The Mapleson Cylinders - Program Notes
|The Mapleson Transfers|
by Tom Owen
The first order of business was to design a playback apparatus capable of accommodating cylinders of all types, that imposed no mechanical vibration, offered light-weight tracking, accommodated speeds from 40 to 200 rpm, could be servo-driven, had digital mandrel readout in rpm, and could track vertically with no side angling at 100, 150 and 200 lpi (lines per inch). Obviously, this was no small order. Art Shifrin, a restoration engineer, developed a machine which accomplished most of these goals, and with further modifications at Rodgers and Hammerstein, it was able to fill our needs.
I made a search of the existing literature on the analysis and playback technology of acoustical recordings--an area that proved to be under-investigated. (This was before the Audio Engineering Society published their index of publications.) However, an article by Hans Meulengracht-Madsen, "The Transcription of Old Phonograph Wax Records" ( AES Journal, XXIV/1 ) describes an extremely thorough acoustical analysis methodology, and should be required reading for anyone working with this technology. It is based on cylinders recorded from 1919 to 1923, 23 years after Mapleson did his recordings. My associate John Fesler and I knew that in order to do viable acoustical analysis, the cylinders would have to be recorded methodically, under calibrated conditions, on equipment similar to that used by Mapleson. This was not difficult, since many Edison Home Model A's are still to be found in good working condition. We will discuss the recordings and their setup in a moment, but first let me discuss the acoustical concerns.
One of the most important articles to date concerning acoustical analysis is that of Maxfield and Harrison (in the Journal of the American Institute of Electrical Engineering, XLV [February 1926], 334-48), in which they relate acoustical energy to electrical energy, and describe what was later known as the "theory of matched impedance." In fact, they were describing the pre- and post- (record and playback) equalization, or pre-emphasis/de-emphasis that is still the manner in which records are cut and played today.
To ascertain some of the general characteristics of cylinders, I collected samples of every type of cylinder I could find from our archives, from collectors, and from other sources: a representative batch of brown waxes, Amberols, Blue Amberols, Concerts, Columbias and others. These were sent to the late Ed Catalano, chief chemist for the Gamma Omega Association. He reported that the surface deterioration of the cylinders was caused more by internal stress then by mold and mildew. Photomicrography was done on cylinder surfaces, and several samples were broken to enable photography of the various layers. A test washing of a moldy cylinder surface produced the results shown in Figure 1. Despite the frequent statements in the literature about Maplesons that the extreme surface noise is due to fungus attack, they do not in fact suffer from excessive fungus attack. The fact is that by 1937 Lionel Mapleson and his colleagues had played some of the cylinders to a physical point of no return.