Hifi History: The invention of Stereo
When writing about this outright delightful 1958 RCA promotional video regarding the advent of “Living Stereo”, many viewers were as happy as I was to have seen it, with one notable exception. One reader rightfully called RCA out as impostors for indirectly claiming to have invented both stereo sound and the stereophonic record groove and rightfully pointed me to the work of Mr. Allan Blumlein 25 years before their outlandish claim. It turns out that Blumlein is somewhat the Nikola Tesla of the audio world in the sense that he was far ahead of his time, had remarkably innovative ideas, and deserves much more credit than he has ever been given. Certainly a story worth writing about, I thought.
Alan Dower Blumlein born in 1903 London is said to have gone to the movies with his wife Daureen one day in 1931. He was not impressed. It is not known what movie the two saw but his grievance was hardly with the quality of the screenplay. What Blumlein did not like was that the actors on the screen seemed to be talking from a place where they weren’t physically located. Blumlein at the time already a highly prolific inventor who would eventually have 128 patents under his belt upon his untimely death in 1942 thought he could fix that.
Blumlein had already studied human hearing for quite some time during his work on advancing transmission quality of the telephone and came up with an idea he named “binaural sound”. This was not an easy feat at all as it had to encompass the entire process from recording to storing the sound to reproducing it faithfully.
The way Blumlein resolved the recording dilemma was by means of a pair of matched bidirectional microphones arranged in a 90 degree relationship to each other. This became known as a Blumlein pair and is still in use today.
The storage on phonograph records was another complex task and while RCA simply pretended in this 1958 promotional video that they had invented the stereo groove. Blumlein was several decades ahead of their use of the technology.
The idea of having one single groove encode the right channel at 45 degrees and the left channel at -45 degrees was so complex and mathematically difficult to describe that Blumlein simply built this outright ingenious model to convince his bosses at EMI to let him do additional work on it:
The last part of the chain seems very simple now, but was anything other than banal at the time. We have now simply accepted the truth that a somewhat three dimensional stereo field can be reproduced by super imposing the sound of two or more loudspeakers. The human hearing then takes minute cues from differences in inter-aural loudness, phase delays, group delays and the relationship of the overtones to the fundamental signal to determine a more or less precise location for the origin of a sound that has been recorded and stored
What we now perceive as so intuitive a truth, was completely obscure in Blumlein's time and he did extensive experimentation into how human hearing works as this very charming video shows.
In 1934 this remarkable stereo recording was created in a single groove record at Bell Laboratories. Blumlein was using a vertical / lateral Blum
lein microphone pair, and this clip shows the outright astounding audio quality for the time including great stereo separation.
By the time he was ready to convince his bosses at EMI to market this to the movie industry, he had 70 patents and innovations under his belt and had certainly accomplished something that has changed our lives for the better. The first movie featuring stereo sound was technically exiting, albeit dramaturgically a let down. The film “Trains at Hayes” was simply shot from a window in the EMI offices in Hayes, West London in 1935 onto the local train station to test this new technology.
In 1934, Blumlein at that time at Bell laboratories recorded Mozart's Jupiter Symphony conducted by Sir Thomas Beecham at Abbey Road Studios in London. By all means click the link provided as the sound quality and stereo separation are really remarkable given time and circumstance.
Blumlein went on to work in television for a while, convincing the world to favor an electronic solution rather than a mechanical one, but as we all know the world burst into flames in 1938 and the finer things of audio and entertainment were put on the back burner as England's need to defend herself became increasingly pressing.
During the war, Blumlein got involved in the development of radar. The H2S radar system was designed as an aircraft based air to ground radar system to allow for all-weather-bombing.
The H2S radar system was highly successful and lived a much longer life than its inventor Alan Blumlein. Almost all Bomber Command aircraft during the late war period and beyond were equipped with H2S radar systems. An advanced version, the Mk. 9, was developed for the post-war V bomber fleet. The last war use of H2S was in 1982 during the Falkland conflict to avoid flying into the Avro Vulcan, and some units remained in service on the Handley Page Victor aircraft until 1993.
Blumlein however was not blessed to see the success of most of his inventions. An HS2 equipped aircraft engine caught on fire during a 1942 test flight and Alan Dower Blumlein perished along with the rest of the flight crew.
The last of the good things that came from Blumlein’s remarkable life was a directive issued by Winston Churchill himself, that all future test flights carrying civilians and scientists were to be equipped with sufficient parachutes for all individuals aboard.
Arved Deecke is founder of the Danish / Mexican Loudspeaker company KVART & BØLGE that makes audiophile quarter wave loudspeakers and sound systems at a price anyone can afford. In his free time he blogs about all things related to sound, music and audio.
