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 responseFlat response curve for accurate reproduction of sound sourcesLow noise and high output clipping levelLow distortion over a wide range of load impedancesCardioid polar pattern, uniform with frequency and symmetric about axis, providing maximum rejection and minimum coloration of off-axis soundsLow RF susceptibilitySelectable low-frequency response: flat, 6 or 18 dB/octave rolloff0 dB/10 dB lockable attenuator switchPhantom powering (DIN 45 596 voltages of 12 to 48 Vdc)Rugged steel construction for durabilityField-usable over wide range of temperature and humidity conditionsThe Shure 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.