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 mi-
crophone distinguished itself by not merely using a pres-
sure 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 directiv-
ity toward the higher fre-
quencies. The unique fea-
ture of the microphone is
its high frequency directiv-
ity, similar to that of a pres-
sure gradient type, com-
bined with the linear re-
sponse at low frequencies,
well known for pressure mi-
crophones.
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 ampli-
fier cover via an elastic sus-
pension. As the active ele-
ment 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 equiva-
lent noise level, the separation between diaphragm and elec-
trode 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 mi-
crophones 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.
