Electro-Voice Michigan MC12A, MC8A & MC12A User manual

Electro-Voice Michigan MC12A, MC8A & MC12A User manual
Frequency Response in Recommended
Vented Enclosure, 1 Meter on Axis,
Half-Space Anechoic Environment,
Swept One-Third-Octave Random
Noise, 4 6 dB
MC8A — 42-20,000 Hz
MC12A — 32-11,000 Hz
Low-Frequency Acoustic Power Output
vs. Frequency, Small Signal, in
Recommended Vented Enclosure
MC8A — 50 Hz
MC12A — 40 Hz
MCSA — 37 Hz
MC12A — 27 Hz
Sound Pressure Level at 1 Meter, 1 Watt
into Nominal Impedance, Anechoic
Environment, 300-2,000 Hz Average
MCBA — 97 dB
MC12A — 97 dB
Power Handling Capacity
Long-Term Average
MCSA — 12 watts
MC12A — 20 watts
Short-Term (10 milliseconds)
MC8A — 120 watts
MC12A — 200 watts
Half-Space Reference Efficiency
MCBA — 1.35%
MC12A — 1.35%
Amplifier Power Requirements,
Continuous Average at 8 Ohms, for the
Following Average Sound Pressure
Levels, Mid-Band, in the Reverberant
Field of a Typical Living Room
(R=200) with Peaks 10 dB above
Average (Long-Term Average Power
Capacity not to be exceeded)
Medium Level (85 dB SPL)
MCSA — 1 watt
MC12A — 1 watt
Loud Level (85 dB SPL)
MCSA — 10 watts
MC12A — 10 watts
Very Loud Level (105 dB SPL)
MCBA — 100 watts
MC12A — 100 watts
Maximum Level
MCSA — 120 watts (106 dB)
MC12A — 200 watts (108 dB)
MC8A — 8 ohms
MC12A — 8 ohms
MCSA — 7.5 ohms
MC12A — 8 ohms
Thiele-Small Driver Parameters,
Nominal (see Special Note on Low-
Frequency Performance section)
Free-Air Resonance Frequency
MCBA — 75 Hz
MC12A — 50 Hz
Electro-Magnetic O at fg
MCBA — 0.87
MC12A — 1.2
Mechanical Q at fg
MCBA — 1.95
MC12A — 2.2
Qrs a o
Toral Cat tg | ___ DE
2 [as + Qms
МСВА — 0.60
MC12A — 0.78
Volume of Air Having Same
Acoustic Compliance as Driver
MCSA — 1.05 f13
MC12A — 5.1 НЗ
Half-Space Reference Efficiency
MCBA — 1.35%
MC12A — 1.35%
Peak Displacement Valume of
Diaphragm ( = Sp X max)
MC8A — 1.9 in3
MC12A — 4.7 in3
Effective Diaphragm Area
MCSA — 30 in
MC12A — 75 in2
a MARK IV company
Peak Linear Displacement of
MCSA — 0.083 in
MC12A —0.063 in
Thermally Limited Maximum Input
MCBA — 12 watts
MC12A — 20 watts
DC Resistance of Voice Coil
MCSA — 6.5 ohms
MC12A — 7.5 ohms
Cone Diameter, Nominal
MC8A — 8 in
MC12A — 12 in
Voice Coil Diameter
MC8A — 1 in
MC12A — 2 in
Magnet Weight
MC8A — 10 oz
MC12A — 13 oz
Magnet Material
MC8A — ceramic
MC12A — ceramic
Overall Diameter
MCSA — 8-1/4 in
MC12A — 12-1/4 in
Overall Depth
MCSA — 3-3/16 in
MC12A — 3-1/2 in
Mounting Bolt Circle
MCBA — 7-5/8 in
MC12A — 118/16 in
Mounting Hole Diameter, Four Evenly
Spaced Holes
MC8A — 7/32 in
MC12A — 0.28 in
Baffle Opening Diameter
(Note: Frame does not permit front
MCBA — 7 in
MC12A — 11 in
Net Weight
MC8A — 4 16, 2 о2
MC12A — 5 6,7 oz
Electro-Voice component speakers have
traditionally provided the hobbyist and
professional with the flexibility of
custom installation as well as the oppor-
tunity for simple “building-block”
system expansion and improvement. A
comprehensive group of cone speakers,
mid-fregquency horns and drivers, horn
tweeters, crossovers, and accessories is
available. Additionally, all Electro-Voice
component speakers offer conversion
efficiencies substantially higher(3 to 8
dB) than typical “bookshelf” home
speaker systems. This high efficiency is
essential for most professional audio
applications. In the home it permits
accurate reproduction of the high sound
levels of live music or, for more normal
listening levels, the use of amazingly
small amplifiers for satisfactory
Electro-Voice cone speakers have now
been thoroughly revised to reflect the
latest knowledge of rational, optimized
low-frequency speaker enclosure design.
