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Stereo Disc Today

By SIDNEY FREY

Pretident, Audio Fidelity, Inc.

Summary of presenł status of stereo discs by one of the leading disc manufacturers.

IT’S difficult to believe that it is hard-ly a year and a half sińce the stereo disc madę its commercial debut on the American scene. The impact of this innovation in musical reproduction has been nothing short of sensational. Nothing in sound has caught the publice fancy as has stereo sound on rec-ords. There are few Americans today who havc not heard the exciting sound of stereo—somewhere, at some time— yet "Marching Along with The Dukes of Dixieland”, the first commercial stereo recording, hit the market less than 20 months ago!

Early History

Stereo has come a long way sińce the first stereo transmission of musie back in 1881 when the then-new telephone was used to transmit programs from the stage of the Paris Opera. The audio engineers of the time used a pair of telephone lines—one for each ear—to create the stereo effect.

Application of the stereo techniąue to recorded musie on discs came in 1931 when A. D. Blumlein, an engineer employed by Electricul and Musical Industries, Ltd. (EMI), filed for and re-ceived British patents on a system for cutting and reproducing both vertical and lateral tracks on the same disc. In 1936. A. C. Keller and I. S. Rafuse, engineers at Bell Telephone Labs, developed a similar technique and were granted U. S. patents. At this point, stereo as we know it today, meant lit-tle to anyone except those specializing in the field. There was no excitement, no rush to get on the bandwagon, no scurrying in an industry that was, at that time. in its infancy and struggling to survive.

In 1952, Emory Cook introduced a binaural disc having two independent channels. one track on the outer half of the record and the second track on the inner half. The record was played by means of an odd-shaped pickup arm which had two cartridges mounted side by side.

This system was ingenious in its ap-proach to a solution of the two-channel problem. The resultant sound was good. However, difliculty in adjusting the arm and cartridge for proper tracking and the fact that only half as much program materiał could be ac-commodated on the disc precluded wide public acceptance of this so-called binaural system.

The birth of the stereo disc, as we know it today. did not take place until the fali of 1957. At that time British Deccu (London) introduced a single-groove recording to the United States. Both channels were cut into one groove —one laterally and the other along the bottom. The London system was vul-nerable sińce the output of the two channels, each cut differently. were conceivably different in charactcr.

The Westrex Co., manufacturers of recording equipment, operating in-dependently. produced another varia-tion of this two-channel, single-groove cutting technique. This variation con-sisted of rotating the groove relation-ship 45° to the record surface. thus overcoming the objection to the London system.

Westre.r designed its cutter with two vertical cutters linkcd together. their axis forming a 90° angle and couplcd to a single Stylus in such a way as to make cuts for each channel at 45° to the disc surface. For playback, the company specified two lateral cartridges coupled together in a similar manner.

It was at this point that we at Audio Fideliti/. using a master prepared for us by Westrex, produced the first commercial stereo disc. The program materia! was “Marching Along with the Dukes of Dixieland" and "Railroad Sounds”. which we had previously re-leased as a stereo tape. Surprisingly, the quality of this pioneer record was of a high order. Ali the elements were there: wide channel separation, dynamie rangę, and good frequency re-sponse. The one thing that was lacking was a cartridge with which to play the recording. Up to that point, the only availab!e stereo cartridge was a hand-made unit which We*trex was using to demonstrate the output of its cutting equipment.

Actually. it was some time after this first stereo disc was pressed that mem-bers of our own organization were able to hear the results. At that time we were able to listen to a stereo playback with one of the first Fairchild 603 playback cartridges. These units were hand-made and the cartridge and arm assembly sold for $250.00.

lmprovemenfs & Problems

The rest is history. The original Westrex 3A cutter was succeeded by the 3B and then the 3C. Each was a slight improvement over its predeces-sor. Certain resonant peaks were re-moved and variable vertical pitch was introduced. The latter was a device which cued the cutting head to cut deeper to prepare for passages with wide dynamie rangę.

Each development helped to improve

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