STEREO TRANSMISSION AND RECORDING.

In 1924 Ludwig Kapeller made some notable improvements on Ader’s system, although he made no attempt to record. He also passed along Ader’s term. Describing his “plastic tone reproduction” system, he said: “This procedure is called stereophony.”

A number of U.S. broadcast stations also experimented with stereo notably WPAJ New Haven, Conn. Around 1925, it applied for and received permission to transmit on two separate frequencies, 1110 KHz and 1320 KHz. However, this meant that listeners had to have two radios and connect each one to head phones. Few people had even had one radio. So the work was abandoned.

Stereo really got its start in 1931, when the British designer A. D. Blumlein received a patent for a system of recording on phonograph records. The method was so highly sophisticated that it is still used by EMI (Electrical and Musical Industries) in Britain.

Developments then began to come more rapidly. In 1936 Bell engineers patented a type of disc-cutter that is still used for our 45-45° microgroove records. Then in 1939 Bell laboratories came up with stereo tape recording. In 1941 we saw and heard the first stereo-sound film, Walt Disney’s Fantasia. Then however the war intervened.

The step was the announcement of a true stereophonic record by audio engineer Emory Cook (later of Cook Record fame). The performance, picked up by two microphones was recorded on two separate sets of grooves: one set near the edge, the other near the centre of the record. The records were played with a two cartridge arm. Tracking difficulty, however, ruined this idea.

In 1949, Magnacord demonstrated a stereo home tape recorder. In 1954, stereo tapes appeared on the market and within few years came 4 track and 8 track tape for the home.

What about stereo broadcasting? As the number of FM receivers increased, a few stations began broadcasting one channel on their FM station, the other on the AM station. Listeners placed their receivers a distance apart and heard stereo. Most stations, however, did not want to ruin the program for their AM listeners who were in the majority. So what we call “separation” was pretty much absent. A much larger portion of the music went out over the AM station and little was left for the FM receiver.

There were demands for “compatible” stereo broadcasting and research was undertaken for a way to send both stereo channels over one channel. In 1958 Murray Crosby, who had worked with Major Armstrong in the development of stereo systems, received a patent for such a system and in May 1967 an even broader one.