alan Fierstein is president of Acoustilog. Inc. of
New York City.
www.americanradiohistory.com
OR
THIS, IN A BALANCED ROOM
INITIAL
INITIAL
I
70 eB
f\AAIINITIAL
100dB
100dB
SECOND
I
SECOND
INITIAL
70dß
I
40dB
40
VUV
Teo
125 Hz
I
SEC
T60 8 kHz
I
T60 125Hz
SEC
Figure 3. Decay in
equalized.
Figure 2. Ba lanced room decay.
verberation impossible. On the rta, the reverb of the
room adds to the display of the pink noise, and a non flat reverb characteristic will add more of some frequencies than others.
For example, on the rta, our carpeted room with the
muddy reverb will add low end to the display, giving the
impression that the initial sound is bass heavy and that
equalization is needed. The rta's blind addition of signal
and reverb is the root of the problem. Rtas are used with
pink noise, which is a static, continuous sound, as corn pared with music and speech which are impulsive in nature. Impulse sound is defined by its initial level and time
history,' and the rta simply adds level and time history
together in a way that our ears do not. Our cars hear the
effects of room reverb during the pauses of music and
speech. Pink noise has no such pauses.
How real is this effect in actual control rooms? Of
course, reverberation 20 dB or more below initial levels
will not add significantly to the curve height on a rta, but
the next 20 dB does. That the reverb is significant in affecting the rta's display is borne out by the fact that in a
room with a T,,,, of 0.2 second, significant reverberant
energy exists as close as three feet from the speaker. Obviously this depends upon other factors. most notably
speaker Q. But when a speaker whose one foot frequency
response of ±2 dB becomes i-12 dB at 8 feet (this actually occurred in a control room we measured) you can
see that the room reflections have a pretty heavy influence.
This wild response was not caused by standing waves.
This room was plagued by a non -uniform T,;,, vs. frequency curve. The ironic part of this story is that the
speaker itself is obviously quite flat ( ±2 dB) and yet the
room is giving this speaker a bad reputation ( ±12 dB). I
wonder how many engineers are condemning their innocent speakers!
In addition to all this, equalizing the monitor system
makes the important direct sound non -flat! Two rooms,
equalized flat, can (and often do) sound different for this
reason. Attempting to correct frequency- dependent time
decays with initial amplitude equalization is like adding
apples and oranges. This basic error occurs regardless of
whether you equalize to sine waves, pink noise, or "full spectrum" pulses.
ROOM TREATMENT
Properly treating a room is a complex job. What follows is merely a synopsis of common problems and solutions and is not meant to be a do -it- yourself guide to an
acoustics diploma. Employing an experienced consultant
is a wise decision if your room needs therapy.
Standing waves are a function of room dimensions and
shape. Flutter echo is caused by multiple reflections between parallel surfaces. Room modes are room resonances that occur closely spaced in frequency and tend to
reinforce their characteristic frequency when it is present
in the program material. These problems are minimized by
SECOND
I
SECOND
dB
a
2 SEC
T608kHz
I
SEC
room that is heavily carpeted and
designing a setting with few parallel surfaces, ensuring
adequate diffusion and by isolating room -resonant frequencies from each other by choosing optimum room
dimension ratios. These are mentioned in Reference 3.
Speaker placement can also affect standing waves.
A deep notch. characteristic of a high Q resonator, must
be searched out to find out what surface is vibrating. Then
stiffen it. These notches show up equally well with rtas
and with sine wave reverb measurements. The need for
symmetry and stereo separation must be also kept in mind.
These problems, although often severe, lay the groundwork
for the room T60 analysis.
With the gross problems out of the way, the absorption
is added, subtracted, or modified to provide the desired
T60 in each frequency band, usually octave bands. This can
be planned in advance to an extent by using tables of absorption coefficients that have been published for various
building materials. You multiply the square footage of
each material by its coefficient at each frequency, and then
you add up the total for each frequency and apply this
to a T,;,, equation such as the Norris-Eyring. But since no
one has published the absorption coefficient of your console, you'll need to take measurements of the Ta,, curve.
Some may want a control room with a reverb curve approaching that of a typical living room, or perhaps a
flat T60 vs. frequency curve is desired.
Finally, an equalizer can be used to fine tune the
speaker system if its anechoic chamber response needs
changing or if it was never tested in a chamber in the
first place due to its custom design (often the case in
studios). Usually the difference between one-foot and
eight -foot frequency response curves points out the degree to which room reverb is playing a part, and here a
rta is handy.
To sum up, control rooms are not equalizers or filters
(though they may appear to be on a rta screen). They are
time -decay absorbers. Do not correct rooms with amplitude changes (equalization); correct their T,;,, curves instead.
Equalizers are useful for fine tuning of speaker deficiencies that would show up in anechoic measurements.
or for electrical modification of a recorded track, etc.
When acoustical changes are not possible, as in many
sound -reinforcement applications. equalization has the additional use of allowing increases of acoustic gain if applied properly.4
REFERENCES
1. Beranek, L. L., Noise Reduction. McGraw -Hill, New
York. N.Y. 1960, pp. 145-151.
2. Rettinger,
M., Acoustic Design and Noise Control.
Chemical Publishing Co., New York, N.Y. 1973, pp. 27-28.
3. Everest, F. Alton, Acoustic Techniques for Home and
Studio. Tab Books, Summit, Pa., 1973, p. 68.
4. Davis, Don and Carolyn, Sound System Engineering.
Howard W. Sams & Co. Inc., Indianapolis, Ind., 1975, Chapter 8.
www.americanradiohistory.com
w
MARTIN DICKSTEIN
Music Alfresco in
Central Park
Reaching an audience of 100,000 while competing with big
city traffic and airplane drone is the Central Park assignment.
the N.Y. Philharmonic will be playing
its thirteenth season of free open air concerts at
Sheep Meadow in Central Park. This will also be
the second year for a newly designed sound rein-
THIS MONTH,
forcement system, and orchestra shell. The tremendous
improvement over the previous setup has been noticed and
voiced by both the public and music critics. To fully appreciate the achievement involved it's necessary to understand the obstacles that had to be overcome and the requirements set for the project.
The N.Y. Philharmonic usually plays in Avery Fisher
Hall at Lincoln Center. These indoor concerts have an
audience of about, 3,000 people with the most distant seat
about 130 feet away. In the open. the same orchestra can
play to about 100,000 people, with the outer fringe over
1,000 feet away. Since the area is not far from the busy
streets around the park, distractions such as sirens are not
uncommon. The Meadow also lies in one flight path of
planes going to and from N.Y.'s LaGuardia Airport.
In 1975. before the new system was put in, one newspaper critic. writing about a concert. said that the sound
was
pretty good. You have to acclimatize yourself
to its obviously tinny, amplified nature but that doesn't
take too long." Then, later, he continued with "Out on the
with even the closest speaker a long way
periphery
away, the sound is not very loud. It is thus easy to be
distracted by crying babies, noisy vendors and the occasional thoughtless talker or radio player."