The result is a combination of extended
low-distortion bass response, high
efficiency, and modest cabinet size
simply not available in other component
The Michigan? MCSA and MC12A
speakers are designed to provide full-
range high-fidelity reproduction at
modest cost. Both speakers are appro-
priate for home music systems and the
smaller MC8A may be used com-
mercially in high-quality ceiling
mounted sound systems.
High-frequency output is enhanced by a
centrally mounted free-edge cone whose
dimensions and mass have been care-
fully chosen for maximum performance
improvement. The free-edge cone is
small and light so it is able to respond to
the extremely rapid high-frequency
motions of the voice coil which the
large main cone cannot follow. The
MCBA and MC12A have die-cast frames
which offer long-term stability not
found in stamped-frame speakers. Also,
the MCBA's frame is drilled to accept
Electro-Voice TM5, TR5, and TR15
line-matching transformers.
The characteristics of both speakers
have been carefully developed to work
well in vented (bass reflex) enclosures of
small or reasonable size. In the recom-
mended 2.4 cubic feet vented enclosure
the MCBA provides essentially flat
response to 50 Hz with usable output
down to 37 Hertz. The larger MC12A,
in its recommended 6 cubic feet
enclosure, has essentially flat response
to 40 Hz with usable output to below
ЗО Hz. In addition, the MCSA may be
housed in the small sealed ceiling-
mounted boxes used in commercial
The MC8A and MC12A have been
designed for mounting in vented boxes
appropriate to the speaker charac-
teristics. The use of a vented box with
its tuned feature complements the per-
formance of the speaker and provides
maximum low-frequency performance
consistent with size and speaker para-
meters. A vented box not only increases
the low-frequency power output but
also reduces distortion for a given level,
The MC8A may also be used in the
small sealed enclosures found in ceiling-
mounted distributed speaker systems.
When used in this way low-frequency
performance is considerably reduced
but is usually adequate for commercial
In the listing below we have attempted
to choose a typical vented box size that
best complements the MC8A and
MC12A. Other vented box sizes and
tunings are quite feasible and may give
performance more suitable for a partic-
ular application. Two small sealed
enclosures for the MCBA are also
shown. For further information refer to
the Special Note on Low-Frequency
Performance section of this sheet and
ask for a copy of Bulletin 10B.
Explanation of Symbols:
Vg Net internal enclosure volume, not
including volume displaced by
bracing, port, or speaker.
Variations of + 10% are acceptable.
fg Helmholtz resonance frequency of
box-vent combination.
fa Frequency at which the small signal
(normal listening levels) acoustic
power vs. frequency is down 3 dB
relative to the mid-band output.
f1p Frequency at which the small signal
(normal listening levels) acoustic
power vs. frequency is down 10 dB
relative to the mid-band output.
fi Usable low-frequency limit, the
frequency at which the large-signal
maximum acoustic power output
vs. frequency is 10 dB below the
maximum mid-band output (due to
either thermal or displacement
Dimensions for the two recommended
vented enclosures are shown below:
MCSA — 2.4 ft3
MC12A — 6 ft3
Inside Depth (D)
MC8A — 13 in
MC12A — 17-5/16 in
Inside Width (W)
MC8A — 16-1/4 in
MC12A — 21-13/16 in
Inside Height (H)
MC8A — 20-3/4 in
MC12A — 27-1/2 in
Port Area (XY)
MCSA — 12 in2
MC12A — 16 in?
