CM-312A
CM-312AE
HYPERCARDIOID HEAD-WORN
CONDENSER MICROPHONE
T
he Crown CM-312A is a rugged,
lightweight head-worn microphone
designed for aerobics, live entertainment, and sports broadcasting. It is intended for applications that require a
light, inconspicuous mic.
Because the microphone is to the side of
the mouth, breath pops are eliminated. The
sound of the CM-312A can be tailored to
taste by moving the microphone closer or
farther from the corner of the mouth.
The CM-312A sounds like the best handheld
microphones. Its hypercardioid pickup
pattern reduces feedback and aids isolation.
In difficult situations, the Crown CM-311A
headworn mic is recommended because it
picks up even less feedback and leakage
than the CM-312A.
Designed for comfort, the headband fits
behind the head and disappears in use. Both
the headband and boom adjust to fit any
head. Because of the boom’s unique behind-the-ear design, it does not cover up the
user’s face.
Two models are available: CM-312A and
CM-312AE. The CM-312A is powered by a
9V battery or phantom power. It has a
battery belt pack with a battery on/off
switch, a programmable mic on/off switch,
and a “Mic On” LED. The CM-312AE has no
connector; you connect it to a wireless
transmitter of your choice.
How to adjust for best fit
For best results, the CM-312A MUST be
custom fitted to one wearer’s head. This
simple procedure takes only a few minutes.
Please refer to Fig. 5 and locate the parts
described.
1. If the microphone is for yourself, we
suggest that you use a mirror to double
check the fit as you make adjustments.
2. Loosen (just a little) the thumbscrew
located on the outside of the foam block,
part way back on the boom. This allows the
boom to slide in and out, and to rotate left
and right.
3. Now bend the headband wire to fit your
head. Put the foam-block wire behind your
Specifications
Transducer type: Electret condenser.
Frequency response (typical): 50 Hz to
17,000 Hz (see Fig. 1).
Polar pattern: Hypercardioid (see Fig. 2).
Impedance: CM-312A, 75 ohms balanced.
CM-312AE, 6 kilohms unbalanced.
Recommended load impedance: CM-312A,
1000 ohms or greater. CM-312AE, 10
kilohms.
Open-circuit sensitivity, typical, closetalking: CM-312A, 3.8 mV/Pa* (–48.5 dB re
1V/Pa), CM-312AE, 2.9 mV/Pa (–51 dB re
1V/Pa).
Power sensitivity, typical, close-talking:
CM-312A: –43 dB re 1 mW/Pa*.
CM-312AE: –65 dB re 1 mW/Pa.
Equivalent noise level (self noise): 31 dB
SPL typical (0 dB = 0.0002 dyne/cm2),
A-weighted.
S/N ratio: 63 dB at 94 dB SPL.
Maximum SPL: 148 dB SPL produces 3%
THD.
Operating voltage: CM-312A, 9V DC internal
alkaline battery or 18-48V phantom power.
CM-312AE, 3–9V DC from the transmitter’s
battery.
Polarity: Positive pressure on diaphragm
produces positive voltage on pin 2 with
respect to pin 3, and on CM-312AE white
lead with respect to shield.
Current drain: CM-312A, 6 mA nominal.
CM-312AE, 0.27 mA nominal.
Battery life: CM-312A, 90 hours. CM-312AE,
approximately equal to transmitter battery
life.
Off-attenuation: 70 dB @ 1kHz.
Output connectors: CM-312A, 3-pin pro audio
(XLR type). CM-312AE, supply your own to
match your transmitter.
Cables (CM-312A): 2-conductor shielded,
unbalanced cable, 3-feet (0.915-m) from
mic capsule to battery pack. Use 2conductor shielded mic cable (not included)
between XLR connector and mixer mic
input.
Cable (CM-312AE): 45-inches long (1.144-m),
2-conductor shielded unbalanced cable,
unterminated. In-line with this cable is a
small circuit module that equalizes the
microphone signal.
Materials: High-impact plastic and PVC mic
housing, brass boom, steel wire headband,
high-impact plastic and steel battery pack.
Finish: Satin black.
Net weight: Head-worn mic, 1.5 oz (43 g).
CM-312A belt pack and battery, 6.1 oz
(173 g).
Dimensions: Headband 5.5 in. (13.97 cm)
diameter, adjustable. Boom approximately
5.75 in. (14.61 cm). See Figs. 3 and 4.
Included accessories: Microphone carrying
case, WS-7 foam pop filter and clothing clip
for aerobics.
Optional accessories: PH-4B phantom power
supply (4 channels, AC powered). PH-1A
phantom power supply (1 channel, battery
or AC-adapter powered).
*1 pascal = 10 dynes/cm2 = 10 microbars = 94 dB SPL.
Fig. 1
Fig. 4
Frequency Response
Dimensions, Battery Pack
+15
+10
0˚, 1.375"
+5
dB 0
-5
-10
-15
0˚ 2'
-20
-25
120˚, 2'
-30
35
Frequency in Hz
Fig. 2
330˚
0˚
30˚
FRONT
-0
300˚
60˚
-5
-10
-15
-20
270˚
90˚
Fig. 5
240˚
1000 Hz
300 Hz
6000 Hz
120˚
EARPIECE
REAR
210˚
Fig. 3
180˚
Dimensions
150˚
HEADBAND
WIRE
FOAM BLOCK
WIRE
BOOM
FOAM BLOCK
THUMBSCREW
DETAIL
TO MOVE MIC
UP OR DOWN
TO MOVE MIC
IN OR OUT
TO MOVE MIC
LEFT OR RIGHT
MIC
ear. Then you can bend the earpieces to fit
snugly around your ears. The back of the
headband should fit firmly against the back
of your neck.