To cover the area in question, the previous system utilized eight column speakers mounted over the stage roof,
similar units at about 50 feet forward of the stage, and
scaffold towers with multiple housings and low and high
frequency radial horns at the same distance in front of
the stage and about equidistant to either side. During the ten
years that the system and stage were in use, the sound
shell became less and less efficient, but the sound system
was kept working through continuous service.
In 1965, an item of over a half -million dollars was put
into the budget for a new shell and sound system. This
amount was covered by a grant from the Andrew Mellon
Foundation to the N.Y. Philharmonic and the Metropolitan Opera, which also uses the same facilities for its free
outdoor concerts in the same locations, and a grant from
the Booth Ferris Foundation.
system. The sound must be loud enough and must cover
the entire audience, it must be understandable, and must
be able to be used for all intended purposes. This new
system, however, had another critical requirement. Since
the performances of both the Philharmonic and the Met
also took place in four other locations in the city in addition to Manhattan, the entire shell, stage, and system had
to be made portable. The three -week performances of the
Met in June, and the three-week concerts of the orchestra
in August take place on consecutive nights (with one rain out night a week). This meant that the show had to be
designed for relative quick set up and tear down.
This speaker tower is 40 feet high and is rotated 180 degrees
circular ring directly under the mesh, which protects
the speakers from rain. Note the splay of the speakers for
total coverage.
on the
"...
...
OUTDOOR SOUND
c4)
There are several basic criteria for any outdoor sound
www.americanradiohistory.com
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View of the speaker tower at stage right with positioning for
full coverage of audience. The console position is at the
lower right.
The left of two racks mounted on the speaker tower truck bed
has an a.c. line meter. patch and connection panels, a mic
mixer, and 4 of the 8 amplifiers in the system.
Wenger Corporation of Owatonna, Minnesota, had previous experience with designing and building smaller orchestra enclosures incorporated into a truck trailer bed.
They were interested in expanding this concept to cover
the 40 x 70 ft. stage floor required for this new shell. The
acoustical consulting firm of Klepper Marshall King Associates of White Plains, N.Y. was selected to assist with the
design of the stage floor and the shell as well as the sound
system. To construct and install the new system. Rosner
Custom Sound of Long Island City, N.Y. was selected after
competitive bidding. Both the consulting and contracting
firms have long and impressive records of successful projects and were eminently qualified.
Since Sheep Meadow was the largest of the four areas
in which performances were given. this was used as the
guide for audience coverage. The live sound from the shell
would normally carry satisfactorily to a distance of about
fifty feet in front. so the system was designed to cover
from fifty feet out to at least 1.000 feet from the front
edge of the stage. At the front of the stage, the width of
the coverage would be 200 feet each side of the stage
center line, and out to 500 feet from the center line at a
distance of 1,000 feet from the stage. The frequency response was to he from 63 to 1,000 Hz within 3 dB and at
a slope off of 2 dB per octave from I kHz to 12.5 kHz.
again within 3 dB, and with no peaks outside of this range.
Noise and hum were to be inaudible at normal gain settings of the equipment.
The system was required to be able to reinforce live
music and speech from anywhere on the stage to a peak
level of 105 dB at 150 feet, and 99 dB at 300 feet. The
sound. within the area specified and with the levels mentioned. was to be "intelligible and natural sounding." One
further requirement of the system was that it was to incorporate existing equipment. This turned out to be no problem because Rosner Custom Sound had kept the units in
satisfactory condition for several years.
Set -up stage, with operating console at lower center of the
picture at stage right (where the group is standing). Note one
speaker unit in upright position.
ACOUSTIC ATMOSPHERE
The new shell was designed not only for sound distribution to the front audience but to reproduce, with improvements where possible, the previous acoustic atmosphere for
the musicians. The honeycomb panels which made up the
shell were
in. thick around the top and sides, and 2 in.
1
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The two sound racks are located on the speaker tower trailer
at truck bed level, with a matching pair on the other truck,
each speaker unit operating independently. On the left is a
mic mixer, patch and connection panels, a line level a.c.
meter, the master switch panel, and 4 amplifiers. The right
rack holds 4 amps, the corplimiter, the crossover network,
equalizer, and notch filter.
»
'
,
41.1
.,/
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16 -in /4 -our console with each input switchable to any of
lour line, two echo, and four monitor outputs. Each input
also has equalization controls.
tion. The speakers have also been sprayed with a special
protective coating for further defense against the elements.
EQUIPMENT RACKS
To help support the weight of the orchestra
piano, 1/4 in. thick composition board was
the floor panels. The walls and ceiling were
a simulated wood grain veneer.
The entire structure was carefully designed for its proper
acoustical function and aesthetics. The walls even included port openings which provided both acoustic treatment and ventilation. The unique shell was constructed in
three sections mounted on 40 -foot truck trailers. With the
truck beds carefully positioned adjacent to each other, the
entire shell could be raised hydraulically in place and lowered similarly for moving or storage.
The speaker system was designed as two towers. one on
each side of the stage. (Although a single cluster about 40
feet above the stage at the center might have been the
ideal solution, the weight could not be supported by the
shell ceiling. the proximity to the stage microphones could
prove to he an acoustic feedback problem, and the portability requirement added to the need for a different approach.) The towers each contain 28 speakers.
For low frequency (below 500 Hz), eight JBL 2220A
15 in. woofers are housed in four JBL bass horn cabinets.
From 500 Hz to 9500 Hz, four long -throw JBL 2356
horns and two short-throw JBL 2350 units are used with
2440 drivers. Above 9.5 kHz. twelve JBL 2405 tweeters
are used. For correct phase linearity, all drivers are aligned
on the same vertical axis. The speakers are stacked and
splayed at specific angles precisely defined for the desired
vertical and horizontal coverage. These towers, which rise
to a height of forty feet. have the speakers located in the
upper twenty feet.
Units in the tower are protected from weather on the
sides and back by panels. The front is covered with a
fiberglass mesh to prevent direct rain from getting to the
speakers. The towers are also designed for mounting on
a 28 ft. truck bed. The entire enclosure lies on the bed
with the speakers facing down, and thus is completely
protected from weather on top and sides. A covering is
also used for overall protection during storage periods.
When the two towers are raised hydraulically, they come
up facing away from the audience. They are rotated electrically 180 degrees and locked automatically in place for
proper orientation. The circular ring permits 360 degree
movement in either direction. The speakers are held in
place by 2 in. pipe, clamps, and guy wires of aircraft
cable. The guy wires are vinyl clad and the connections
are covered with caulking compound for weather protecon the floor.
and a grand
laminated to
covered with
The speaker tower truck beds also hold the equipment
racks, two for each tower. These are also protected from
the weather during storage and operation. Where the previous system was bi- amplified, the present one is tripowered. There are eight Bozak CMA2-80s per tower. The
15 in. woofers get 80 watts each, the mid -range horns get
40 each, and the tweeters get 20 each. Oil- filled, non electrolytic capacitors are used between the amplifiers and
the tweeter and mid -range drivers to protect them from
d.c. in the event of amplifier failure.