Port Depth (L)
MC8A — 2-3/4 in
MC12A — 4-3/4 in
Enclosure Vg Тв fa f10 fLL
Unit Type (ft3) (Hz) (Hz) (Hz) (Hz)
MCSA Sealed 0 120 88 88
MCBA Sealed 1 0 92 58 80
MCEA Vented 2.4 50 50 37 43
MCIZA Vented © 40 40 27 34
An outline drawing of a typical
enclosure is shown below.
Speaker enclosures should be con-
structed of rigid materials such as void-
free plywood or particle board. In
general, 3/4-inch thick material is most
satisfactory, although smaller enclosures
(approximately 2 cubic feet and under)
may be successfully constructed of
5/8-inch material. It is mandatory that
the joints between the pieces of wood
be strong and well sealed. Simple butt
joints secured with wood screws or nails
and white glue are very satisfactory.
Removable panels should be secured
with wood screws and weather stripping
tape. For joints longer than about 3
feet, internal glue blocks may be
appropriate. In the largest boxes—
greater than about 6 cubic feet—bracing
is usually required for the largest
expanses of wood to prevent
sympathetic vibrations from affecting
overall system performance. Proper
bracing technique splits a rectangular
panel into two equal rectangles with the
brace placed along the panel's longest
dimension. Good bracing materials are
2 X 2 dimension lumber or 4-inch widths
of 3/4-inch plywood, placed on edge.
Three mutually adjacent inside surfaces
of the enclosure (top, one side and rear)
should be lined with a one to two inch
thickness of glass wool or similar
acoustic absorptive material to prevent
internal reflections from affecting mid-
frequency performance. No absorptive
material should be placed over or within
the port.
The location of the speaker on the
mounting baffle is relatively unimpor-
tant but close-to-ear-level mounting will
provide best mid- and high-frequency
performance in the listening room. The
enclosure's height, width, and depth
may be changed as long as (1) the
internal volume remains the same
(+ 10%) and (2) extreme differences
between any two dimensions are
avoided. The required port area can be
obtained by any convenient combi-
nation of width (Y) and height (X) as
long as its long dimension is no more
than five times the short dimension. The
port is normally located on the front
baffle board but may also be on any
other box surface that has free access to
the listening room. For most accurate
box tuning the port should be no closer
than several inches from the nearest
adjacent enclosure wall. The port's
proximity to the speaker is
The MCBA and MC12A are designed for
installation on the inside surface of the
mounting baffle. As with all quality
speakers care should be taken in
mounting if best results are to be
obtained. Drill four mounting holes and
cut the mounting baffle opening in
accordance with the dimensions given in
the Specifications section. To mount
the speaker, four carriage bolts with
nuts and washers may be used. The
MCSA frame will accommodate a
3/16-20 bolt and the MC12A will
accommodate a 1/4-20 bolt. Wocd
screws are not recommended. Secure
the speaker to the baffle board just
tightly enough to compress the speaker
gasket. Excessive tightening is not neces-
sary since the compressible gasket will
forma satisfactory seal with only
nominal pressure.
To avoid any significant amplifier power
loss in the speaker lines and undesirable
change in low-frequency response, wire
size must be properly chosen. 18 gauge
stranded wire (commonly called lamp or
"zip" cord) is satisfactory for lengths up
to 38 feet, limiting the loss in sound
pressure level to an insignificant 0.5 dB.
If longer speaker lines are required, use
progressively larger wire sizes: 16 gauge
to 60 feet, 14 gauge to 96 feet, and 12
gauge to 150 feet. These lengths assume
the 8-ohm impedance of one speaker.
Two speakers in parallel have an imped-
ance of 4 ohms, so if connected to the
end of a single speaker line the lengths
listed above must be halved. If it is
desired to run the speaker line under a
carpet TV twin lead may be used for
short distances.
Transformer Installation (MCBA)
For constant-voltage distribution
systems an Electro-Voice TM5, TR5, or
TR 15 line-matching transformer may be
directly mounted on the MCBA frame
using the holes provided with two 6-32
x 1/4 self-tapping screws.
While both the MCBA and MC12A will
provide quite adequate sound repro-
duction under most circumstances, an
improvement in performance can easily
be realized by adding a tweeter and
mid-frequency speaker.