How to insert a battery in the CM-312A belt
pack
1. Access the battery by sliding open the
battery cover.
Fig. 6
4. Next, adjust the foam pad snug against
your head or neck. To do this, bend the wire
that goes into the foam block. CAUTION!
Do not bend the boom itself – just the foamblock wire. A snug fit of the foam pad
prevents boom bounce when you move
around.
2. Insert a fresh 9V alkaline battery (Mallory
Duracell MN9100 or equivalent) into the
battery tray. The battery cover shows the
correct polarity.
5. Be sure that the thumbscrew is still loosened a little. Position the mic to the side of
your mouth, about 1-inch (2.54 cm) in
front. To do this, move the boom in or out,
and left or right. Move the mic up or down
by bending the foam-block wire.
If you’re using phantom power, and the battery
switch is on, the battery will take over automatically if phantom power fails.
3. Replace the battery cover. To prolong battery life, turn off the battery switch when not in
use.
After 85 hours of use, or if the sound is distorted, it’s time to replace the battery.
How to program the mic on/off switch
The mic on/off switch can be programmed to
work in three ways:
Changing the mic position changes the ratio
of lows to highs. Adjust the position for the
sound you prefer. If you hear breath pops,
move the mic farther to the side of your
mouth (Fig. 5). Tighten the thumbscrew.
* Push-on/push-off (as supplied).
* Momentary on (push to talk).
* Momentary off (cough button).
Once you’ve adjusted the headset, it should
remain in that position – no further adjustments are needed.
To change the switch operation, open the beltpack case by removing the three screws. Set
the switch as shown below:
When using the mic for aerobics, you’ll
need to keep the cable in place. To do this,
attach the cable to the clothes clip (included), and clip it to the back of your shirt.
As shown in Fig. 6, be sure that the cable
droops BELOW the clip. That way, sweat
drips off the cable instead of into the electronics.
TO XLR
S3
BT1
9V
VCC
W10
MOM. ON
(P.T.T.)
MOM OFF
(COUGH)
PUSH ON/
PUSH OFF
Additional WS-7 foam pop filter and clothing
clips can be ordered from Crown’s Parts
Department.
W5
W6
D3
RED
C9
FB1
C8
W3
WHT
R13
3
2
SHIELD
R29
R15
C6
8
U3A
1
C12
R22
4
R14
U4
3
C17
R24
W4
Q3
MICROPHONE CAPSULE
VCC
R16
VCC
R12
Q4
C10
R19
R6
5
U2A
14 6
5
1
3 D S Q
CLK
2
R Q
C15
C1
C3
4
7
R3
WHT W9
Q5
Q1
C7
R17
C19
R18
R26
R21
E1
R8
5
6
U3B
7
C13
R23
R11
W2
3
1
U1A
2
U1E
5
U1B
4
11
8
C16
C11
R4
R5
R1
D1
7
6
U1C
9
U1D
10
Q2
12
R9
4 3 2
1
S2
MICROPHONE ELECTRONICS
CM-312A Schematic
SHIELD W8
R28
VCC
R7
D4
C14
R25
R20
S1
6
C4
R2
C2
GRN W7
R27
7
R10
C5
W1
2
1
4
CM-312A
CM-312AE
How to connect the CM-312AE to a wireless
transmitter
1. Solder on a connector that mates with your
transmitter. Technical Bulletin #3 (included)
shows the correct wiring for various transmitters.
2. Plug in the cable. Adjust the trim pot on the
transmitter input to prevent distortion.
Architects’ and Engineers’ Specifications
The microphone shall be the Crown Model
CM-312A or equivalent. The microphone shall
be a head-worn hypercardioid type of electretcondenser design. The microphone shall
exhibit excellent off-axis response and gainbefore-feedback. The microphone shall have
an adjustable headband, adjustable boom with
locking thumbscrew, and foam pop filter.
Model CM-312A shall include a headworn mic
and a battery belt pack. Model CM-312AE
shall be the head-worn microphone alone. In
the CM-312A, a 3-feet (0.915-m), permanently
attached, two-conductor shielded cable shall
connect the microphone to the belt pack. The
belt pack shall include a 3-pin pro audio (XLR
type) connector, a battery on/off switch, a
programmable mic on/off switch, and a “Mic
On” LED. In the CM-312AE, a 45-inch (1.144m), permanently attached, two-conductor
shielded cable can be connected to a transmitter.
The CM-312A shall be powered by a 9V battery in the belt pack, or by 18 to 48V phantom
power. The CM-312AE shall be powered by
3–9V from a transmitter.
Nominal open-circuit sensitivity shall be 3.8
mV/Pa. Maximum SPL shall be 148 dB SPL
for 3% THD. Equivalent noise shall be 31 dBA
nominal. Frequency response shall be 50 Hz to
17,000 Hz with a uniform off-axis response,
over 20 dB down at the rear nulls. The Crown
models CM-312A and CM-312AE are specified.
closed full warranty statement for more detail.
Service
If the microphone does not function properly, check that it is aimed correctly and is
connected as described in this data sheet.
If the microphone is defective, return it in
the original packaging to: Crown Service
Department, Plant 2 SW, 1718 West
Mishawaka Road, Elkhart, IN 46517. For
further assistance or technical support call
800-342-6939.
Warranty
Crown professional microphones are guaranteed unconditionally against malfunction from
any cause for a period of three years from date
of original purchase. Please refer to the en-
+
+
+
CM-312AE Schematic
Crown Audio, Inc.
P. O. Box 1000
Elkhart, IN 46515-1000
TEL: 219-294-8000
FAX: 219-294-8FAX
www.crownaudio.com
©2000 Crown Audio, Inc.
Specifications subject to change without prior notice.
Latest information available at www.crownaudio.com.
Crown® is a registered trademark of Crown International, Inc.
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