AKG CM311 A, CM311 AESH, CM311 L Users Manual

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DIFFEROID® HEAD-WORN

CM311 A
CM311 AESH
CM311 L

esigned for touring and live-sound
applications, the AKG/Crown CM311

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 CM311 is the latest version of the
AKG/Crown’s proprietary Differoid

technology. Its cardioid pickup pattern
rejects sounds from the rear, such as floor
monitors. Its noise-cancelling ability rejects
sounds at a distance, such as instruments
on stage and crowd noise. This results in
the CM311 having outstanding gain-before­feedback 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.

Three models are available: CM311 A, CM311
AESH and CM311 L. The CM311 A is
powered by a 9 V 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 CM311 AESH has
a T4AF connector, allowing you to connect with
Shure® wireless systems. The L version offers a
3-pin mini XLR output, which fits all AKG wireless
body-pack transmitters.

How to adjust for best fit and to prevent
boom bounce

Note: To get the maximum performance out
of this microphone, take the time to adjust it
to fit correctly.

For best results, the CM311 A 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 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.

CONDENSER MICROPHONE

®

Specifications

Transducer type:
Frequency response (typical):

(see Fig. 1).

Polar pattern:
Impedance:

AESH and CM311 L, 6 kilohms unbalanced.

Recommended load impedance:

1000 ohms or greater. CM311 AESH and
CM311 L, 10 kilohms.

Open-circuit sensitivity, typical, close-talking:

CM311 A, 4 mV/Pa* (–48 dB re 1V/Pa),
CM311 AESH and CM311 L, 1.25 mV/Pa

(–58 dB re 1V/Pa).

Power sensitivity, typical, close-talking:

CM311 A: – 42.5 dB re 1 mW/Pa*, CM311
AESH and CM311 L: –71.5 dB re 1 mW/Pa.

Equivalent noise level (self noise):

SPL typical (0 dB = 0.0002 dyne/cm2),

A-weighted.

S/N ratio:
Maximum SPL:

3% THD. CM311 AESH and CM311 L, 140 dB
SPL with 3V DC, 148 dB SPL with 9V DC.

Operating voltage:

alkaline battery or 18-48 V phantom power.
CM311 AESH and CM311 L, 3-9 V DC from
the transmitter’s battery.

Polarity:

produces positive voltage on CM311 A XLR
pin 2 with respect to pin 3, and on CM 311
AESH and CM311 L shield with respect to
white lead.

Current drain:

CM311 AESH and CM311 L, 0.27 mA
nominal.

Battery life:

and CM311 L, approximately equal to
transmitter battery life.

Electret condenser.

Cardioid (see Fig. 2).

CM311 A, 75 ohms balanced. CM311

68 dB at 94 dB SPL.

CM311 A, 148 dB SPL produces

CM311 A, 9 V DC internal

Positive pressure on diaphragm

CM311 A, 6.5 mA nominal.

CM311 A, 85 hours. CM311 AESH

50 Hz to 17,000 Hz

CM311 A,

26 dB

Off

attenuation:

t connectors:

R type). CM311 AESH, TA4F for Shure®

s boom, steel wire headband, high-

:

Satin black.

Ne

weight:

-inch (17.78 cm) x 3-inch (7.62 cm).
Figs. 3 and 4.

d accessories:

, WS-6 foam pop filter, clothing clip.

-adapter powered). WS-14 accessory

*1

l = 10 dynes/cm2 = 10 microbars = 94 dB SPL.

70 dB.

CM311 A, 3-pin pro audio

. CM311 L, 3-pin mini XLR.

:

High-impact plastic mic housing,

t plastic and steel battery pack.

Head-worn mic, 2.1 oz (61 g).

A belt pack and battery, 6.1 oz (173g).

:

Headband 5.5-inch (13.97 cm)

r, adjustable. Boom approximately

Microphone carrying

l accessories:

y (4 channels, AC powered). PH-1A

m power supply (1 channel, battery or

PH-4B phantom power

Response

FRONT

0

5

10

15

20

REAR

180

Fig. 1

+15
+10

+5

dB 0

-5

-10

-15

-20

-25

-30

-35
20 100 1K

Frequency Response

0˚, 1.375"

0˚ 2'

120˚, 2'

Frequency in Hz

10K 20K

Fig. 2

300˚

270˚

240˚

Polar

330˚

0˚

-

-

-

-

-

30˚

60˚

90˚

120˚

1000 Hz

210˚

˚

300 Hz
6000 Hz

150˚

Fig. 3

MIC

Fig. 4

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headband

thumbscre

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defective, return the complete product in its

original packaging to one of the addresses

below

support call

[phone].

Fig. 5

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.

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.

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.

should press firmly against the lips.

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.

After several hours of use, the foam pop
filter can become clogged with moisture,

The foam pop filter

This

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 AKG’s Parts Department.

How to insert a battery in the CM311 A
belt pack

1. Access the battery by sliding open the
battery cover.

2. Insert a fresh 9V alkaline battery (Mallory
Duracell MN9100 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.

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:

*
*
*
To change the switch operation, open the belt-

pack case by removing the three screws. Set
the switch as shown below:

The LED lights when the mic is on.

Architects’ and Engineers’ Specifications

The microphone shall be the AKG/Crown
Model CM311 A or equivalent. The
microphone shall be a head-worn, noise­cancelling,

Push-on/push-off.
Momentary on.
Momentary off (as supplied).

d type of electret-condenser design.

Th

microphone shall exhibit excellent off-

axi

response and gain-before-feedback.

Th

microphone shall have an adjustable

, adjustable boom with locking

w, and foam pop filter.

l CM311 A shall include a battery belt

. In the CM311 A, a 42-inch,

y attached, two-conductor

d cable shall connect the micro-

e to the belt pack. The belt pack shall

e a 3-pin pro audio (XLR type) con-

r.

l CM311 A shall be powered by a 9 V

ry in the belt pack, or by 18 to 48 V

m power. The belt pack shall have a

ry on/off switch, a programmable mic

switch, and a “Mic On” LED.

l open-circuit sensitivity shall be 4

or

5 mV/Pa. Maximum SPL shall be

dB SPL for 3% THD. Equivalent noise

be 27 dBA nominal. Frequency

a

Se

Se

If
erl

shall be 50 Hz to 17,000 Hz with

off-axis response, over 20 dB

n at the rear null. The AKG/Crown

CM311 A is specified.

rophone Warranty

rown professional microphones are

ranteed unconditionally against
e years from date of original purchase.

rmation.

vice

, check that it is aimed correctly and is

from any cause for a period of

enclosed warranty sheet for additional

e microphone does not function prop-

d as described in this data sheet. If

determine that the microphone product is

. For further assistance or technical

the international helpdesk at

ACOUSTICS GMBH

AKG ACOUSTICS, U.S.

© 2015 HARMAN International Industries, Incorporated. All rights reserved.

Features, specifications and appearance are subject to change without notice.

CM

CM

CM311 L

TRIA

D, MORENO VALLEY, CA

AKG

United States and/or other countries.

www.akg.com

AKG

1

CM311 A Schematic

LAXENBURGER STRASSE 254, 1230 VIENNA/AUS

SERVICE 24950 GROVE VIEW ROA

AKG is a trademark of

311 A
311 AESH

92551, U.S.A

Acoustics GmbH, registered in the