The tweeter will provide the most
dramatic improvement and should be
added first through the use of an HF1
High-Frequency Building Block Kit. The
HF1 includes a TW35 horn tweeter,
CR35 crossover/level control, wiring
harness, and mounting hardware. In
addition to extending the high-
frequency response beyond the limits of
normal audibility, the HF 1 provides
more precise definition of high-
frequency wave forms and much
improved high-frequency dispersion in
the listening area. The improved disper-
sion makes it possible for the listener to
move considerably off the central axis
while experiencing very little change in
sound quality.
The MF1 Mid-Frequency Building Block
Kit, comprised of an MR 10 horn/driver,
CR 10 crossover/level control, wiring
harness, and mounting hardware,
provides additional improvement in
performance after installation of the
HF1. The MF1 further reduces the fre-
quency range which must be reproduced
by the cone speaker, reducing harmonic
and intermodulation distortion in the
system, The MR 10's diffraction horn
improves dispersion in the listening area
in addition to increasing efficiency. The
improved mid-frequency performance
provided by the MF1 is especially
important because instrument and voice
harmonics which determine the char-
acter of the sound are found in this
frequency range.
The recommended enclosures and
associated performance specifications
displayed earlier were determined in
accordance with the definitive analysis
о? А. М. Thiele, BR. H. Small, and others.
The performance of speakers in sealed
enclosures (including acoustic sus-
pension types) has been well understood
for some time. In contrast, vented
systems have been designed using not
much more than cut-and-try methods
with little real engineering know-how.
However, the above mentioned analysis
has changed this picture completely.
Thiele showed the similarity between a
speaker in an enclosure and an electrical
high-pass filter circuit. Application of
well known filter analysis techniques led
to quite accurate performance calcu-
lations for any speaker mounted in any
vented or sealed cabinet. Moreover, it
was shown that a properly executed
speaker /vented-enclosure combination
held clear-cut advantages over a sealed
system in the areas of efficiency, box
size, low-frequency limit, and distor-
tion. These results make the choices of
box size, low-frequency limit,
efficiency, power-handling capacity, and
maximum acoustic power output rela-
tively easy to make. In fact, Thiele even
presented in tabular form quite a
number of possible vented box choices
having optimum performance charac-
teristics (see A. N. Thiele, “Loud-
speakers in Vented Boxes: Part |”
J. Audio Eng. Soc., Vol. 19,
May 1971, p. 388)
By applying the work of Thiele and
small, Electro-Voice engineers
developed a computer program which
easily, quickly, and accurately predicts
the performance of any speaker-box
system in the frequency range where the
diaphragm is acting as a simple piston.
The upper limit for this operation is
usually the frequency at which the dia-
meter of the diaphragm becomes a large
traction of a wavelength.
The Thiele-Small Driver Parameters
shown in the Specifications section
include the speaker characteristics re-
quired by the computer program to
develop the small and large signal per-
formance of a given speaker and
enclosure combination.
For more information on this subject,
ask for Bulletin 10B. It includes addi-
tional vented enclosure recom-
mendations for Electro-Vaice
component speakers and a detailed
bibliography of the work of Thiele,
Small, and others. Also, where the
Thiele-Small Driver Parameters are
known, Bulletin 10B shows how to
choose the size and tuning of a vented
enclosure and how to determine the
low-frequency response of vented and
sealed speaker systems using scientific
pocket calculators.
WARRANTY (Limited) —
Electro-Voice High Fidelity Speakers
and Accessories are guaranteed for five
years from date of original purchase
against malfunction due to defects in
workmanship and materials. If such
malfunction occurs, unit will be re-
paired or replaced (at our option) with-
out charge for materials or labor if
delivered prepaid to the proper
Electro-Voice service facility. Unit will
be returned prepaid. Warranty does not
cover finish or appearance items or mal-
function due to abuse or operation at
other than specified conditions. Repair
by other than Electro-Voice or its
authorized service agencies will void this
For correct shipping address,
instructions on return of Electro-Voice
products for repair, and locations of
authorized service agencies, please
write: Service Department,
Electro-Voice, Inc., 600 Cecil Street,
Buchanan, Michigan 49107 (Phone:
Electro-Voice also maintains complete
facilities for non-warranty service of
E-V products.
Specifications subject to change
without notice.
a MARK IV company.
ELECTRO-VOICE, INC., 600 Cecll Street, Buchanan, Michigan 49107
© Electro-Voice, Inc. 1987 MW Litho In USA.
Part Number 53013—613
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