MODEL SM81
UNIDIRECTIONAL CONDENSER MICROPHONE
The Shure Model SM81 is a high-quality, unidirectional
condenser microphone designed for studio recording, broad-
casting, and sound reinforcement. Its wide frequency re-
sponse, low noise characteristics, and low RF susceptibility
have made it a standard for applications involving acoustic in-
struments, especially guitar, piano, and cymbals.
The SM81 is ruggedly constructed. It operates on phantom
power and performs over a wide range of temperatures and hu-
midity conditions. It is furnished with a swivel adapter, attenua-
tor-switch lock, foam windscreen, and case for carrying and
storage. Other accessories are available.
Model SM81 Features
•20 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 symme-
tric 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
SPECIFICATIONS
Type
Condenser (electret bias)
Frequency Response
20 to 20,000 Hz (see Figure 1)
20 200001000 10000
50 100
98765432 98765432
+10
0
–10
Hz
dB
1 METER
TYPICAL FREQUENCY RESPONSE
FIGURE 1
Polar Pattern
Cardioid (unidirectional) response—uniform with
frequency, symmetrical about axis (see Figure 2)
150o
120o
150o
120o
180o
30o
60o
90o
30o
60o
90o
–5 dB
–10 dB
–15 dB
–20 dB
0
500 kHz
100 Hz
1 kHz
150o
120o
150o
120o
180
o
30o
60 o
90o
30 o
60o
90o
–5 dB
–10 dB
–15 dB
–20 dB
0
2 kHz
5 kHz
10 kHz
TYPICAL POLAR PATTERNS
FIGURE 2
Output Impedance
Rated at 150 Ω (85 Ω actual)
Recommended minimum load impedance: 800 Ω (May
be used with loads as low as 150 Ω with reduced clip-
ping level)
Output Configuration and Connector
Balanced, transformer-coupled output; male XLR con-
nector
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)
Model SM81 User Guide
27B2916 (BJ)
E2002, Shure Incorporated Printed in U.S.A.
