POLAR
PATTERN
MINIATURE CONDENSER
HANGING MICROPHONE
CM-31
CM-31W
he Crown® CM-31 is a professional-
quality, supercardioid condenser micro-
phone designed for inconspicuous miking
T
of a choir, orchestra or stage. It can also hang
over conference tables or discussion groups for
inconspicuous isolated miking.
Features
• Small and inconspicuous
• Hanger allows position adjustment
• XLR connector with built-in electronics
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.
• Ideal for picking up choirs
• Supercardioid polar pattern aids gain-before-
feedback and rejects background noise
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.
Specifications
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).
Fig. 1
Frequency Response
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 filtered 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.
Power Sensitivity: –37.5 dB re 1 mW/Pa.
Equivalent Noise Level: 28 dB SPL typical (0 dB =
.0002 dyne/cm2), A-weighted.
Frequency in Hz
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.
Operating Instructions
The power module supplied has been matched
to the microphone. For best performance do not
intermix microphones and modules.
Fig. 2
Polar Response
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 filter on the
power module. The low-cut position (
toward the microphone.
) is
After finding the desired microphone position,
install the power module in one of three ways:
Fig. 3
Dimensions: See Fig. 5 on reverse side.
• 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.
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).
• Clamp the power module to a beam overhead
(Fig. 7).
• Tape the power module to the floor.
*1 pascal = 10 dynes/cm2 = 10 microbars = 94 dB SPL.
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