The right rack mounted on the truck bed at the foot of the
speaker tower contains 4 amps, a complimiter, an equalizer,
a notch filter, and a crossover for the speakers. A similar pair
of racks is located on the other speaker truck bed.
77i
IA'
Larry King adjusts a boom microphone, while Alex Rosner
(right) checks the positioning.
Still weather -protected, the left speaker tower is raised from
the truck bed into its upright position.
Alex Rosner at the portable console.
The audience can number up to 100,000, with some listeners
well over 1,000 feet from the stage.
Frequency separation at 500 Hz and 9.5 kHz is handled
a JBL 5234 2- channel electronic crossover network. A
UREI 560 tuneable notch filter feeds into the crossover
network and receives whatever minor adjustments might
be needed for maximum gain before feedback at each
performance. The notch filter is fed by an Altec 9860A
'/., octave equalizer. This unit is also adjusted as needed,
using pink noise.
Between the equalizer and the external mixing console
is a Spectrasonics 610 complimiter to control unusual peaks
of incoming sound. Also mounted in each rack is a Shure
M -67 mixer /preamplifier. An AKG BX -20 reverb generator and a Gotham Delta -T 101 digital time delay are also
available for connecting into the system. With the speaker
towers in the lowered position, the racks are completely
covered and protected against opening or removal. Access
for servicing is from the rear of the racks.
The control console is located at ground level at stage
right. It is a Yamaha PM 1000 with 16 channels in and
4 out. Two of the outputs are presently in use, one feeding
each amplifier /tower system. (The console can also be
used for stereo operation if ever desired.) Each of the
inputs is switchable to any of the outputs (four line, two
echo, four monitor). Every input has a straight line attenuator control, output assignment switches and variable
control equalizers. Each output line has an illuminated vu
meter with an overàll frequency response, within
dB.
from 50 to 15.000 Hz at a rated output of plus 18 dBm,
with 0.5 per cent or less harmonic distortion. The console
comes in a protective carrying case for portability.
When the system was fully installed and tested, it was
found, after adjustment of the L/.: octave equalizer to the
by
1
specified slope, that it was possible to achieve IOR dB at
I50 feet, 3 dB more than the specifications called for, with
some headroom still left. The gain was left at that point.
This setting gave a level of over 100 dB at 300 feet.
The noise was far below ambient sound and completely
inaudible.
The entire system, including the three trucks for the
shell and stage and the two for the towers, met the requirements for mobility and could be set up by a crew of
14 stagehands and 9 teamsters. The total system weighs in
at over 50 tons. In addition to these five, there are also
separate dressing room units, and a generator truck.
The new system has met with critical acclaim. Following
a performance by the Metropolitan Opera during the 1976
season, a music critic for the N.Y. Times wrote that "The
system... performed astonishingly well. A wanderer through
the Sheep Meadow found that the voices came through
clearly with recognizable color and individuality
Two months later, during the Philharmonic performances, the same critic wrote an article indicating his dislike for amplified systems outdoors and that the ideal
would be for the same 100,000 people not to listen to one
concert outdoors but for 1,000 to listen to 100 individual
indoor concerts. Following a Philharmonic concert in the
'76 season, another music critic for the same newspaper
wrote "Let others cavil at the misery of amplified music:
this night it gave pleasure to 100,000 New Yorkers, and
not many other things do nowadays." A tip of the hat
to David Klepper of Klepper Marshall King and Alex
Rosner of Rosner Custom Sound for a job well done and
also for their assistance in getting the material and pictures
for this article together.
www.americanradiohistory.com
..."
w
V
4,) Tust Report
BGW Model 100 -01
Power Amplifier
The BGW 100 -01 Power Amplifier.
m
co
Nor every need for a studio power amplifier demands super high power that also goes along
with a super high price. To meet this need,
several manufacturers have developed moderate
power units that meet both full professional standards of
performance, and yet still give high -fi standards of sound
quality. The latest of these is this new BGW Model 100 -01.
the 01 designation indicating a balanced line, transformer possible input. The amplifier is also available without this
option, whereby it is only unbalanced in.
The Model 100 is nominally rated by BGW as a 30 -watt
per channel stereo amplifier. This is probably a worst -case
designation since, as will be seen, our sample (at least)
performed rather better than that.
Physically, the unit takes up very little rack space -1.75
inches to be exact -and is but twelve inches deep. It weighs
a hefty eighteen pounds, testimony to its massive heat sinks
which contribute to the unit's conservative design.
The front panel is simple in layout with input gain pots
for the two channels and a pair of red light- emitting diodes
that are designed to ignite when the output is at clipping
level, or when it is shut down due to a short.
The rear panel has the input and output connections.
Input is via xlr -type connectors. An octal plug is next to
each input. An appropriate transformer or a (supplied)
jumper plug must be inserted here. Outputs are by paired
banana -plug lugs, so you can use single or double jacks.
wire wraps, lugs, just about anything that will make contact will do nicely.
The a.c. cord is heavy duty and is a three -wire type with
With the top cover removed, the clean construction becomes
obvious. Note the massive heat sinking.
The heavy heat sinks on the output devices, along with their
high power rating in excess of 120 watts, ensures
conservative operation at all times.
ground. While the standard amplifier is provided for 120V
operation, it can also he used on 220 volts by means of a
rear switch, and a recommended change of power -fuse
rating.
Once installed, the amplifier will properly feed any line
that is at least presenting a 4 ohm load to the outputs. The
front panel contains a stereo headphone jack. The internal
connections to this jack have a 270 -ohm resistor in series
with the hot sides so that gain to the headphones is under
control. Also, headphone insertion does not materially affect the load to the amplifier output.
One final physical fact about this amplifier is that it may
he internally bridged to become a more powerful mono
amplifier. This entails removing the top panel, flipping an
internal switch, and making speaker contact thereupon to
the two hot sides of the output. You will now have a mono
power output of RO watts.
LAB TESTS
Nu tests %%ere made of the mono ability of the amplifier.
Its stereo performance. however is exemplary in that it
not only met all its published specs. but was often orders
of magnitude better.
The full rated advertised power at 8 ohms is 30 watts
minimum sine wave continuous average power output per
channel, with both channels driving 8 -ohm loads over a
power band of 20 Hz to 20 kHz. The maximum total harmonic distortion at any power level from 250 milliwatts to
30 watts shall he no more than 0.1 per cent.
Here's what was found in the lab: Power at clipping
level with both channels driven into 8-ohm loads was
measured at 34 watts per channel midband, and 32 watts
per channel at the power extremes. Harmonic distortion
measured at both 20 Hz and 20 kHz 30 watts out resulted
in t.h.d. numbers of 0.0028 per cent at the bass end, and
0.062 per cent at 20 kHz.
