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CardioidShure SM81

Cardioid Pencil Condenser Microphone

The Shure SM81 is a cardioid condenser microphone characterized by wide frequency response, low noise characteristics, and low RF susceptibility.

It is furnished with a swivel adapter, attenuator-switch lock, foam windscreen, and case for carrying and storage. Other accessories are available.

  • 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 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

The body diameter is 20mm.


If you have an ear for recordings, you will recognize the sound of the SM81. It’s been on tons of records. When I hit the first strum on this old classical guitar, I immediately shouted “Yes!” The strings are clearly articulated, and the bass regions come through with definition…

One of first experiments was to try stereo miking with an SM81 close in and a Neumann TLM 103 back about a foot. I really liked that sound a lot as it gave good depth… Then I tried the typical X-Y approach with my Octava MK012 at 90 degrees. The result was good, but not as rich as the previous experiment. When I soloed the Octava then soloed the SM81 I could figure out why. The Octava was much more a mid-rangy sound, not as deep, lush, or articulate as the SM81.

See the sidebar link to mic expert Scott Dorsey’s SM81 mod, which involves removing the windscreen that sits in front of the mic’s capsule. The result is a more open sound, with a more accurate HF response, at a cost of some loss of protection for the diaphragm (as is always the case with open-headbasket mods). This article was originally published in Recording Magazine.

The Shure SM81 is also known as: SM-81.

The mic was released in 1978.


Frequency Response - CardioidClick Graph to Compare!
SM81 Cardioid Frequency Response Chart
Pickup Patterns Pads & Filters
Cardioid (5.6 mV/Pa; 20 - 20,000 Hz)
  • Pad: -10dB (Via Switch)
  • Filter: HPF: -6dB/octave (Via Switch)
  • Filter: HPF: -18dB/octave (Via Switch)
Capsule Dimensions Impedance SPL/Noise
Diameter n/a
85 Ohms (Low) Max SPL: 146 dB
Self-noise: 16.0 dB(A)
Weight Length Max Diameter Interface(s)
230g (8.11oz) 212mm (8.35'') 24mm (0.94'')
  • 3-pin XLR male (1)
Power Specifications
  • Requires phantom power
  • Phantom voltage: 11-52v

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