The Neumann U 87 Ai nickel-plated condenser microphone is a large dual-diaphragm microphone. It offers three directivities, including omnidirectional, cardioid and figure-8. These are selectable using a switch located beneath the head grille, and the window above this switch displays the symbol of the selected characteristic. A 10 dB attenuation switch is located at the rear. It allows the microphone to handle sound pressure levels up to 127 dB without distortion. The low-frequency response can be reduced to compensate for proximity effect. The U 87 Ai is used as a main microphone for orchestral recordings, as a spot microphone for solo instruments, and widely as a vocal microphone for all types of music and speech. The U 87 Ai is addressed from the front. The frequency response of the cardioid and figure-8 directional characteristics is very flat for frontal sound incidence, even in the high frequencies. The microphone can be used very close to a sound source without the sound becoming abnormally harsh. Thanks to a high-pass filter, interference from subsonic and low frequencies is reduced. The circuit increases the operating margin of the U 87 Ai by providing the bias voltages for the capsule through a reduced resistance. The result is 10 dB higher sensitivity for identical sound pressure levels, and an improved signal-to-noise ratio of 3 dB. A switch at the rear attenuates the sensitivity by 10 dB. When this switch is activated, the microphone accepts sound pressure levels up to 127 dB (equivalent to an acoustic pressure of 45 Pa) without distortion. An additional switch at the rear allows modification of the microphone's cut-off frequency. This reduces low-frequency interference directly at the microphone amplifier input. This setting also compensates for the inevitable bass emphasis that occurs with all pressure gradient transducers when used at short distances (proximity effect). The cardioid characteristic maintains a regular frequency response at a distance of 30 to 40 cm, and the figure-8 characteristic at a distance of 15 to 20 cm. - Variable large-diaphragm microphone - Pressure gradient transducer with dual-diaphragm capsule - Omnidirectional, cardioid and figure-8 characteristics - Switchable low-frequency attenuation - Switchable 10 dB pre-attenuation - Excellent as main or spot microphone