Introduction to the Edison Diamond Disc
The Edison Diamond Disc is unlike nearly every other record ever made. About a quarter-inch thick, 10” in diameter, and weighing close to one pound each, they revolve at 80 rpm and were recorded using the vertical “hill and dale” method in which the bottom of the groove rose and fell, producing the vibrations on the diaphragm to create the sound. A permanent diamond stylus tracked the bottom of the grooves, and the diaphragm was mounted parallel to the surface of the record.
Edison records cannot be played on most other phonographs. Any machine using a steel needle (all Victor and Columbia machines) will quickly and severely damage an Edison record. A couple of manufacturers (such as Brunswick and Pathé) had reproducers that could be mounted vertically, and used a sapphire ball which can safely play an Edison disc, though not as well as a genuine Edison machine.
Because the vertical recording method required an absolutely flat surface, the manufacture of Edison discs was quite involved. They were made up of a core of compressed wood flour (later China clay) with a layer of “Condensite” (a phenolic resin varnish) bonded to the surface on which the recording was engraved. While this produced a very quiet recording, moisture often caused this bonded layer to separate or develop raised “lamination cracks” rendering the recording useless. After mid-1916, this layer of resin varnish was applied directly onto the core. While it eliminated the peeling and cracking, it resulted in considerably higher surface noise that took Edison another four or five years to bring under control.
The earliest Diamond Discs made from 1912 through early 1916, when in good condition, are simply outstanding. Their surfaces are whisper quiet and the frequency range for an acoustic recording is quite wide. In mid-1916, due to the new manufacturing method and a shortage of phenol, the record surfaces deteriorated, and from late 1916 through early 1919, surface noise is quite high, even on records that are in nearly new condition. Edison added heavier layers of resin varnish, and improved the core, and slowly over the next few years the surfaces improved. By the early 1920s the records again were close to the original standards.
The sound of Edison discs is unique. Due to his hearing issues, Edison did not like the ringing and reflected sound which was evident on most other disc recordings. He called it the “Victor ear tickle.” So Edison recordings were made in a “dead” studio that had no reverberated sound. While it takes away a bit of ambiance from ensemble recordings, solo instruments sound amazingly realistic. In fact, a violin or cornet solo on a good Edison recording sounds as if the player is actually in the room. It was this incredible fidelity that prompted Edison to rename his discs “Re-Creations.”
Probably the greatest handicap under which Edison Diamond Discs suffered was the choice of repertoire. Edison, while a gifted inventor, was not a great businessman and often meddled in areas best left to others. As the self-appointed Musical Director, he imposed his own personal tastes on the catalog. Seeing as he was nearly deaf, he was probably not the best choice for that job.
Despite these limitations, Edison discs have sound unlike any other, and were able to preserve music from the 1910s and 1920s with a fidelity unmatched until the advent of electrical recording in 1925.
-Michael Sherman, Monarch Records Enterprises (Michael is the author of the reference work The Collector's Guide to Edison Disc Recordings.)