Neumann - U 87 Ai Ni

The U 87 is probably the Neumann studio microphone best known and most used in the world. It has a capsule large dual-diaphragm with three directional patterns: omnidirectional, cardioid and bidirectional (figure-8), selectable via a switch located under the grid.

An attenuation of 10 dB selector is located on the rear of the microphone; it allows him to cash undistorted sound pressure levels up to 127 dB SPL.

You can also reduce the bass response to compensate for proximity effect.
Applications
The condenser microphone U 87 Ai is a model membrane of large diameter, with three different directivity, and with unique characteristics in terms of frequency response and transient.

Users immediately recognize this microphone thanks to its very special look. It is a good choice for most common applications in studio, broadcast, film, television ...

The U 87 Ai is also used as a main microphone for orchestra recordings, extra on isolated instruments, and most common way, as micro voice on all types of music (singing) and spoken voice.
Acoustic characteristics
The U 87 Ai is a side-effect model - the Neumann logo is placed facing the sound source. For cardioid and bidirectional, the frequency response is very flat for frontal sound incidence, even in the treble. The microphone can be placed very close to a sound source, without becoming aggressive. His high pass filter attenuates with remarkable efficiency, subsonic interference in the matter.
Directional
The double diaphragm capsule is elastically mounted and protected by a grid of large dimensions. The selector placed under the grid allows to choose between the three directional patterns: omnidirectional, cardioid and biddirectionnelle (Figure 8). The directivity corresponding to the selected icon is displayed in a small window above the dial.
Electrical Characteristics
The letter A from the reference indicates a newer generation compared to the U 87 i models manufactured from 1967 to 1986. The changes concern only the electronic components of the microphone: the capsule itself remained unchanged.

The current system increases the operational headroom of the U 87 Ai by passing the capsule bias voltages by a lower resistance value. The result: increased sensitivity of 10 dB for the same level of sound pressure and a report signal / noise by 3 dB higher.
Filter and attenuation
A selector located on the rear of the microphone reduces sensitivity of 10 dB. When activated, the microphone accepts sound pressure levels up to 127 dB (equivalent figure to a sound pressure of 45 Pa) without distortion.

Another switch at the rear allows to change the microphone's cutoff frequency. It reduces harmful interference directly at the input of the integrated microphone preamplifier.

This switch also compensates the inevitable boost in the bass, common to all pressure gradient transducers when used in small distance from the sound source (proximity effect).

The cardioid frequency response remains flat up to a distance of 30-40 cm - 15 to 20 cm for bidirectional directivity