There are no published specs on intermodulation dis-
tortion, but I measured it using the standard SMPTE 4:I
ratio (60 -6,000 Hz). At full power of 30 watts, the Model
100's i.m. distortion is 0.0037 per cent. It is also the same
at small signal levels of -3 watts.
Frequency bandwidth at these levels extends I Hz to 69
dB. Within
kHz. The envelope for that range is +0.
the 20- 20.000 Hz range, you can draw the frequency response with a ruler. As might he expected with this kind
of bandwidth, low frequency square waves revealed virtually no tilting, and higher frequencies showed no ringing
or rolloffs.
1
-3
Rear view of the amplifier showing connections.
And if you need a low noise amplifier, this unit's broadband noise measured -107 dB below 30 watts output.
Input sensitivity for full output is achieved with 0.78 volts.
Finally, a check was made to see what happens if the
load is 4 ohms rather than the stated and tested 8 ohms.
Power is greater. of course: now you can have 48 watts
per channel under the same driven conditions as before.
And distortion did not materially change. When a deliberate short was introduced in the output, the amplifier quickly
shut down, and the front panel I.e.d. ignited. Removing
the short restored power quickly.
The BGW Model 100 -01 is rugged and will surely give
long professional service. L.Z.
co
co
NOW
available
in
paperback
too!
44411
,;.
"Unequivocally, this is by
far the best text on microphones we've ever seen. "- Stereo
1
"So well written that it can be
clearly understood by a non -technical
person; for the professional it will probably be one of the most -used books in his
reference library. "- Journal of the SMPTE
And the rave reviews go on and
on. "At last...a decent book on
microphones," said David Lane
Josephson in Audio. "Excellent
chapters on various aspects of
microphones, which are discussed
in great detail," said Werner Freitag
in The Journal of the AES.
They're applauding Microphones:
Design and Application, by Lou
Burroughs, who has written this
practical, non -theoretical reference
manual for everyone involved in
the application of microphones
for tv, motion pictures, recording
and sound reinforcement.
Twenty -six fact -packed chapters
cover the field of microphones
from physical limitations, electroacoustic limitations, maintenance
and evaluation to applications,
accessories and associated
equipment. Each chapter is
crammed with experience- tested,
detailed information, and clear,
precise diagrams and illustrations
that complement the text.
á
Along with down -to -earth advice
on trouble -free microphone
applications, Lou Burroughs
unfolds dozens of invaluable
secrets learned during his more
than three decades of achievement
in the field. He solves the practical
"The chapter headings give a clear
idea of the down-to -earth contents
of the book ...each chapter contains
advice, direction, suggestions and
warnings couched in the clearest
and most unambiguous language
possible." (Journal of the SMPTE.)
Here are all 26 chapters.
Microphone Techniques
The Polar Response of a Microphone
Microphone Types
Microphone Loading
Rating Microphone Sensitivity
Microphone Overload
Proximity Effect
Temperature and Humidity Extremes
Microphones Electrically Out of Phase
Microphone Interference
Acoustic Phase Cancellation and the
Single Microphone
Microphone Maintenance (this chapter
alone "is worth the price of the book"
said D.F. Mikes in Audiovisual
Instruction)
Comparing Microphones with Dissimilar
Polar Patterns
The Monitor Speaker
Wide -Range vs. Controlled -Range
Frequency Response
Choosing Between an Omni-Directional
and a Cardioid Microphone
The Omni-Directional Microphone for
Orchestral Pickups
Assembling a Superior Bi- Directional
Microphone
The Two-to-One Ratio
Mitring for the Drama
Miking the Theatre for Audience Reaction
Wind Screens
Microphones on Booms
Acoustic Separators and the
Omni- Directional Microphone
The Hand -Held Microphone
The Lavalier Microphone
www.americanradiohistory.com
LC 73 -87056
ISBN 0-914130 -00 -5
problems you meet in everyday
situations, such as:
When would you choose a
cardioid, omni -directional,
or bi- directional mic?
How are
omni-directional mics
used for orchestral pickup?
How does dirt in the microphone
rob you of response?
How do you
space your
microphones to bring out
the best in each performer?
Microphones: Design and
Application. As Stereo put it,
"It's a hard book NOT to learn
from." Order your copies today.
Sagamore Publishing Co., Inc.
1120 Old Country Road,
Plainview, N.Y. 11803
Yes! Send MICROPHONES: DESIGN
AND APPLICATION.
_hardcover edition(s) @ $20.00
-paperback edition(s) @ $12.95
Name
Address
City /State /Zip
Total Amount
$
N.Y.S. Residents add 7% sales tax
$
`Outside
Enclosed is check for S
for postage.
U.S. add $1.00
J
Classified
Closing date is the fifteenth of the second month preceding the date of issue.
Send copies to: Classified Ad Dept.
db THE SOUND ENGINEERING MAGAZINE
1120 Old Country Road, Plainview. New lurk 11803
Rates are 50e a word for commercial advertisements.
Employment offered or employ ment wanted ads are accepted ai 25c per word.
Frequency discounts: 3 times, 10':: 6 times, 20': ; 12 times. 33'..
db Box number: $1.00 per issue.
All classified
ads must he prepaid. Frequency discount
advertisements are to he prepaid in ad%ance.
926 -6100.
I
TWO EVENTIDE digital delay lines, like
new. $2,300.00 each. (212) 765 -7790.
Soundesigns, Inc.
MXR'S DIGITAL DELAY system. Maxell
tape. all widths. discounted. N.A.B.
Audio, Box 7B, Ottawa, III. 61350.
RAZOR BLADES. single edge: tape editing. RALTEC, 25884 Highland, Cleveland, Ohio 44143.
A FEW competitively priced used Revox
MEASURE ROOM ACOUSTICS professionally. Acoustilog's Model 232 Reverberation Timer incorporates the following
advantages: one -person operation, 3%
accuracy, internal pink noise generator.
3 -digit readout. Acoustilog, 19 Mercer
St., New York, N.Y. 10013. (212) 9251365.
rebuilt
AMPEX SPARE PARTS; technical support; updating kits. for discontinued professional audio models; available from
VIF International, Box 1555, Mountain
View, Ca. 94042. (408) 739 -9740.
MCI 24 -TRACK recording console with
producer's desk;
matching equipment
rack; plus extras. $19,500. (312) 2252110, Paul.
CROWN INTERNATIONAL. Complete repair; overhaul, and rebuilding service
for current and early model Crown tape
recorders and amplifiers. New and re-
conditioned recorders in stock for immediate delivery. Used Crown recorders
purchased and accepted for trade in.
TECHNIARTS, 8555 Fenton St., Silver
Spring, Md. 20910. (301) 585 -1118.
NAGY SHEAR -TYPE TAPE SPLICERS
FOR CASSETTE Vi
Sh
A77 and A700 decks available. Completely reconditioned by Revox, virtually
indistinguishable from new and have
the standard Revox 90 -day warranty for
machines. Satisfaction
2620.
STUDIO SOUND-Europe's leading professional magazine. Back issues available from January '74 through June '75.
$1 each postpaid. 3P Recording, P.O.
