Telephone engineering

In September 1924 Blumlein's industrial career began when he joined International Western Electric (now part of STC). Telephone networks were growing nationally and internationally and his first task was to look at interference caused by electric power lines. His boss, John Collard, "at first found him somewhat raw and a difficult person to take to meetings". He could also be very rude, having little patience with anyone less brilliant than himself and being intolerant to those who would not work all hours as he did. Time mellowed him, however, and according to Collard, "he acquired a certain amount of tact". Philip Vanderlyn remembers the same man at EMI, but twenty years on, quite differently. "He would keep in daily touch with all the work in the laboratories, and he would talk with the most junior of us as equals without ever making us conscious of our lack of status, which was good for our egos and even better for our technical education. In this task of training his staff he had unbounded patience."

Two years after joining International Western Electric Blumlein was asked to solve the problem of crosstalk in telephone loading coils. His success brought him a bonus of £250, which was £25 more than his starting salary. The work also led to his first patent (with J.P. Johns) and to the first of his many inventions: the tightly-coupled inductive ratio-arm a.c. bridge (above). One of the its uses was for measuring small capacitances in the presence of much bigger capacitances to earth, but Blumlein was forever finding other applications. During the war he used it as an aircraft altimeter.

Audio recording

Blumlein was soon looking for wider horizons and so he moved to the Columbia Gramophone Company in March 1929. According to Benzimra Blumlein told Isaac Schoenberg, the general manager, that he might not still want him when he heard the salary he was asking. Schoenberg’s reply was to offer him even more!

By that time the knowledge and skills slowly acquired by telephone engineers had been applied to make a new audio disc recording method which made mechanical systems obsolete. Any record company that stuck with the old techniques would soon be obsolete too. The patents for the new method were held by the Bell System (Western Electric) in America to which a royalty was paid for every record pressed. Blumlein was given the task of inventing an alternative electrical method which would not violate the American patents.

To do this he adopted the moving-coil principle which the Americans had not used. He and his colleagues are known to have been working on the design in October 1929 and a prototype was tested the following February. Electrical damping replaced mechanical damping to control the resonance of the cutting head and, with electrical filters, a wide frequency range was achieved with excellent linearity. A complete system was designed and built in-house, from new moving-coil microphones through the intermediate electronic circuitry to the final moving-coil recording head.

The first recordings were made in 1930 and they set a new standard for fidelity. Blumlein received a £200 bonus. But his thoughts had by now ranged beyond others' horizons to consider how a spatial impression of the artists' performance could be achieved using only two loudspeakers. He took out an incredible patent in 1931 with seventy claims relating to 'binaural' recording - in other words, stereophony. He was 25 years old at this time. When stereo records became a commercial reality in the 1950s EMI received nothing from this patent. Even after an extension, the patent had expired.

Blumlein's system was intended primarily for cinema use, but it also included records and was essentially that used for stereo records from the mid-1950s. The only widespread use that Blumlein lived to see was one of the few applications not covered by the patent. In World War Two a couple of thousand stereo sound locators were made for assisting in aircraft detection. With previous systems nearby gunfire could deafen the operators. Blumlein electronically limited the sound and used a cathode-ray tube (instead of earphones) for indicating the results.