Neumann History

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 technology 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 particularly significant when it is considered that by 1930 Neumann had already made the transition 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 recognisable shape. Diversification brought continued innovation, ranging from electro-acoustic measurement equipment to cinema gongs and station identification code signals (used by broadcasting companies to broadcast their station identification) to standard linear microphones.

Neumann also developed a pistonphone for calibrating 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 exceptionally high degree of accuracy.

His Most Important Invention?

It was during the course of this widening development work that Georg Neumann made his most important contribution to modern electrical 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 consisting essentially of cadmium, cadmium oxide and a nickel anode. These cells had a comparative capacitance of 100 to 160,000 µF at a frequency of 50 Hz, depending on the size of the cell, and Neumann was able to use them to stabilise the heating voltage for condenser micro- phones.

Their outstanding filtering capacity was extremely 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 discovery 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 voltage 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 diaphragms 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.

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