Shure SM81-LC Condenser Cardioid Instrument Microphone
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Cardioid condenser instrument microphone offers a wide frequency response and low self-noise. Features include flat response curve, low noise and high output clipping level, low distortion over a range of load impedances, and low RF susceptibility.
The SM81 is the perfect choice for a professional musician or sound engineer who is looking to mic up acoustic instruments such as acoustic guitar, piano and cymbals. It can ideally be used on stage and because of its high quality is also at home in the recording studio.
What characteristics can I expect when using an SM81?
The SM81 has a flat response curve for accurate reproduction of the sound source and can also be modified via a bass roll off switch. The 0dB/10bB lockable attenuator switch gives you even more flexibility when miking up loud sound sources and it has a cardioid polar pattern which isolates the main sound source while minimizing handling noise.
- 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
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.
Features
- Uniform cardioid pick-up pattern for maximum gain before feedback and excellent rejection of off-axis sound
- Flat frequency response for accurate reproduction of sound sources; 20 Hz to 20 kHz
- Selectable low frequency response; flat, 6 or 18 dB/octave roll off
- Vinyl-coated steel construction and stainless steel screen resist wear and abuse
- Low noise and high sound pressure level (SPL) handling
- Minimally affected by varying load impedances
- Low susceptibility to RFI
- Lockable 10 dB attenuator switch
- Performs over a wide range of temperature and humidity conditions
- Phantom powered
- Shure quality, ruggedness, and reliability
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 or XLR-to-TRS.
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., close-miked 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 (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 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 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 -3 dB
Polarity - Positive pressure on 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 difference between 94 dB SPL and equivalent SPL of self noise, A-weighted
Block Diagram
Typical Frequency Response
Typical Polar Patterns
Overall Dimensions
Connector | XLR |
Highest frequency | 20000 Hz |
Impedance | 150 ohm |
Lowest Frequency | 20 Hz |
Max. SPL | 136 dB |
Polar Pattern | Cardioid |
Type capsule | Condenser |
Type microphone | Instrumental |
Warranty | 24 months |
AT8471 isolation clamp for 5/8"-27 threaded stands; 5/8"-27 to 3/8"-16 threaded adapter; AT8136 windscreen; soft protective pouch
Package weight: 0.90 kg