Neumann History
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More than Just Microphones ...
By 1928 Neumann had spread his attention to
other aspects of studio engineering, such as
record making. It was his interest in record tech-
nology that was, in fact, the real reason for the
split with Eugen Reisz.
His enthusiasm and Reisz’ opposition were
stirred by a commission from Neumann’s friends
in England to build a machine for cutting
records. This machine was to become the basis
for Georg Neumann & Co’s secondary line of
products.
The earliest disc cutting machines were belt
driven. The head was moved forward by a spin-
dle, which was itself driven via
a worm gear and a further gear
from the base of the turntable.
The obvious parallel between
this configuration and later
record playing deck is particu-
larly significant when it is con-
sidered that by 1930 Neumann
had already made the transi-
tion from belt drive to direct
drive with the motor acting as
a direct extension of the turn-
table spindle.
Throughout the ’30s and early
’40s the company began to take on a recognis-
able shape. Diversification brought continued
innovation, ranging from electro-acoustic meas-
urement equipment to cinema gongs and sta-
tion identification code signals (used by broad-
casting companies to broadcast their station
identification) to standard linear microphones.
Neumann also developed a pistonphone for cali-
brating both standard and pressure microphones.
The pistonphone generated a sound pressure
which could be controlled optically with great
accuracy within the 20 Hz to 600 Hz range via
the movement of a piston which displaces a giv-
en volume of air. The amplitude of the piston
was observed through a microscope, enabling
the microphones to be calibrated to an excep-
tionally high degree of accuracy.
His Most Important Invention?
It was during the course of this widening de-
velopment work that Georg Neumann made his
most important contribution to modern electri-
cal engineering. In 1947 he de-
veloped a process by which
nickel-cadmium batteries could
be made without the excessive
formation of gas and so totally
gas tight – an invention that has
direct links with virtually every
modern electronic apparatus.
Flash units, hearing aids, camer-
as, radios, etc, all rely on minute
nickel-cadmium batteries, whose
availability is the result of this
development.
One of the by-products of Neumann’s process
were stability cells, containing a cathode con-
sisting essentially of cadmium, cadmium oxide
and a nickel anode. These cells had a compara-
tive capacitance of 100 to 160,000 µF at a fre-
quency of 50 Hz, depending on the size of the
cell, and Neumann was able to use them to sta-
bilise the heating voltage for condenser micro-
phones.
Their outstanding filtering capacity was ex-
tremely useful for filtering the heating current,
particularly for directly heated tubes.
The Big Success
In retrospect, 1947 was a prolific year for the
Neumann company. On top of one major discov-
ery the company launched the
microphone that has probably
had the greatest influence in the
development of modern studio
microphone technology. The U 47
was the first switchable pattern
condenser microphone. Its im-
pact, especially in America, was
such that the dominance of
RCA’s ribbon microphone as the
studio standard was eclipsed.
The U 47 had a double diaphragm
capsule. Both diaphragms could
be polarised with the same volt-
age or neutralised with respect
to the centre electrode, so that
the omnidirectional and cardio-
id characteristics were adjusta-
ble. A ‘special’ (U 48) was also
produced, in which the dia-
phragms could be polarised with
opposite voltages with respect to the centre elec-
trode, so that it was possible to switch between
cardioid and figure-of-eight directional charac-
teristics.
