Crown CM-311A Specifications

Crown CM-311A Specifications
esigned for touring and live-sound applications, the Crown® CM-311A is a rugged
head-worn microphone with unequalled
performance. It sounds like the best handheld microphones—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 floor
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 outstanding gain-before-feedback and isolation.
Lightweight and comfortable, the mic’s headband and
boom adjust to fit any singer. An included pop filter
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 applications, use the CM-311A.
How to adjust for best fit and to prevent boom
Note: To get the maximum performance out of this
microphone, take the time to adjust it to fit correctly.
For best results, the CM-311A MUST be custom fitted
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 fit as you make
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 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.
• 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
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: CM311A, 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
Equivalent noise level (self noise): 26 dB SPL typical (0 dB = 0.0002 dyne/cm2), 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, approximately 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
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 unbalanced 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 filter, clothing clip.
Optional accessories: PH-1A phantom power
supply (1 channel, AC-adapter powered). WS14 accessory windscreen.
*1 pascal = 10 dynes/cm2 = 10 microbars = 94 dB
Fig. 1
Frequency Response
Frequency in Hz
Fig. 2
Polar Response
Fig. 3
Fig. 4
After several hours of use, the foam pop filter can become clogged with moisture, giving a muffled sound.
Periodically wash it in mild detergent and water. The
foam pop filter is held in place by a removable ring.
Additional WS-6 pop filters can be ordered from
Crown’s Parts Department.
How to insert a battery in the CM-311A belt pack
1. Access the battery by sliding open the battery cover.
2. Insert a fresh 9V alkaline battery (Mallory Duracell
MN1604 or equivalent) into the battery tray. The battery cover shows the correct polarity.
3. Replace the battery cover. To prolong battery life,
turn off the battery switch when not in use.
Fig. 5
If you’re using phantom power, and the battery switch
is on, the battery will take over automatically if phantom power fails.
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:
* Push-on/push-off.
* Momentary on.
* Momentary off (as supplied).
To change the switch operation, open the belt-pack
case by removing the three screws. Set the switch as
shown below:
phone alone. In the CM-311A, a 42-inch, 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.
In the CM-311AE, a 42-inch, permanently attached,
two-conductor shielded cable can be connected to a
Model CM-311A shall be powered by a 9V battery in
the belt pack, or by 18 to 48V phantom power. The
belt pack shall have a battery on/off switch, a programmable mic on/off switch, and a “Mic On” LED.
Model CM-311AE shall be powered by 3–9V DC from
a transmitter.
Nominal open-circuit sensitivity shall be 4 or 1.25
mV/Pa. Maximum SPL shall be 148 dB SPL for 3%
THD. Equivalent noise shall be 27 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
null. The Crown models CM-311A and CM-311AE are
Microphone Warranty
Crown professional microphones are guaranteed
against malfunction for a period of three years from
date of original purchase. See enclosed warranty sheet
for additional information.
The LED lights when the mic is on.
How to connect the CM-311AE to a wireless transmitter
Note: For users with petite heads, extra headband
material may have to be cut off to get the headband to
fit properly.
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 fit of the foam
pad prevents boom bounce when you move around.
5. Be sure that the thumbscrew is still loosened a
little. Move the boom in or out, and left or right, to
center the mic directly in front of your lips. The foam
pop filter should press firmly against the lips. This
is necessary because the mic cancels sounds that are
not close to it. Also, it keeps the boom from bouncing.
Tighten the thumbscrew and you’re done.
Once you’ve adjusted the headset, it should remain
in that position -- no further adjustments are needed.
You can still swing the mic up or down, away from
your lips, if you don’t want to be heard on the P.A.
— or use the mic on/off switch programmed for
“press off” operation.
1. Solder on a connector that mates with your transmitter. Technical Bulletin #3 (included) shows the
correct wiring for various transmitters. A wireless
transmitter must have separate leads for ground,
audio and bias (3-9 volts).
2. Plug in the cable. Adjust the trim pot on the transmitter input to prevent distortion.
If the microphone does not function properly, check
that it is aimed correctly and is connected as
described in this datasheet. If the microphone is
defective, return it in the original packaging to: Crown
Factory Service, 1718 West Mishawaka Road,
Elkhart, IN 46517-9439.
A Service Return Authorization (SRA) is required
for product being sent to the factory for service. An
SRA can be completed on line at www.crownaudio.
com/support/factserv.htm. For further assistance or
technical support call 800-342-6939.
Note: Crown has certain models available for wireless
transmitters from Shure, AKG, Audio-Technica and
Telex. Contact Technical Support for more information
at 800-342-6939.
Architects’ and Engineers’ Specifications
The microphone shall be the Crown Model CM-311A
or CM-311AE or equivalent. The microphone shall be
a head-worn, noise-cancelling, cardioid type of electret-condenser design. The microphone shall exhibit
excellent off-axis response and gain-before-feedback.
The microphone shall have an adjustable headband,
adjustable boom with locking thumbscrew, and foam
pop filter.
Model CM-311A shall include a battery belt pack.
Model CM-311AE shall be the head-worn micro-
Crown International, Inc.
1718 W. Mishawaka Rd.
Elkhart, IN 46517-9439
TEL: 574-294-8000
FAX: 574-294-8FAX
© 2008 Crown Audio®, Inc. Specifications subject to
change without prior notice. Latest information avalable at Crown, Crown Audio and Differoid
are registered trademarks of Crown International.
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