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The secret stereo of the Edison phonograph

Edison may have invented the phonograph, but stereo records didn't come along until a while later. But perhaps Edison's recordings have a secret stereo soundtrack that no-one has yet been able to hear.


Edison may have invented the phonograph, but stereo records didn't come along until a while later. But perhaps Edison's recordings have a secret stereo soundtrack that no-one has yet been able to hear.

There is no doubt that Edison had one of the world's greatest creative minds, and his invention of the phonograph created the sound engineering and recording industry as we know it today. Edison's original cylinder phonograph was quickly superseded by Emile Berliner's disc, but the essential principal of recording remained the same.

Many great recordings were made during the early era of the phonograph, of artists who deserve to be heard today. Until the 1950s and the maturity of the tape recorder, recordings were cut directly to disc. Often, the cutting lathe would be in the same room as the performers; the separate control room as we know it now was yet to be invented.

But the sound quality was poor, and of course in mono, not the glorious stereo we expect today.

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With modern technology, much can be done to improve the quality of an old recording. The CEDAR system can remove clicks and surface noise incredibly well; lost frequencies can be equalized and boosted. There is even emerging technology that can correct the harshness of distortion, and that is correct it - not merely filter it out and lose much of the wanted sound in the process.

No modern technology can create stereo from mono. It is possible to fake a stereo effect, but it remains fake and reveals no further information from the original recording.

But there may be an additional source of information locked in the grooves of these early, supposedly mono, recordings.

Imagine the musicians in the recording room (the word 'studio' had yet to be coined). The sound they create passes into the recording horn or microphone and is cut as a side-to-side horizontal modulation - 'wiggle' - in the groove. But simultaneously, the sound is creating a vibration in the floor beneath the musicians that will pass through to the plinth of the cutting lathe and vertically upwards into the turntable. In turn this will pass through to the blank disc, which will vibrate vertically under the cutting stylus. Thus, this additional signal is cut as a vertical modulation of the groove, at right angles to the conventional signal, and is present in discs manufactured from these original recordings to this day. (That vibration can pass from floor to turntable is well known in hifi design. Modern high-quality turntables either have a sophisticated absorbent suspension, or are mounted on a solid slab of granite or similar material).

Plainly, the sound quality of this additional unexpected signal will be comparatively poor, and will not form conventional left-right stereo as we would choose today. But if carefully extracted from the groove, and processed in an appropriate way, it would add massively to the subjective experience of listening to these old and often great artists.

The only way to find out whether or not this is practical will be to conduct very careful and precise tests. On some recordings, it will not work at all. On others, the additional information might be insignificant. But perhaps on a minority of discs, we will be able to hear music gloriously performed in stereo, which we - and Edison and Berliner - never even imagined could be possible.

Is the ghost of Thomas A. Edison listening perhaps?

By David Mellor Wednesday September 21, 2005

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