Box 99549, San Francisco, Ca. 94109.
TECHNIARTS, professional audio equipment: AKG. Ampex, Crown International,
dbx, Malatchi, Orban Parasound, Sescorn, in stock. Professional audio services: audio and acoustical analysis,
narrow band equalization, reverberation
time, frequency response, and noise level
measurements, broadcast and recording
systems design, fabrication, and installation. TECHNIARTS, 8555 Fenton St., Silver Spring, Md. 20910. (301) 585-1118.
TASCAM 80 -8's in stock; Loft Modular
recording consoles; AKG, Shure, E -V.
and Sennheiser microphones; AKG reverb; Eventide; Crown; Parasound; Sentry Ill's and IVB's. Call today. ask for
Ben at Rowton Professional Audio, Paducah, Ky (502) 898 -6203.
FREE
CATALOG a AUDIO
NRPD
f
IN. TAPES
POWER
FAST, ACCURATE
Box 289 McLean, Va. 22101
APPLICATIONS
CONSOLES
KITS
WIRED
AMPLIFIERS
MIC., EO ACN,
LINE, TAPE, DISC,
&
SELFSHARPENING
guaran-
teed. Write requirements to ESSI, Box
854, Hicksville, N.Y. 11802. (516) 921-
HANDCRAFTED
FIELD PROVEN
-.
®
COMPUMIX -i 24-channel mixing system,
self contained, perfect condition, interfaces to any board, $10,000. Ampex
MM -1100 16- track, $15,000. Both $23,000.
AG- 440 -4C plus 2 -track block, console
$4,600. TM -499 digital delay. $1,300. All
items 10 months old. (303) 499 -0545
evenings.
SOUNDESIGNS. authorized 3M dealership and repair service; carrying all
professional machines and parts: 24. 16,
8, 4, 2- track, Selectake
and II. Call
Soundesigns, Inc., Artie Johnson, at
(212) 765 -7790.
FOR SALE
SOUND SYSTEM design and installation, loudspeaker enclosures for professional
applications, custom passive
crosssover assemblies, room equalization, road equipment cases. touring
sound rental. Kill Pro Audio, 75 N.
Beacon St., Watertown, Mass. (617)
SOUNDCRAFT MIXING CONSOLES for
recording and sound reinforcement
available exclusively in New England at:
K&L Pro Audio, 75 N. Beacon St., Watertown, Mass. 02172. (617) 926 -6100.
OSCILLATORS
AUDIO
OPAMP LABSNC.
iiii
TAPE BIAS
POWER SUPPLIES
RACK LABS active fixed or variable frequency crossovers, disco mixers, and
ULF (subsonic) filters. Write' 136 Park
St. New Haven, Ct. 06511.
/v Neve
NEW AND USED
MIXING CONSOLES
SALES -RENTAL -LEASE:
NEW 24 TRACK CONSOLES, often
available from stock or on short
notice. Budgetary prices are:
Model 8058. 28-in, $66,900. Model
8068, 32 -in, $77.900. Model 8084
32
8 -in, $89.900. Get all the details on these and other price competitive consoles, built to the
highest standards. Leasing programs available, subject to terms.
TRADE-IN CONSOLES in excellent
condition may be available from
time to time, due to our many
satisfied customers wishing to upgrade to larger Neve consoles.
Typical prices are: Model 8314, 16in/8 track $20,000. Model 8036.
24 -in /16 track, $40,000. Model
8048, 32 -in /24 track, $70,000.
Leasing programs available, subject to terms.
RENTAL CONSOLES may be available for short use. Typical monthly
rates are: Model 8301, 10 -in /2out, $550. Model 5305, 20 -in /4out, $1,200. Model 8036, 24- in /16track. $2,200. Model 8053. 28 -in/
24- track, $2,800. Weekly rates
upon request. Subject :o terms
and availability. All prices are
subject to change without prior
notice. FOB points are Bethel.
Conn. or Toronto, Ontario. Sales
and use taxes not included.
Rupert Neve Incorporated
Berkshire Industrial Park
Bethel, Conn. 06801
(203) 744 -6230
In Canada (416) 677 -6611
:`
(continued)
TASCAM. TEAC. Sound Workshop. Nakamichi. Otani. dbx. MXR. Dynaco. ADS.
Eventide, E -V. Shure. Maxell. Ampex.
AKG Pro. Beyer, UREI. Stax. Sennheiser.
TAPCO. BGW. and more! Send for price
quotes. Zimet Pro Audio, Dept. DB,
1038 Northern Blvd., Roslyn, N.Y.
11576.
THE LIBRARY
Sound effects recorded in STEREO using Dolby throughout. Over 350 effects on ten discs.
$100.00. Write The Library, P.O. Box
18145, Denver, Colo. 80218.
.
.
.
TRACKS!! The complete semi -pro recording center. Check our low prices
on Tascam, TEAC. Neotek. Micmix.
dbx, Multi- Track. MXR, Sennheiser.
BGW. Shure, TAPCO. and many others.
Complete studio packages available.
TRACKS!! from DJ's Music, Ltd. 9520
47th St., Brookfield, III. 60513. (312)
485 -0020.
is more than a reverb. Designed for use with any console,
including Tascam. $359.00. Dyma, Box
1697, Taos, N.M. 87571.
THE RESONATOR
MODERN RECORDING TECHNIQUES by
Robert E. Runstein. The only book covering all aspects of multi -track pop
from
microphones
music recording
through disc cutting. For engineers, producers. and musicians. $9.95 prepaid.
Robert E. Runstein, 44 Dinsmore Ave.
Apt. 610, Framingham, Mass. 01701.
$2 MILLION USED RECORDING EQUIP-
MENT. Send $1.00 for list, refundable, to
The Equipment Locator, P.O. Box 99569,
San Francisco, Ca. 94109.
PRO AUDIO EQUIPMENT &
SERVICES
P.A. and custom touring sound systems, studio equipment, and turnkey installations, theatre and disco
sound. Representing over 100
N
V
lines, including: AKG, Allen &
Heath, Alembic. Community Light
& Sound, dbx. Denon, Dokorder,
Dynaco, Emilar, ESS -Pro, E -V. Forsythe Audio, Fons. Furman. Gallien- Kruger, Gale, Gauss, Goldring,
Grace, J&H Formula 4, Kelsey.
Koss, Lamb, Langevin, 3M. 3A.
Marantz, Meteor, Mitsubishi, Max ell. Malatchi, MXR -Pro. Otani. Rus sound. Revox. SAEC, Sennheiser.
Scotch. Shure, Sonab. Sound
Craftsman.
Soundcraft, Sound
Workshop, Sony, Switchcraft. Ses corn. Stax. Supex, TAPCO, TDX.
Tascam, Technics. TEAC, Thor ens. Uher. West Penn. All equipment on display in a working environment. Competitive pricing and
comprehensive service.
