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CM-311A
CM-311AE
DIFFEROID HEAD-WORN
CONDENSER MICROPHONE
D
esigned for touring and live-sound applica-
tions, the Crown
®
CM-311A is a rugged
head-worn microphone with unequalled
performance. It sounds like the best handheld micro-
phones—full, clear, and distortion-free, even with the
loudest singers.
The CM-311A is the latest version of the Crown’s
proprietary Differoid
®
technology. Its cardioid pickup
pattern rejects sounds from the rear, such as fl oor
monitors. Its noise-canceling ability rejects sounds at
a distance, such as instruments on stage and crowd
noise. This results in the CM-311A having outstand-
ing gain-before-feedback and isolation.
Lightweight and comfortable, the mic’s headband and
boom adjust to fi t any singer. An included pop fi lter
greatly reduces breath noise and pops. Because of
the boom’s unique behind-the-ear design, it does not
cover up the singer’s face.
Two models are available: CM-311A and CM-311AE.
The CM-311A is powered by a 9V battery or phantom
power. It has a battery belt pack with an on/off switch,
a programmable mic on/off switch, and a “Mic On”
LED. The CM-311AE is a pig-tail version allowing you
to connect it to most wireless transmitters.
NOTE: Putting an XLR connector on the CM-311AE
and connecting to a mic input with phantom power
WILL damage the mic element. For wired applica-
tions, use the CM-311A.
How to adjust for best fi t and to prevent boom
bounce
Note: To get the maximum performance out of this
microphone, take the time to adjust it to fi t correctly.
For best results, the CM-311A MUST be custom fi tted
to a single user’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 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 bend the headband wire to fi t your head. Put
the foam-block wire behind your ear. Then you can
bend the earpieces to fi t snugly around your ears.
The back of the headband should fi t fi rmly against the
back of your neck.
Specifi cations
Transducer type: Electret condenser.
Frequency response (typical): 50 Hz to 17,000 Hz
(see Fig. 1).
Polar pattern: Cardioid (see Fig. 2).
Impedance: CM-311A, 75 ohms balanced. CM-311AE,
6 kilohms unbalanced.
Recommended load impedance: CM-311A, 1000
ohms or greater. CM-311AE, 10 kilohms.
Open-circuit sensitivity, typical, close-talking: CM-
311A, 4 mV/Pa* (–48 dB re 1V/Pa), CM-311AE,
1.25 mV/Pa (–58 dB re 1V/Pa).
Power sensitivity, typical, close-talking: CM-311A:
–42.5 dB re 1 mW/Pa*, CM-311AE: –71.5 dB re 1
mW/Pa.
Equivalent noise level (self noise): 26 dB SPL typi-
cal (0 dB = 0.0002 dyne/cm
2
), A-weighted.
S/N ratio: 68 dB at 94 dB SPL.
Maximum SPL: CM-311A, 148 dB SPL produces 3%
THD. CM-311AE, 140 dB SPL with 3V DC, 148 dB
SPL with 9V DC.
Operating voltage: CM-311A, 9V DC internal alkaline
battery or 18-48V phantom power. CM-311AE,
3–9V DC from the transmitter’s battery.
Polarity: Positive pressure on diaphragm produces
positive voltage on CM-311A XLR pin 2 with
respect to pin 3, and on CM-311AE shield with
respect to white lead.
Current drain: CM-311A, 6.5 mA nominal.
CM-311AE, 0.27 mA nominal.
Battery life: CM-311A, 85 hours. CM-311AE, approxi-
mately equal to transmitter battery life.
Operating temperature range: –10° to +50° C, or
–14° to +122° F.
Off-attenuation: 70 dB.
Output connectors: CM-311A, 3-pin pro audio (XLR
type). CM-311AE, supply your own to match your
transmitter.
Cables (CM-311A): 2-conductor shielded, unbalanced
cable, 42-inches (106.68 cm) from headband to
battery pack. Use 2-conductor shielded mic cable
(not included) between XLR connector and mixer
mic input.
Cable (CM-311AE): In-line with this cable is a small
circuit module that equalizes the microphone
signal. Cable is 42-inches (106.68 cm) long from
headband to module, 12-inches (30.48 cm) from
module to cable end. 2-conductor shielded unbal-
anced cable, unterminated.
Materials: High-impact plastic mic housing, brass
boom, steel wire headband, high-impact plastic and
steel battery pack.
Finish: Satin black.
Net weight: Head-worn mic, 2.1 oz (61 g). CM-311A
belt pack and battery, 6.1 oz (173g).
Dimensions: Headband 5.5-in. (13.97 cm) diameter,
adjustable. Boom approximately 7 in. (17.78 cm) x
3 in. (7.62 cm). See Figs. 3 and 4.
Included accessories: Microphone carrying case,
WS-6 foam pop fi lter, clothing clip.
Frequency in Hz
Frequency Response
Fig. 2
Fig. 1
MIC
Fig. 3
Polar Response
POLAR
PATTERN
Features
• Full, clear, distortion-free sound
• Outstanding gain-before-feedback and isolation
• CM-311A has battery/phantom belt pack
• CM-311AE connects to most wireless transmitters
Optional accessories: PH-1A phantom power
supply (1 channel, AC-adapter powered). WS-
14 accessory windscreen.
*1 pascal = 10 dynes/cm
2
= 10 microbars = 94 dB