Alan Blumlein: The Inventor You've Never Heard Of (But Use His Technology Every Day)

By Spencer Hart on at

On Wednesday (April 1) some of the most influential sound engineers of past and present gathered at Abbey Road Studios to celebrate the ground-breaking work of Alan Dower Blumlein. If you haven't heard of Blumlein (pronounced Bloom-line) before, you've certainly used his technology, because in the 1930s he invented a way to record and playback stereo sound.

Blumlein received a posthumous Milestone Honour from the Institute of Electrical and Electronics Engineers (IEEE), not only for inventing stereo sound, but also for his contributions to telecommunications, television and airborne radar.

Inventing Stereo Sound

In 1931, Blumlein and his wife were at a local cinema, frustrated at the fact the cinema only had a single loudspeaker, Blumlein stated:

"Imagine a blind man looking at the screen, he couldn't tell where anybody on the screen was speaking, although they may be walking across the screen, the sound is just coming from the loudspeaker. But I have a way, and I'll be able to make that sound move with the person across the screen, so although the blind man can't see the film, he could imagine the scene."

Later that year Blumlein filed a brief 24-page patent titled 'Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems'. It's a document that continues to be referenced today.

The 24 pages contained no less than 70 new claims, including the complete, end-to-end stereophonic system. People had tried to make stereo microphones, and loudspeaker arrays before, but Blumlein was the first to develop an end-to-end system. This included the stereo microphone, recording system and speaker array.

Stereophonic Technology

The microphone set-up that Blumlein used to record stereo sound is now called the 'Blumlein Pair', although it wasn't called this during his lifetime. The Blumlein Pair consists of two bi-directional microphones, positioned 90 degrees from each other in the closest proximity possible (usually on top of each other).

These microphones record a figure-of-eight pickup pattern (illustrated above), this records a high-degree audio separation in the source signal as well as the room ambiance. [Image Credit: Wikipedia]

Each microphone records to a different channel, and Blumlein also devised a way to record these two channels of sound into a single groove of a record. He did this by using the two groove walls at right angles to each other and 45 degrees to the vertical to carry the different channels. The horizontal stylus motion conveys one signal, while the vertical stylus motion another signal. Despite Dower patenting this system in 1933 while working at EMI, it was not applied commercially until around 25 years later when a company named Westrex began engineering LPs in the US.

His Short Films

It was decided that Dower's work would be more beneficial for cinematic use. Some of his short test films are still in existence today.

Both 'Trains at Hayes Station' (above) and 'The Walking and Talking Film' (below) demonstrated Blumlein's original intent of allowing partially sighted people follow the scene.

Television and Radar Work

Not content with revolutionising sound engineering, Alan Dower Blumlein also worked on telecommunications, television and radar. Blumlein started his career at International Western Electric, where he designed the first weighting networks, a loading coil which reduced crosstalk, and the 'Blumlein Bridge'.

He then went on to work at the Columbia Gramophone Company which later became EMI. During his time at EMI, Blumlein worked on a number of research teams, including sound recording and television. His work on television technology included resonant flyback scanning, black-level clamping and the slot antenna.

While at work, when Alan was at the top of signal towers, he would often call his wife, Doreen, to ask her opinion of the picture quality and reception as he made changes. They were simpler times!

Perhaps Blumlein's most important work however was his development of the H2S radar system. H2S was the first airborne, ground scanning radar system, and Alan aided development of this during the second world war. The system was designed to identify ground targets for nighttime and all-weather bombing raids.

Blumlein's Death

Blumlein was tragically killed during a test flight of the H2S radar system on June 7, 1942. The Halifax Bomber he was working on caught fire mid-flight, and crashed near the village of Welsh Bicknor in Herefordshire. This was the result of a nut that was loosened during a routine engine inspection held just three hours before the flight.

There was also fears that his death would result in the termination of the H2S project, but this was not the case. Winston Churchill ordered that Blumlein's death should not reported straight away as part of the British government's wartime secrecy, even his relatives were not told the cause of the crash.

[Featured Image Credit: Universal Music Group]