The Neumann U 87 Ai nickel electrostatic microphone is a large-diaphragm, dual-membrane condenser microphone. It features three polar patterns, including omnidirectional, cardioid and figure-8. These are selectable using a switch located beneath the 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 of up to 127 dB without distortion. The low-frequency response can be reduced to compensate for the proximity effect.

The U 87 Ai is used as a main microphone for orchestral recordings, as a spot microphone for individual instruments, and widely as a vocal microphone for all types of music and speech.

The U 87 Ai is front-addressed. The frequency response of the cardioid and figure-8 directional characteristics is very flat for frontal sound incidence, even at high frequencies. The microphone can be used very close to a sound source without the sound becoming artificially harsh. By means of a high-pass filter, interference from subsonic and low frequencies is reduced.

The circuit increases the headroom of the U 87 Ai by supplying the polarisation voltages for the capsule through a reduced resistance. The result is a sensitivity 10 dB higher 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 of up to 127 dB (equivalent to a sound pressure of 45 Pa) without distortion.

An additional switch at the rear allows the cut-off frequency of the microphone to be modified. This reduces low-frequency interference directly at the input of the microphone amplifier. This setting also compensates for the inevitable bass emphasis that occurs with all pressure-gradient transducers when used at close range (proximity effect).

The cardioid characteristic maintains a smooth 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-membrane capsule

- Omnidirectional, cardioid and figure-8 characteristics

- Switchable low-frequency attenuation

- Switchable 10 dB pre-attenuation

- Excellent as a main microphone or spot microphone