AKG DIFFEROID CM311 A User manual

D
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-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.
Threemodels 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-packtransmitters.
How to adjust for best fit and to prevent
boombounce
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.
DIFFEROID
®
HEAD-WORN
CONDENSER MICROPHONE
Specifications
Transducer type: Electret condenser.
Frequency response (typical): 50 Hz to 17,000 Hz
(see Fig. 1).
Polar pattern: Cardioid (see Fig. 2).
Impedance: CM311 A, 75 ohms balanced. CM311
AESH and CM311 L,6kilohmsunbalanced.
Recommended load impedance: CM311 A,
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): 26 dB
SPL typical (0 dB = 0.0002 dyne/cm2),
A-weighted.
S/N ratio: 68 dB at 94 dB SPL.
Maximum SPL: CM311 A, 148 dB SPL produces
3% THD. CM311 AESH and CM311 L, 140 dB
SPL with 3V DC, 148 dB SPL with 9V DC.
Operating voltage: CM311 A, 9 V DC internal
alkaline battery or 18-48 V phantom power.
CM311 AESH and CM311 L, 3-9 V DC from
the transmitter’s battery.
Polarity: Positive pressure on diaphragm
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 A, 6.5 mA nominal.
CM311 AESH and CM311 L, 0.27 mA
nominal.
Battery life: CM311 A, 85 hours. CM311 AESH
and CM311 L, approximately equal to
transmitter battery life.
Off
-
Outpu
(XL
wireless systems
Materials
bras
impac
Finish
Ne
t
CM311
Dimensions
diamete
7
See
Include
case
Optiona
suppl
phanto
AC
windscreen.
*1
pasca
-
attenuation: 70 dB.
Outpu
t connectors: CM311 A, 3-pin pro audio
(XL
R type). CM311 AESH, TA4F for Shure®
wireless systems
. CM311 L, 3-pin mini XLR.
Materials
: High-impact plastic mic housing,
bras
s boom, steel wire headband, high-
impac
t plastic and steel battery pack.
Finish
: Satin black.
weight: Head-worn mic, 2.1 oz (61 g).
CM311
A belt pack and battery, 6.1 oz (173g).
Dimensions
: Headband 5.5-inch (13.97 cm)
diamete
r, adjustable. Boom approximately
7
-inch (17.78 cm) x 3-inch (7.62 cm).
See
Figs. 3 and 4.
Include
d accessories: Microphone carrying
case
, WS-6 foam pop filter, clothing clip.
Optiona
l accessories: PH-4B phantom power
suppl
y (4 channels, AC powered). PH-1A
phanto
m power supply (1 channel, battery or
AC
-adapter powered). WS-14 accessory
windscreen.
pasca
l = 10 dynes/cm
2
= 10 microbars = 94 dB SPL.

Fig. 1
Frequency Response
+15
+10
+5
dB 0
-5
-10
-15
-20
-25
-30
-35
0˚, 1.375"
0˚ 2'
120˚, 2'
20 100 1K
Frequency in Hz
Fig. 3
MIC
Fig. 2
Polar
Response
300˚
270˚
240˚
330˚ 0˚
FRONT
-
0
-
5
-
10
-
15
-
20
10K 20K
210˚
REAR
180
Fig. 4
Response
30˚
FRONT
0
5
10
15
20
60˚
90˚
120˚
REAR
180
˚
150˚
1000 Hz
300 Hz
6000 Hz

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 foam-
block wire. A snug fit of the foam pad pre-
vents boom bounce when you move around.
5. Be sure that the thumbscrew is still loos-
ened 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 adjust-
ments 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,
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
batterycover.
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:
* 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:
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, noise-
cancelling,
cardioi
Th
e
axi
s
Th
e
headband
thumbscre
Mode
pack
permanentl
shielde
phon
includ
necto
Mode
batte
phanto
batte
on/off
Nomina
or
1.2
148
shall
response
a
uniform
dow
model
Mic
AKG/C
gua
malfunction
thre
Se
e
info
Se
r
If
th
erl
y
connecte
you
defective, return the complete product in its
original packaging to one of the addresses
below
supportcall
[phone].
cardioi
d type of electret-condenser design.
e
microphone shall exhibit excellent off-
s
response and gain-before-feedback.
e
microphone shall have an adjustable
headband
, adjustable boom with locking
thumbscre
w, and foam pop filter.
Mode
l CM311 A shall include a battery belt
pack
. In the CM311 A, a 42-inch,
permanentl
y attached, two-conductor
shielde
d cable shall connect the micro-
phon
e to the belt pack. The belt pack shall
includ
e a 3-pin pro audio (XLR type) con-
necto
r.
Mode
l CM311 A shall be powered by a 9 V
batte
ry in the belt pack, or by 18 to 48 V
phanto
m power. The belt pack shall have a
batte
ry on/off switch, a programmable mic
on/off
switch, and a “Mic On” LED.
Nomina
l open-circuit sensitivity shall be 4
1.2
5 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
uniform
off-axis response, over 20 dB
dow
n at the rear null. The AKG/Crown
model
CM311 A isspecified.
Mic
rophone Warranty
AKG/C
rown professional microphones are
gua
ranteed unconditionally against
malfunction
from any cause for a period of
thre
e years from date of original purchase.
e
enclosed warranty sheet for additional
info
rmation.
r
vice
th
e microphone does not function prop-
y
, check that it is aimed correctly and is
connecte
d as described in this data sheet. If
you
determine that the microphone product is
defective, return the complete product in its
original packaging to one of the addresses
below
. For further assistance or technical
supportcall
the international helpdesk at
[phone].

AKG
ACOUSTICS GMBH
AKG ACOUSTICS, U.S.
© 2015 HARMAN International Industries, Incorporated. All rights reserved.
United States and/or other countries.
Features, specifications and appearance are subject to change without notice.
www.akg.com
CM
CM
CM311 L
1
CM311 A Schematic
ACOUSTICS GMBH
LAXENBURGER STRASSE 254, 1230 VIENNA/AUS
TRIA
AKG ACOUSTICS, U.S.
SERVICE 24950 GROVE VIEW ROA
D, MORENO VALLEY, CA
© 2015 HARMAN International Industries, Incorporated. All rights reserved.
AKG is a trademark of
AKG
Features, specifications and appearance are subject to change without notice.
CM
311 A
CM
311 AESH
CM311 L
TRIA
D, MORENO VALLEY, CA
92551, U.S.A
AKG
Acoustics GmbH, registered in the