Neumann U87 Ai MT

The U 87 is probably the best known and most widely used Neumann studio microphone. It is equipped with a large double diaphragm capsule with omnidirectional, cardioid and figure-of-eight polar patterns, which are selected via a switch on the capsule head. A switch at the rear provides a 10 dB pre-attenuation. This allows the microphone to transmit sound pressure levels of up to 127 dB without distortion. Furthermore, the frequency response can be reduced in the low frequencies, e.g. to compensate for the proximity effect. Range of applications The U 87 Ai condenser microphone is a switchable large diaphragm microphone characterised by its transmission properties, various switching options and attractive shape. It is equally suitable for a large number of applications in radio, television, film and sound recording technology. In orchestral recordings it is used as the main microphone and as a support microphone for individual instruments, but mainly as a vocal microphone in all types of music. Acoustic characteristics The pick-up direction is sideways, with the front side being characterised by the company label. The frequency response for the cardioid and figure-of-eight characteristics is practically linear, even in the upper audio frequency range for frontal sound incidence. This means that the microphone can be used at a short distance from the sound source without producing an unnaturally sharp sound impression. An electrical high-pass filter cuts off low-frequency sound as a measure against background noise. Directional characteristics The elastically mounted double diaphragm capsule is surrounded by a large wire mesh basket. The omnidirectional, cardioid or figure-of-eight polar patterns can be set using a switch below the basket. A window above it displays the setting in symbols. Electrical characteristics The additional letter A in the designation indicates a change in design compared to the U 87 i microphone supplied from 1967 to 1986. This change relates to the electrical part of the microphone; it makes the U 87 Ai more reliable due to a lower impedance supply of the capsule bias voltages, increases the transmission ratio by approx. 10 dB at the same sound pressure level and improves the signal-to-noise ratio by 3 dB. Filter and pre-attenuation A 10 dB pre-attenuation can be set using a switch on the rear panel. The microphone is then able to transmit sound pressure levels of up to 127 dB (corresponds to a sound pressure of 45 Pa) without distortion. If another switch on the rear panel is activated, the lower cut-off frequency of the microphone is raised and low-frequency noise is attenuated at the input of the microphone amplifier. The unavoidable increase in bass at close range with pressure gradient receivers is compensated for in such a way that a flat frequency response is achieved at a distance of 30 to 40 cm in the cardioid position and at a distance of 15 to 20 cm in the figure eight position.