SHURE SM81 Instrument Microphone User Guide

SHURE SM81 Instrument Microphone General Description

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. 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.

Power Requirements

This microphone requires phantom power and performs best with a 48 Vdc supply (IEC-61938). However, it will operate with slightly decreased headroom and sensitivity with supplies as low as 11 Vdc.
Most modern mixers provide phantom power. You must use a balanced microphone cable: XLR-to-XLR.

Selecting Low-Frequency Response

A three-position switch allows you to adjust the low-frequency response of the microphone. Use these settings to reduce wind noise, room noise or proximity effect.

Flat response provides the most natural sound in most applications.
Low-frequency cutoff attenuates 18 dB-per-octave below 80 Hz. Helps eliminate floor rumble and low-frequency room noise from heating and air conditioning systems. This setting may also be used to compensate for proximity effect or to reduce low frequencies that make an instrument sound dull or muddy.
Low-frequency rolloff attenuates 6 dB-per-octave below 100 Hz. Compensates for proximity effect or to reduce low frequencies that could make an instrument sound dull or muddy.

Setting Attenuation

The attenuation switch reduces the signal level from the cartridge by 10 dB without altering the frequency response. This can prevent extremely high SPLs (e.g., close­miked drums and guitar cabinets) from overloading the microphone. To activate atten­uation, rotate the switch to the “–10 dB” position.
NOTE: Turning the ring part way does not produce incremental levels of attenuation.
The attenuation switch may be locked in place. Use the following steps:

1. Unscrew the grille and cartridge assembly.
2. Rotate the attenuation switch to the desired position (0 or –10).
3. Insert the ring lock (a small, clear piece of plastic) in the area behind the ring between the pin and slot.
4. Replace the grille and cartridge assembly.

Proximity Effect

Unidirectional (cardioid) microphones progressively boost bass frequencies by 6 to 10 dB below 100 Hz when the microphone is at a distance of about 6 mm (1/4 in.) from the sound source. This phenomenon, known as the proximity effect, can be used to create a warmer, more powerful sound. To prevent explosive low-frequency sound during close-up use, the bass response gradually rolls off. This provides greater control and helps the user take advantage of the proximity effect.

Specifications

• Type
  Electret Condenser
  Frequency Response
  20 to 20,000 Hz

• Polar Pattern
  Cardioid

• Output Impedance
  EIA rated at 150 Ω (85 Ω actual)

• Sensitivity
  at 1 kHz, open circuit voltage
  ­45 dBV/Pa[1] (5.6 mV)

• Maximum SPL
  1 kHz at 1% THD, 1 kΩ load
  136 dB SPL

• Signal-To-Noise Ratio
  Ref. 94 dB SPL at 1 kHz
  78 dB[2]

• Clipping Level
  1 kHz at 0.25% THD, 1 kΩ load
  ­4 dBV (0.63 V)

• Hum Pickup
  typical, at 60 Hz, equivalent SPL/mOe

• Polarity
  Positive pressure on the diaphragm produces positive voltage on pin 2 with respect to pin 3

• Weight

  • Net
  • 0.230 kg (0.5 lbs)
  • Packaged
  • 0.740 kg (1.625 lbs)

• Attenuator Switch
  0 or −10 dB, lockable

• Connector
  Three-pin professional audio (XLR), male

• Housing
  Steel construction with vinyl metallic paint finish and stainless steel screens

Environmental Conditions

• Operating Temperature
  • -6.7° to 49° C (20° to 120° F)
• Storage Temperature
  • -29° to 74° C (-20° to 165° F)
• Relative Humidity
  • 0 to 95%

Power Requirements

11 to 52 V DC phantom power (1.2 mA)

1. 1 Pa=94 dB SPL
2. S/N ratio is the difference between 94 dB SPL and equivalent SPL of self-noise, A-weighted

Accessories

Furnished Accessories

Optional Accessories

Replacement Parts

Certifications

This product meets the Essential Requirements of all relevant European directives and is eligible for CE marking.
The CE Declaration of Conformity can be obtained from: www.shure.com/europe/compliance
Authorized European representative:

• Shure Europe GmbH
• Global Compliance
• Jakob-Dieffenbacher-Str. 12
• 75031 Eppingen, Germany
• Phone: +49-7262-92 49 0
• Email: info@shure.de
• www.shure.com

References

• Shure: Microphones, Wireless microphones, in-ear monitoring, earphones, headphones - Shure USA

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