Shure SM81-LC Cardioid Condenser Instrument Microphone

• Flat response from 20 Hz to 20 kHz, for faithful reproduction of the source
• Three-position low-cut: flat, 6 dB per octave below 100 Hz or 18 dB per octave below 80 Hz
• Lockable 10 dB attenuator that leaves the frequency response unchanged
• Cardioid pattern that stays consistent with frequency and symmetrical about the axis
• Steel construction, usable across a wide range of temperature and humidity

The three-position switch acts on the bottom of the spectrum only. The flat setting gives the most natural sound in most cases. The 18 dB per octave cutoff below 80 Hz removes floor rumble and background noise from heating or air conditioning. The 6 dB per octave rolloff below 100 Hz offsets the proximity effect, or lightens an instrument whose low end sounds dull and muddy.

A ring cuts the capsule's signal by 10 dB without touching the frequency response: that is what prevents overload in front of a close-miked drum kit or guitar cabinet. The ring has only two positions, 0 and -10 dB; turning it part way gives no in-between value.

The setting can be locked. Unscrew the grille and cartridge assembly, choose the position, insert the small clear plastic piece supplied behind the ring, then screw everything back on.

The SM81 runs on phantom power, ideally 48 V, and accepts voltages as low as 11 V with slightly less headroom. It connects with a balanced XLR-to-XLR cable. Its rated impedance is 150 ohms, for 85 ohms actual. Shure rates it for use from -6.7 to 49 °C and up to 95% relative humidity: a mic that can leave the studio.

• Acoustic guitar, in the studio and on stage
• Piano, close-miked
• Cymbals and hi-hat above the drum kit
• Stereo pair on a single stand, with the optional A27M stereo adapter

Other cardioid condenser instrument microphones, from other manufacturers. Data as published by each manufacturer.

Does the SM81 need phantom power?

Yes: 11 to 52 V DC, drawing 1.2 mA. Shure says it gives its best results at 48 V and that at lower voltages, headroom and sensitivity drop slightly.

Is the SM81 a condenser microphone?

Yes, an electret condenser with a cardioid pattern. It is not a dynamic mic: it needs phantom power to work.

What is the SM81 good for?

Shure designs it for studio recording, broadcasting and sound reinforcement, and presents it as a standard for acoustic instruments, especially guitar, piano and cymbals.

Can two SM81s be set up as a stereo pair?

Yes. Shure offers the optional A27M stereo adapter, which holds two mics on a single stand, for example for a pair above the drum kit. The supplied A57F clip fits standard mic stands.