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POLAR
PATTERN
CM-31
CM-31W
MINIATURE CONDENSER
HANGING MICROPHONE
T
he Crown
®
CM-31 is a professional-
quality, supercardioid condenser micro-
phone designed for inconspicuous miking
of a choir, orchestra or stage. It can also hang
over conference tables or discussion groups for
inconspicuous isolated miking.
The CM-31 consists of two parts: the micro-
phone with a permanently attached 30-foot
(9.15-m) cable and the cylindrical electronics
power module.
The mic cable connects to the power module,
which adapts the microphone for phantom
powering and includes a low-cut switch. Cable
connection is via miniature 3-pin connectors.
The power module output is balanced, low
impedance. It is protected against static and
radio-frequency interference.
The CM-31 has a smooth, wide-range frequency
response for natural reproduction of the singing
voice, organ or other musical instruments. Ex-
treme low frequencies are fi ltered out to reduce
pickup of room rumble.
The microphone has a built-in removable
hanger which allows easy position adjustment.
The CM-31 microphone and cable are black; the
CM-31W microphone and cable are white.
Operating Instructions
The power module supplied has been matched
to the microphone. For best performance do not
intermix microphones and modules.
Plug the microphone into the electronics power
module. Run a 2-conductor shielded mic cable
(not supplied) from your mixer to the power
module, and plug it in.
Experiment with microphone placement before
permanently installing the power module. A
suggested placement for choir sound reinforce-
ment is shown in Figs. 4a and 4b. For recording
or broadcast, you might want to place the
microphone a few feet farther away to pick up
more room acoustics. Bend the wire hanger to
achieve the desired pickup angle.
If rumble from trucks or air-conditioning is
excessive, switch in the low-cut fi lter on the
power module. The low-cut position (
) is
toward the microphone.
After fi nding the desired microphone position,
install the power module in one of three ways:
• Install the power module in the ceiling (Fig.
6). Pull up the mic cable until the mic is at the
desired height, then knot the cable.
• Clamp the power module to a beam overhead
(Fig. 7).
• Tape the power module to the fl oor.
Specifi cations
Type: Unidirectional condenser.
Transducer: Electret condenser.
Frequency Response (typical): 40 Hz to 20,000 Hz
(see Fig. 1).
Polar Pattern: Supercardioid (see Fig. 2).
Impedance: 150 ohms, balanced. Recommended
minimum load impedance 1000 ohms.
Open Circuit Sensitivity: 10 mV/Pa* (–40 dB re 1
volt/Pa).
Power Sensitivity: –37.5 dB re 1 mW/Pa.
Equivalent Noise Level: 28 dB SPL typical (0 dB =
.0002 dyne/cm
2
), A-weighted.
S/N Ratio: 66 dB at 94 dB SPL.
Maximum Sound Pressure Level: 120 dB SPL
produces 3% THD.
Mic-Cable Connector: TA3F (mini XLR-type).
Power Module Connector (input): TB3M (mini XLR-
type). See Fig. 3.
Power Module Connector (output): 3-pin male XLR-
type.
Power Module Switch: Flat/low-cut.
Operating Voltage: Phantom power, 12 to 48 volts
DC, positive voltage on pins 2 and 3 with respect to
pin 1 of output connector.
Materials: Brass housing, steel power module hous-
ing.
Finish: Black (CM-31) or white (CM-31W).
Weight (microphone and cable): 4 ounces (113
grams).
Weight (microphone, cable and power module): 9.5
ounces (269 grams).
Cable: Black (CM-31) or white (CM-31W), 30' (9.15-
m) 2-conductor shielded 0.1" (.254-cm) diameter
cable from microphone to electronics; none
supplied for electronics output. Use 2-conductor
shielded microphone cable.
Dimensions: See Fig. 5 on reverse side.
Included Accessories: WS5 black foam windscreen
for CM-31, WS5W white foam windscreen for
CM-31W.
Optional Accessories: Crown PH-1A phantom power
supply (1 channel, battery or AC adaptor powered).
*1 pascal = 10 dynes/cm
2
= 10 microbars = 94 dB SPL.
Fig. 1
Frequency in Hz
Frequency Response
Fig. 2
Polar Response
Fig. 3
Features
• Ideal for picking up choirs
• Supercardioid polar pattern aids gain-before-
feedback and rejects background noise
• Small and inconspicuous
• Hanger allows position adjustment
• XLR connector with built-in electronics