Shure SM81 Cardioid Condenser Mic

The SM81 is ruggedly constructed. It operates on phantom power and performs over a wide range of temperatures and humidity conditions. It is furnished with a swivel adapter, attenuator-switch lock, foam windscreen, and case for carrying and storage. Other accessories are available.

• 0 Hz to 20 kHz frequency response
• Flat response curve for accurate reproduction of sound sources
• Low noise and high output clipping level
• Low distortion over a wide range of load impedances
• Cardioid polar pattern, uniform with frequency and symmetric about axis, providing maximum rejection and minimum coloration of off-axis sounds
• Low RF susceptibility
• Selectable low-frequency response: flat, 6 or 18 dB/octave rolloff
• 0 dB/10 dB lockable attenuator switch
• Phantom powering (DIN 45 596 voltages of 12 to 48 Vdc)
• Rugged steel construction for durability
• Field-usable over wide range of temperature and humidity conditions

Type
Condenser (electret bias)

Frequency Response
20 to 20,000 Hz

Polar Pattern
Cardioid (unidirectional) response-uniform with frequency, symmetrical about axis

Output Impedance
Rated at 150 ohms (85 ohms actual)
Recommended minimum load impedance: 800 ohms (May be used with loads as low as 150 ohms with reduced clipping level)

Output Configuration and Connector
Balanced, transformer-coupled output; male XLR connector

Sensitivity (at 1,000 Hz)
Open Circuit Voltage: -45 dBV/Pascal (5.6 mV
(1 Pascal = 94 dB SPL)

Clipping Level (at 1,000 Hz)
800 ohm Load: -4 dBV (0.63 V)
150 ohm Load: -15 dBV (0.18 V)

Total Harmonic Distortion
Less than 0.5% (131 dB SPL at 250 Hz into 800 ohm load)

Maximum SPL (at 1,000 Hz)
800 ohm load: 136 dB (attenuator at 0) 146 dB (attenuator at -10)
150 ohm load: 128 dB (attenuator at 0) 138 dB (attenuator at -10)

Hum Pickup
-3 dB equivalent SPL in a 1 mOe field (60 Hz)

Self-Noise (equivalent sound pressure levels; measured with true rms voltmeter)
16 dB typical, A-weighted
19 dB typical, weighted per DIN 45 405

Signal-to-Noise Ratio
78 dB (IEC 651)* at 94 dB SPL
*S/N ratio is difference between 94 dB SPL and product's equivalent self noise (SPL A-weighted).

Overvoltage and Reverse Polarity Protection
Max. external voltage applied to pins 2 and 3 with respect to pin 1: +52 Vdc
Reverse polarity protection: 200 mA max. (diode-clamped)

Polarity
Positive pressure on diaphragm produces positive voltage on pin 2 relative to pin 3

Cartridge Capacitance
54 pF

Low Frequency Response Switch Positions
Flat; -6 dB/octave below 100 Hz; -18 dB/octave below 80 Hz

Attenuator Switch Positions (Lockable)
0 or -10 dB

Power
Supply Voltage: 11 to 52 Vdc, positive, pins 2 and 3
Current Drain: 1.2 mA max.

Environmental Conditions
Temperature:
Storage: -29 degrees to 74 degrees C (-20 degrees to 165 degrees F)
Operating: -6.7 degrees to 49 degrees C (20 degrees to 120 degrees F)

Humidity:
Storage 0 to 95% relative humidity at room temperature (72 degrees to 80 degrees F, 22 degrees to 27 degrees C)

Case
Steel construction with vinyl metallic paint finish and stainless steel screens

Dimensions
See User Guide

Weight
Net: 230 grams (8 oz)
Packaged: 740 grams (1 lb 10 oz)