K &L Pro Audio, 75 N. Beacon St.,
Watertown, Mass. 02172
(617) 926 -6100 (Att. Ken Berger)
AUDIO and VIDEO
On a Professional Level
Lebow Labs specializes in equipment sales, systems engineering.
and installation -full service and
demonstration facilities in- house.
We represent over 200 manufacturers of professional and semiprofessional equipment for recording, broadcast, sound reinforcement, and for commercial sound.
Call or write for information and
pricing.
CUTTERHEAD REPAIR SERVICE for all
models Westrex, HAECO, Grampian.
Modifications dore on Westrex. Avoid
costly down time; 3 -day turnaround upon
receipt. Send for free brochure: International Cutterhead Repair, 194 Kings
Ct., Teaneck, N.J. 07666. (201) 8371289.
SPECTRA SONICS custom console 16 x
16, 32 pan pots. Currently in use; good
quiet board. $11,000 or best offer. Fifth
Floor Recording. (513) 651 -1871.
LEBOW LABS, INC.
424 Cambridge St.
Allston (Boston) Mass, 02134
(617) 782 -0600
AMPEX TAPE. Ampex Audio studio
mastering tapes; 631 -641, 406 -407, and
"Grand Master" in stock for immediate
shipment; I/4", 1" and 2 "; factory fresh.
Best prices. Techniarts, 8555 Fenton
St., Silver Spring, Md. 20910. (301)
585 -1118.
TEST RECORD for equalizing stereo
systems. Helps you sell equalizers and
installation services. Pink noise in 1h
octave bands, type QR- 2011 -1 @ $20.
Used with precision sound level meter
or B & K 2219S. B &K Instruments, Inc.,
5111 W. 164th St., Cleveland, Ohio
44142.
AMPEX, SCULLY, TASCAM, all major
professional audio lines. Top dollar
trade -ins, 15 minutes George Washington Bridge. Professional Audio Video
Corporation, 342 Main St., Paterson,
N.J. 07505. (201) 523 -3333.
-
LIGHTING DIMMER SYSTEM for sale.
32
3k dimmers, 32 faders with 16
preset memory console. Packed for
touring. Must sell! BC &G Enterprises,
P.O. Box 1036, Littleton, Colorad3
80160. (303) 751 -5991.
4560 KIT! Using new Community fiberglass flare and one sheet of plywood.
Use 15" speaker of your choice. Only
$115! Order now from Gary Gand
Music, 172 Skokie Valley Rd., Highland
Park, III. 60035. (312) 831 -3080.
24- CHANNEL Sound Reinforcement Mixer, 100 -ft. snake, balanced input. 3 -band
eq., 3 submixers, monitor. echo, solo.
Also UREI Model 527A Graphic Equalizer. Best offer! BC &G Enterprises, P.O.
Box 1036, Littleton, Colorado 80160.
(303) 751 -5991.
PIEZO SUPER TWEETERS. Good quantities in stock; specifications sent if requested. $4.62 -$9.50, depending on quantity. Musimatic, Inc., 4187 Glenwood
Rd., Decatur, Ga. 30032. (404) 289-
5159.
AMPEX SERVICE COMPANY: Complete
factory service for Ampex equipment;
professional audio; one -inch helical
scan video; video closed circuit cameras; video systems; instrumentation
and consumer audio. Service available at
2201 Lunt Avenue, Elk Grove Village,
IL 60007; 500 Rodier Drive, Glendale,
CA 91201; 75 Commerce Way, Hackensack, NJ 07601.
AUDIOARTS ENGINEERING parametric
equalizer, electronic crossover. disco
mixer, stage mixers. Audioarts Engineering, 286 Downs Rd., Bethany, Conn.
06525.
REELS AND BOXES 5" and 7" large
and small hubs; heavy duty white boxes.
W -M Sales, 111 B Dula Circle, Duncanville, Texas 75116. (214) 296 -2773.
MAXELL, AMPEX. Capitol and Columbia reel tape; bulk and custom loaded.
Custom length duplicator cassettes.
Reels, boxes, leader tape. splicers. For
complete catalog. write Omega Audio
Products, Box 39253, Redford, Michigan 48239.
SOUND WORKSHOP mixing consoles.
reverbs and support equipment setting
new standards in the semi -pro industry
available in New England at: K &L Pro
Audio, 75 N. Beacon St., Watertown,
Mass. 02172. (617) 926 -6100.
PROFESSIONAL SOUND COMPONENTS
from Crown, TAPCO, Soundcraft, Eventide, Community, Malatchi, Tascam, Biamp, dbx, Gauss. Spider /Peavey, Sound
Workshop, and many more. Hear it all at
Gary Gand Music, 172 Skokie Valley
Rd., Highland Park, III. 60035. (312)
831 -3080.
INCREASE YOUR USABLE P.A.
SYSTEM'S POWER WITH BODE
FEEDBACK SUPPRESSOR.
MODEL 741XR
Also featuring a complete line of
studio and performance frequency
shifters. For details contact:
Bode Sound Co.
1344 Abington PI.
N.
Tonawanda, N.Y. 14120
(716) 692 -1670
SPECTRA SONICS, 20 input, 16 bus; 16track monitor with 2 cue feeds, 2 -position eq., selectable frequency, cue and
echo send; stereo /mono busses. Currently installed; converting room to a
24 -track system. Highest bid. Contact
Larrabee Sound, (213) 657 -6750.
AST: THE PROFESSIONAL SOUND
STORE. Full line of ALTEC, CROWN,
CERWIN -VEGA, E -V, GAUSS, SHURE,
SUNNI, and ATLAS pro sound equipment; factory authorized service on most
speakers. Large stock of ALTEC, CERWIN -VEGA and E -V replacement diaphragm assemblies available. AST, 281
Church St., New York, N.Y. 10013.
(212) 226 -7781.
NEW CUSTOM CONSOLE, factory war rantied, original customer unable to take
delivery. Construction stopped at point
where expansion above original 10 -in /8out configuration is possible. 3- band /9
frequency equalizer on inputs and echo
return. Ultra -quiet electronics with 4-26
dBM output. Terms available. Call Gordon: Clark Research Co., 59 -101st St.,
Ft. Lee, N.J. 07024. (201) 947.4810.
4 -track 1/2 -in. deck, identical to
Ampex AG -440; new Electro -Sound pinch
roller; STL alignment tape; 5 reels unused tape. $2,500.00. Harry Minot, 81
Olcott Way, Ridgefield, Conn. 06877.
(212) 754 -1100.
SCULLY 100 16 -track recorder.
good condition. $10,500.00 (212) 7657790. Soundesigns, Inc.
ONE
STEINWAY GRAND PIANOS
sold, rebuilt. (212) 693 -1363.
bought,
TASCAM Model 5 console, $1,250. Also
Gallien Krueger 4002 series bass bottom.
$250. Both units new. (516) 751 -8389.
BUSINESS OPPORTUNITIES
RECORDING STUDIO. Professional 8track sound studio currently operating in
the Washington, D.C. area. Good location with room for expansion and good
potential. $30.000 takes all or will sell
equipment individually. For more information and equipment list write Dept.
