Shure SM81-LC User Manual
MODEL SM81
UNIDIRECTIONAL CONDENSER MICROPHONE
OVERVIEW
The Shure Model SM81 is a high-quality, unidirectional condenser microphone designed for studio recording, broadcasting,
and sound reinforcement. Its wide frequency response, low
noise characteristics, and low RF susceptibility have made it a
standard for applications involving acoustic instruments, especially guitar, piano, and cymbals.
FEATURES
S 20 Hz to 20 kHz frequency response
S Flat response curve for accurate reproduction of sound
sources
S Low noise and high output clipping level
S Low distortion over a wide range of load impedances
S Cardioid polar pattern, uniform with frequency and symme-
tric about axis, providing maximum rejection and minimum
coloration of off-axis sounds
Model Model SM81 Microphone
Specification Sheet
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.
S Low RF susceptibility
S Selectable low-frequency response: flat, 6 or 18 dB/octave
rolloff
S 0 dB/10 dB lockable attenuator switch
S Phantom powering (DIN 45 596 voltages of 12 to 48 Vdc)
S Rugged steel construction for durability
S Field-usable over wide range of temperature and humidity
conditions
SPECIFICATIONS
Type
Condenser (electret bias)
Frequency Response
20 to 20,000 Hz
+10
0
dB
–10
20 200001000
50 100
TYPICAL FREQUENCY RESPONSE
Hz
1 METER
98765432
98765432
10000
Polar Pattern
Cardioid (unidirectional) response—uniform with frequen-
cy, symmetrical about axis (see Figure NO TAG)
o
180
o
150
o
120
o
90
o
60
–20 dB
–15 dB
–10 dB
–5 dB
o
30
0
1 kHz
500 kHz
100 Hz
150
o
o
120
o
90
o
60
o
30
150
o
120
o
90
o
60
30
o
o
2 kHz
5 kHz
10 kHz
180
–20 dB
–15 dB
–10 dB
–5 dB
o
150
0
TYPICAL POLAR PATTERNS
o
o
120
o
90
o
60
o
30
MODEL SM81 CONDENSER MICROPHONE
Specification Sheet
Output Impedance
Rated at 150 ohms (85 Ω actual)
Recommended minimum load impedance: 800 Ω (May be
used with loads as low as 150 Ω 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 Ω Load –4 dBV (0.63 V). . . . . . . . . . . . . . . . . . . . . . .
150 Ω Load –15 dBV (0.18 V). . . . . . . . . . . . . . . . . . . . . .
Total Harmonic Distortion
Less than 0.5% (131 dB SPL at 250 Hz into 800 Ω load)
Maximum SPL (at 1,000 Hz)
800 Ω load 136 dB (attenuator at 0). . . . . . . . . . . . . . . .
146 dB (attenuator at –10)
150 Ω 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 microphone output at 94 dB SPL
and microphone self-noise 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_ to 74_ C. . . . . . . . . . . . . . . . . . . . . . .
(–20_ to 165_ F)
Operating – 6.7_ to 49_ C. . . . . . . . . . . . . . . . . . . . . .
(20_ to 120_ F)
Humidity:
Storage 0–95% relative humidity at room. . . . . . . .
temperature (72_to 80_ F, 22_ to 27_ C)
Case
Steel construction with vinyl metallic paint finish and stain-
less steel screens
Dimensions
See Figure NO TAG
Weight
Net 230 grams (8 oz). . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Packaged 740 grams (1 lb 10 oz). . . . . . . . . . . . . . . . . .
FURNISHED ACCESSORIES
Swivel Adapter A57F. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 dB Attenuator Lock 34A830. . . . . . . . . . . . . . . . . . . . . . . . .
REPLACEMENT PARTS
Cartridge and Grille Assembly R104. . . . . . . . . . . . . . . . . . .
OPTIONAL ACCESSORIES
Pop-Filter Grille A81G. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heavy-Duty Windscreen A81WS. . . . . . . . . . . . . . . . . . . . . . .
Tripod Microphone Stand (4.3 m [14 ft]) S15A. . . . . . . . . . . .
Carrying/Storage Case 65A1797. . . . . . . . . . . . . . . . . . . . . . .
Windscreen 49A111. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stereo Microphone Adapter A27M. . . . . . . . . . . . . . . . . . . . . .
Cable (7.6m [25ft]) C25F. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Phantom Power Supply PS1A. . . . . . . . . . . . . . . . . . . . . . . . .
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