neumann.berlin
the microphone company
M 50 – The Historic Omni Directional
At the same time as Neumann launched the M 49, the first
remotely controlled microphone, Neumann also introduced
a new omni directional microphone, model M 50. This microphone distinguished itself by not merely using a pressure transducer as its pickup, but also by mounting this
capsule in a spherical body with the diaphragm flush with
the surface of the sphere. Unlike a conventional cylinder
shaped omni directional microphone, the arrangement of
the capsule and sphere provides a different behavior in the
sound field. As result the microphone has a very smooth
frequency response to above 1000 Hz with a gradual rise
reaching +6 dB from 8000 to 16000 Hz. Simultaneously,
the directional characteristic shows an increasing directivity toward the higher frequencies. The unique feature of the microphone is
its high frequency directivity, similar to that of a pressure gradient type, combined with the linear response at low frequencies,
well known for pressure microphones.
Mechanically the M 50 is
constructed like its sibling
model M 49. The amplifier
is elastically mounted on a
solid rubber plate, while
the microphone capsule is
mounted in its Plexiglas
sphere on the plastic amplifier cover via an elastic suspension. As the active element a Telefunken triode
of the type AC 701 (k) is used. Originally the microphone
capsule was equipped with a highly stretched aluminum
diaphragm, later versions employ gold sputtered polyester
foil. In order to achieve a high sensitivity and low equivalent noise level, the separation between diaphragm and electrode is an extremely narrow 10 µm. By comparison, this
distance is typically more than twice as large with other
condenser capsules.
The M 50 microphone was very quickly accepted as the
high quality microphone for all classical recordings, as spot
microphone for woodwinds and brass, but also for strings.
An interesting experience was reported from a recording
studio in Berlin, where two M 50s were placed as spot microphones in front of a violoncello at a distance of 2,5 m.
The optimum sound was achieved with both microphones
turned off axis by approximately 15°. Thus the directivity
of the M 50 was used as a sound defining element.
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