Crown DIFFEROID CM-311A Operating instructions

©2000 Crown International, Inc.
Specifications subject to change without prior notice.
Crown® and Differoid®are registered trademarks of
Crown International, Inc.
02/00 102546-4
CM-311AE Schematic
CM-311A
CM-311AE
Crown International, Inc.
P. O. Box 1000
Elkhart, IN 46515-1000
TEL: [phone]
FAX: [phone]FAX
CM-311A Schematic
1

CM-311A
CM-311AE
DIFFEROID®HEAD-WORN
CONDENSER MICROPHONE
Designed 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 the
wireless transmitter of your choice.
How to adjust for best fit and to prevent
boom bounce
Note: To get maximum the 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 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.
Specifications
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 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.
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 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-inch (13.97 cm)
diameter, adjustable. Boom approximately 7-
inch (17.78 cm) x 3-inch (7.62 cm). See
Figs. 3 and 4.
Included accessories: Microphone carrying
case, WS-6 foam pop filter, clothing clip.
Optional accessories: PH-4B phantom power
supply (4 channels, AC powered). PH-1A
phantom power supply (1 channel, battery
or AC-adapter powered). WS-14 accessory
windscreen.
*1 pascal = 10 dynes/cm2= 10 microbars = 94 dB SPL.

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

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 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 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.
Fig. 5
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:
How to connect the CM-311AE to a wire-
less transmitter
1. Solder on a connector that mates with
your transmitter. Technical Bulletin #3 (in-
cluded) 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.
Architects’ and Engineers’ Specifications
The microphone shall be the Crown Model
CM-311A 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 microphone alone. In the CM-311A, a
42-inch, permanently attached, two-conduc-
tor shielded cable shall connect the micro-
phone to the belt pack. The belt pack shall
include a 3-pin pro audio (XLR type) con-
nector. In the CM-311AE, a 42-inch, perma-
nently attached, two-conductor shielded
cable can be connected to a transmitter.
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 specified.
Microphone Warranty
Crown professional microphones are guar-
anteed unconditionally against malfunction
from any cause for a period of three years
from date of original purchase. See en-
closed warranty sheet for additional infor-
mation.
Service
If the microphone does not function prop-
erly, check that it is aimed correctly and is
connected as described in this data sheet. If
the microphone is defective, return it in the
original packaging to: Crown Service De-
partment, Plant 2SW, 1718 West
Mishawaka Road, Elkhart, IN 46517. For
further assistance or technical support call
800-342-6939.
The LED lights when the mic is on.