Neumann M 49 User Manual

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M 49 – The First Remote Controllable

An important step forward in microphone technology was
made with the model U 47. Its dual diaphragm capsule
M 7, active on both sides, made possible the first condens­er microphone with switchable polar patterns. The ques­tion arose, whether it could be possible to change the char­acteristic during recording.

The relevant patent of Dr. Grosskopf reads: “Thus... the
influence of exaggerated re­verberation can be dimin­ished ... the recording dis­tance ... can be increased
without getting a vague tim­bre ... It is therefore an ur­gent need for the recording
technique to easily exchange
microphones with different
polar patterns ...” The objec­tive was to avoid an exchange
of microphones or capsules
and to remotely control the
microphone’s directional
pickup pattern. For this pur­pose it is important that the
output of the microphone
remain fairly constant and independent of the selected pat­tern. The only switchable pattern microphone existing at
that time, the Neumann U 47, exhibits an increase in the
output by 5 dB when switched from omni to cardioid. In
the cardioid position the rear half of the capsule in the U 47
was simply electrically disconnected. As a consequence, the
output of the rear capsule and the attenuation of the front
via the fixed parallel capacitance of the rear were avoided.

“Comfortable” pattern con­trol for the new M 49 micro­phone was achieved by keep­ing both capsule halves con­nected to the impedance
converter with regard to the
signal, however, insulated
from each other with regard
to the DC bias. The front di­aphragm is polarized with a
constant voltage of 60 Vdc,
while the bias for the rear di­aphragm is adjustable from
0 Vdc to 120 Vdc. This al­lows the polar pattern to be­come variable between omni through cardioid to figure-8
maintaining a practically constant sensitivity. The power
supplies for the model M 49 microphones included a po­tentiometer with a pointer knob and a corresponding scale.

Available were portable and rack mounted versions of the
power supplies. Due to the many supply voltages the M 49
microphone was equipped with an 8-pole connector. As
tube, in the early versions, a directly heated triode MSC 2
made by Hiller was employed, which later was succeeded
by the Telefunken AC 701 (k). The mechanical construc­tion provided means for the suppression of structure born
noise. The amplifier was mounted on a solid rubber disk,
mechanically isolating the amplifier from the housing. In
addition, the microphone capsule was mechanically decou­pled by means of a swing-metal shock mount. This meth­od was incorporated later in most of the succeeding Neu­mann microphones.

The M 49 was introduced to the German Radio Broad­casters in 1952. Because of its unprecedented versatility it
conquered the international recording studios rather quick­ly. Due to the innovative feature “remote pattern control”
it found widespread application as the important main mi­crophone above large orchestras. Other applications were
as a spot microphone for wind and string instruments, for
piano and as the favorite announcer’s microphone.