In
1949, Dr. Herbert Grosskopf of the IRT (Institute Fur Rundfunktechnic, a
German-based technical standards and design organization established after WW
II by German broadcasters) designed and patented the first electronically
remote-controlled variable pattern condenser microphone, the M49. This design
was given to Neumann for manufacture, and Neumann incorporated its
well-established M7 capsule into the mic. The IRT also wanted to establish a
standard tube amplifier for all German broadcast mics and a special low-noise,
hand-built tube; the Hiller MSC2 was developed for this purpose. Telefunken
manufactured the final version of this tube as the AC701K, and eventually, all
condenser tube microphones in the German broadcast system used this tube. The
"M" designation before the model number indicated the standard
AC701K amplifier, while the "U" designation indicated other tube
amplification. The unique taper of the windscreen grille shows a major effort
to address the influence of grille resonance. The M50, a look-alike twin of
the M49, shares the design shape and the AC701K tube, but it is strictly a
pressure microphone designed for distant orchestral miking work. Its small
pressure capsule evolved through three separate diaphragms, first with PVC,
then aluminum (the same as the KM53), and finally with gold-sputtered Mylar.
The diaphragm was flush-mounted in a plastic sphere designed to allow the
capsule to respond with some directional characteristics in the frequencies
above 1 kHz while still maintaining an omnidirectional characteristic at the
lower frequencies. An additional +5 dB of high-frequency boost was added in
the AC701K tube amplifier circuit, resulting in a favorable overall frequency
response when the mic was used at a distance from its source.