Crown CM-312A Quick Reference

CM-312A
CM-312AE
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, incon-
spicuous 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 micro-
phone closer or farther from the corner of the mouth.
The CM-312A sounds like the best handheld micro-
phones. Its hypercardioid pickup pattern reduces
feedback and aids isolation. In diffi cult situations, the
Crown CM-311A headworn mic is recommended be-
cause it picks up even less feedback and leakage than
the CM-312A.
Designed for comfort, the headband fi ts behind the
head and disappears in use. Both the headband and
boom adjust to fi t 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 con-
nect it to a wireless transmitter of your choice. Crown
has some versions of the CM-312AE pre-wired with
connectors for various wireless systems, such as the
CM-312AESH for Shure wireless systems. Please ask
your local dealer or Crown Technical Support for more
information.
How to adjust for best fi t
For best results, the CM-312A MUST be custom fi tted
to one wearer's head. This simple procedure takes
only a few minutes. Please refer to Fig. 3 and locate
the parts described.
1. If the microphone is for yourself, we suggest that
you use a mirror to double check the fi t 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 adjust the headband to fi t your head. Put the
foam block wire behind your ear.
Start bending the headband wire from the boom
side, moving around to the other ear. The back of the
headband should fi t fi rmly against the back of the
neck. If you can slide a fi nger between the headband
and the back of your neck, then the headband is not
fi tted correctly. For users with smaller or petite heads,
you may have to re-bend the earpiece around the ear,
and cut off extra headband material.
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 foam-block wire. A snug fi t of the foam pad
prevents boom bounce when you move around.
POLAR
PATTERN
HYPERCARDIOID HEADWORN
CONDENSER MICROPHONE
Specifi cations
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, close-talking:
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/cm
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 bat-
tery 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, approxi-
mately 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 ca-
ble, 3-feet (0.915-m) from mic capsule to battery pack.
Use 2-conductor 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. 6 and 7.
Included accessories: Microphone carrying case, WS-7
foam pop fi lter and clothing clip for aerobics.
Optional accessories: PH-1A phantom power supply
(1 channel, battery or AC-adapter powered).
*1 pascal = 10 dynes/cm
2
), A-weighted.
2
= 10 microbars = 94 dB SPL.
Fig. 1
Frequency Response
+15
+10
0 0"
+5
dB 0
-5
-10
-15
0 2'
-20
-25
140 2'
-30
-35
-40
Frequency in Hz
Fig. 2
Polar Response
330 0
FRONT
-0
300
-5
-10
-15
-20
270
240
REAR
210 180 150
Fig. 3
EARPIECE
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
Fig. 4
30
60
90
120
200 Hz
300 Hz-3 kHz
10 kHz
MIC