71, db Magazine, 1120 Old Country
Rd., Plainview, N.Y. 11803.
WANTED
EQUIPMENT
WANTED:
NEUMANN;
AKG.Sennheiser microphones; miscellaneous outboard gear, etc. Call or write:
Dan Alexander, 1345 Grove St., Berkeley, Ca. 94709. (415) 232 -7933.
VEGA
STAGE / STUDIO / BROADCAST audio
systems: AKG, Allison Research, Amber.
Amco, Auditronics, Beyer, Cannon, dbx.
E -V, Eltech, Eventide Clockworks, [vie,
JBL, Lexicon, MicMix. MRL, Nagra, Neotek. Neumann, Nortronics, Orban /Parasound, Orange County, Otari, Pultec,
Robins, Russco, Scully, Sennheiser,
Sescom, Shure, Sony, Soundcraft, Speck,
Switchcraft, Spectra Sonics, 3 -M, Tascam, U.M.C., White, & UREI, plus many
more. For further information on these
and other specialty items from our factory operations contact: Midwest Sound
Co., 4346 W. 63rd St., Chicago, III.
60629. (312) 767 -7272.
TWO AMPEX MM -1000 16 -track recorders, excellent condition. Priced for quick
sale. (212) 765 -7790. Soundesigns, Inc.
PARTS IN STOCK for Ampex, Bose,
TEAC, Crown, SAE, Uher. Also fast professional service to your equipment.
Jones Electronics, 947 Old York Rd.,
Abington, Pa. 19001. (215) 885 -4190.
RECORDERS, excellent condition. Ampex MM -1000 and Scully 280,
$6,300 each, firm. Datacope. (501) 6668588.
8 -TRACK
REVOX A700 stereo 1/2-track recorder.
N.A.B. adaptors, excellent, $1,440. Stellavox SP7 stereo 1/z -track portable
plus accessories, excellent, $2,200. Gerald Whelan, 8747 Twin Creek Dr.,
Franklin, Ohio 45005.
WANTED: BULK CASSETTE duplication.
using mono heads only. VERY picky
about quality. 1/4" running master supplied. Send prices 100, 500, 1,000.
Sound By Blachly, Box 4328, Austin,
Texas 78765.
WANTED: TRANSCRIPTION discs. any
size. speed. Radio shows music. Box
724 -db, Redmond, Wa. 98052.
EMPLOYMENT
TM PRODUCTIONS,
largest radio commercial and ID firm, is now screening
applicants for top engineering /mixing
position. Must be a dedicated pro, and
one of the best. Exceptional sense of
organization and efficiency essential. Unlimited opportunities with the fastest
growing production house in the U.S.
Send resume, sample mixes, and salary
requirements to Ken Justïss, Operations
Mgr., TM Productions, 1349 Regal Row,
Dallas, Texas 75247. Absolutely no
phone calls accepted.
APPLIED AUDIO WRITER /CONSULTANT. National consumer audio -music
magazine based in New York seeks experienced journalist with solid back-
ground in professional recording techniques, electronics, and electronic musical instruments. Send resume and writing samples to Dept. 81, db Magazine,
1120 Old Country Rd., Plainview, N.Y.
11803.
EXPERIENCED MUSIC MIXER
Major N.Y.C. studio. New automated 24- track. Send resume to
Dept. 83, db Magazine, 1120 Old
Country Rd., Plainview, N.Y.
11803.
www.americanradiohistory.com
PROFESSIONAL AUDIO SERVICE technician, part time, with opportunity for
full -time if satisfactory. Metropolitan
Washington, D.C. area. Send background
and experience to db Magazine, Dept.
82, 1120 Old Country Rd., Plainview,
N.Y. 11803.
WANTED: Young, gifted sound engineer
for college studio. Thorough understanding of mechanics, multiple -track recording equipment and capacity to do "mixing." Ours is the most sophisticated production program in the Midwest and with
a sound facility that is first -rate but
eclectric-an improved collection of machinery that requires talented attention.
The right person for this job probably
functions comfortably as a film sound
man, has a mechanical aptitude, and
might want to be a mixer one day or run
his own sound studio. He should be
committed to film. Salary negotiable.
The right person might also teach on a
part -time basis. An added attraction is
the fact that we are central tc film action in Chicago and that means the possibility of free lance work, additional income. Send resume, stressing background, credits. capacity, etc., addressed
to: Anthony Loeb, Chairman, Film Department, Columbia College, 600 S.
Michigan Ave., Chicago, Ill. 60605. An
equal opportunity employer.
PROJECT MANAGER /ENGINEER to take
charge of design, fabrication, and installation of complex professional sound
systems for large auditoriums, arenas,
buildings, etc. You must have an EE degree or equivalent experience, and a
proven record of accomplishments. Position offers significant individual recognition. Age no hindrance. This is a new
position in our expanding engineering department and is an excellent opportunity
to join the national leader. Salary open.
Phone or write, Mr. David Butz in strict
confidence. New Jersey Communications
Corporation, Kenilworth, N.J. 07033.
(201) 245 -8000.
POSITIONS AVAILABLE. Concert sound/
lighting /scenic technicians and engineers needed. MUST have road experience and references. Full -time. salaried employment. Send resume or call
the Alpha Organization, 6910 Raleigh
La Grange Rd., Memphis, Tenn. (901)
388 -1032.
Audio Circuit
Design Engineer
Due to recent expansion and increased
business activities UREI has an opening
for a product designer. Applicant must
have substantial experience in all
phases of audio circuit design, B.S.
preferred.
UREI
offers competitive
salaries and excellent benefits.
8460 San Fernando Road
Sun Valley, Calif. 91352
Forward resumes to F..B.Combs
l5
A
41
People/Places/Happening
An American subsidiary, based in
Chicago. has been set up by British
Audio & Design Recording. The new
company, operating under the name of
Audio & Design Recording, Inc., is
located at 1019 N. Winchester, Chicago, II. 60622. Officers of the company include president Gregg Dixon;
chairman. Mike Beville; vice presidents. Ian Harley, Steve Miller. and
Len Lewis.
International shuffling has been taking place at Spectrol Electronics Corp..
of City of Industry. Ca. Roger Jones
is being transferred to Swindon. England as general manager of Spectrol
Reliance, Ltd. Martin Hankinson, formerly managing director of the Swindon
operation, is returning to California, to
become director of marketing. Lee
Chapman is returning from chores at
SP Elettronica spa in Milan. Italy to
California to become manager of Spectrol Electronic Controls. His place is
being taken by George Artiano.
A line of electronic musical instruments has been accumulating at fledgling Aries Music, Inc. of Salem. Mass.
founded last April. Principals in the
firm are Robert A. Snowdale, Jim Bastable, and June Richards. Production
centers around the Aries 300 series of
modules, first manufactured in 1974.
