The Shure SM81 is a high-quality, unidirectional condensermicrophone designed for studio recording, broadcasting, and soundreinforcement. Its wide frequency response, low noise characteristics, and lowRF susceptibility have made it a standard for applications involving acousticinstruments, especially guitar, piano, and cymbals. POWER REQUIREMENTS NOTE:This microphone requires phantom power and performs best with a 48 Vdc supply(IEC-61938). However, it will operate with slightly decreased headroom andsensitivity with supplies as low as 11 Vdc. Most modern mixers provide phantompower. You must use a balanced microphone cable: XLR-to-XLR or XLR-to-TRS. Built to withstand the rigors of regular stage and studio use, theShure SM81 unidirectional condenser microphone is a great choice for studiorecording, broadcasting, and sound reinforcement. Its wide frequency response,low noise characteristics, and low RF susceptibility make it a perfect matchfor applications involving acoustic instruments, especially guitar, piano, andcymbals. Ruggedly constructed, the SM81 operates on phantom power and performsover a wide range of temperatures and humidity conditions. It comes with aswivel adapter, attenuator-switch lock, foam windscreen, and case for carryingand storage. Key Features Frequency response. Polar pattern.Flat responsecurve for accurate reproduction of sound sources Low noise and high outputclipping level Low distortion over a wide range of load impedances Cardioidpolar pattern, uniform with frequency and symmetric about axis, providingmaximum rejection and minimum coloration of off-axis sounds Low RFsusceptibility Selectable low-frequency response: flat, 6 or 18 dB/octaverolloff 0 dB/10 dB lockable attenuator switch Phantom powering (DIN 45 596voltages of 12 to 48 Vdc) Rugged steel construction for durability Field-usable over wide range of temperature and humidity conditionsSpecificationsType: Condenser (electret bias) Frequency Response: 20 to 20,000Hz Polar Pattern: Cardioid (unidirectional) response-uniform with frequency,symmetrical about axis Output Impedance: Rated at 150 ohms (85 ohms actual)Recommended minimum load impedance: 800 ohms (May be used with loads as low as150 ohms with reduced clipping level) Output Configuration and Connector:Balanced, transformer-coupled output; male XLR connector Sensitivity (at 1,000Hz): Open Circuit Voltage: -45 dBV/Pascal (5.6 mV); (1 Pascal = 94 dB SPL)Clipping Level (at 1,000 Hz): 800 ohm Load: -4 dBV (0.63 V); 150 ohm Load: -15dBV (0.18 V) Total Harmonic Distortion Less than 0.5% (131 dB SPL at 250 H: zinto 800 ohm load) Maximum SPL (at 1,000 Hz): 800 ohm load: 136 dB (attenuatorat 0) 146 dB (attenuator at -10) 150 ohm load: 128 dB (attenuator at 0) 138 dB(attenuator at -10) Hum Pickup: -3 dB equivalent SPL in a 1 mOe field (60 Hz)Self-Noise (equivalent sound pressure levels; measured with true rmsvoltmeter): 16 dB typical, A-weighted; 19 dB typical, weighted per DIN 45 405Signal-to-Noise Ratio: 78 dB (IEC 651) at 94 dB SPL S/N ratio is differencebetween 94 dB SPL and product's equivalent self noise (SPL A-weighted).Overvoltage and Reverse Polarity Protection: Max. external voltage applied topins 2 and 3 with respect to pin 1: +52 Vdc Reverse polarity protection: 200mA max. (diode-clamped) Polarity: Positive pressure on diaphragm producespositive voltage on pin 2 relative to pin 3 Cartridge Capacitance: 54 pF LowFrequency Response Switch Positions: Flat; -6 dB/octave below 100 Hz; -18dB/octave below 80 Hz Attenuator Switch Positions (Lockable): 0 or -10 dBPower: Supply Voltage: 11 to 52 Vdc, positive, pins 2 and 3 Current Drain: 1.2mA max. Case: Steel construction with vinyl metallic paint finish andstainless steel screens Weight: 8 ouncesThis 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.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.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.