Crown Audio Microphone CM 31 User Manual

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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