Referring of the school as "a well established San Francisco educational
institution which provides exceptional
training to its students," Mayor George
Moscone recently issued a special proclamation saluting the College for Recording Arts. Leo de Gar Kulka, dean
of the college. was also personally congratulated by Mayor Moscone for the
guidance he offers his students. The
college is located at 665 Harrison St..
San Francisco.
Daniel E. Denham, vice president of
the 3M Company Recording Materials
Group, was recently named the International Tape Association /Time, Inc:s
Man of the Year. The citation, presented by Fred Bronner of Time. Inc..
highlighted Mr. Denman's efforts in
establishing minimum world-wide standards for tape production.
Announcement has been made of
the appointment fo Leon Wortman to
the post of marketing manager at Otari
Corporation, of San Carlos, Ca. Mr.
Wortman had been active in sales in
the Ampex and Scully companies before coming to Otari.
Record- breaking demand for space
at the forthcoming (October 16 -21)
SMPTE Conference has led to the
establishment of 72 additional booths.
Site of the conference is the Century
Plaza Hotel in Los Angeles. For information, contact SMPTE, 862 Scarsdale
Ave.. Scarsdale, N.Y. 10583.
The Elrep Sales Company of Tucker
Ga. has been appointed to represent
AKG Acoustics of Mahwah. N.J. in
handling dealer relations. Ben Van de
Kreke, president of Elrep. is the contact person.
Representatives in 17 cities have
been chosen to handle the Syn -AudCon three -day sound engineering seminars conducted by Don and Carolyn
Davis of Synergetic Audio Concepts,
Tustin, Ca. The coordinators include
Forti-Austin Associates, Billingboro.
N.J.; Bidwell Sales Assoc., Carson, Ca.:
Moulthrop Sales, Inc., Oakland, Ca.:
Fleehart & Sullivan, Inc., Seattle. Wa.:
Dobbs- Stanford Corp., Irving, Tx.:
Forristal -Young Sales Co., Kansas
City. Mo.: Jamieson & Associates, Inc.,
Minneapolis. Mn.: Ray R. Hutmacher
Assoc., Chicago. II.; McFadden Sales,
Columbus. Oh.: Diversified Concepts.
Marcellus. N.Y.; Iry Bron Company.
Brooklyn. N.Y.: Ballon & Assoc.,
Southington. Ct.: Lineau Assoc., Inc..
Rockville, Md.
Two sophisticated tape -to -disc mastering facilities manufactured by Neumann of West Berlin and installed by
Gotham Audio Corporation of New
York and Hollywood have been placed
in San Juan, Puerto Rico at Ochoa Recording Studios and at Diskwerks, Inc.
of Schaumberg. Ill. The Ochoa system
has an A -80 preview tape machine.
SP-75 program console. Neumann
VMS -70 computer disc cutting lathe
and SX -74 stereo cutterhead. The Diskwerks system also includes the first
SP-77 transfer console ever installed.
Hungarian-produced Videoton stereo
speaker systems are now available to
Northwest users through newly appointed representative Spectrum Northwest Marketing, Inc. of Portland, Oregon. Spectrum will market the speakers
in Oregon, Washington. Montana,
Idaho, and Hawaii. The national outlet
for Videoton is Kelso Imports, of New
York City.
Charles Condike has been promoted
to the position of vice president of the
distributor division of Robins Industries Corporation, of Commack. N.Y.
Before joining Robins in 1976, Mr.
Condike was with British Industries
Company. Another promotion is the
appointment of Steven N. Friedman as
vice president of professional products.
Mr. Friedman had been serving as
senior engineer for the firm.
Returning to West L.A. Music in
Los Angeles after an interim with
Sunn Musical Equipment in Portland.
Gregg Hildebrandt has assumed the
post of vice president and general manager of the L.A. firm. West L.A. Music
is a retail outlet for musical instruments, sound systems. and recording
equipment.
Supplying the professional recording industry, as well as sound reinforcement and semi -pro audio needs.
Audio Marketing, Ltd., has been
formed as a wholly owned subsidiary
of Audiotechniques, of Stamford.
Conn. Richard Anderson, former product manager at Audiotechniques, will
serve as the general manager of the
new company.
The need for a ten -second delay device for television electronic news gathering equipment was stressed recently
by Robert Flanders, vice president of
engineering at McGraw -Hill Broadcasting Company and chairman of the
NAB Engineering Advisory Committee.
With the proliferation of live iv. news
broadcasts. the danger exists of exposing the public to an uncontrolled situation unless some means is found to
blank out transmission in an emergency. With split second timing at
stake, Mr. Flanders feels that an electronic pausing device is an urgent
priority.
Nearly every concert tour by a "super group" in recent years has had its origin at
Showco. We design and build the huge, high -level sound systems, intricate lighting and
special effects systems, and provide the stage
designs for over 1000 concerts a year. At the
conclusion of the tour, the tapes that we produce
have resulted in best -selling "live" albums.
Now, through Showco Manufacturing Corp., we
are bringing this same highly acclaimed expertise
into discotheque sound systems. We are in full
production of the S -2500 Disco Mixer, S -2501
Electronic Crossover Network, and our concert
proven Pyramid* 1000 and 900 speaker systems
designed to be suspended from the ceiling or to
be floor mounted with the optional base. Developments are underway for still other new and
¡
ÿf
innovative products. Call or write for the name of
your nearest dealer.
SOUND
The Pyramid speaker
incorporates a unique fully
symmetrical folded bass horn which in turn allows
the mid and hi frequency drivers to be optimally
mounted for wide dispersion. The overall result is a
single full range, high level, extremely efficient
catilnet ideally suited to discotheques.
SIlOWCO
MANUFACTURING
1226 Round Table Dve /DaI as,OTexaas5240N
Phone (214) 630 -7121
TWX (910) 861 -4278
Circle
11
on Reader Service Card
www.americanradiohistory.com
'U.S. Patent No. 3,912,866
Now there's a
JBL monitor specially
designed for
broadcast studios.
12'/6°
Fits on EIA
Standard Rack shelf.
Does your monitor
tell you about turntable rumble and
ambient noise (like
your air conditioning)
and tape hiss and
cue tone leakage?
The JBL 4301 will.
Our call letters.
If you're tuned into the
professional recording
studio business, you
know about JBL's
studio monitors.
If you're the station engineer or the jock on
duty, why should you be the last to know what
sound you're putting out?
Listen to the JBL 4301. It's a compact that
delivers wide band sound reproduction accuracy -the kind of accuracy your station is
going to need to keep up with the new broadcast standards.
Among other good things, the 4301 has
exceptional clarity, solid bass, open high frequency reproduction and a nice honest face.
If you'll fill out the coupon, we'll send you
a lot more specs and the name of your nearest
JBL Professional Products Dealer who would
be very glad to set up a test listening at your
convenience.
r
'AL
James B. Lansing Sound, Inc.
Professional Products Division
8500 Balboa Blvd.. Northridge, Calif. 91329
like what hear so far. Tell me more.
I
I
Name
Title
Station
Address
City
www.americanradiohistory.com
State
Zip
DB-8J
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