ABSTRACT
The method of recording in which all energy comes from the sound waves themselves; it was used from the earliest days of Edison and Berliner until the onset of electrical recording in 1925. Sounds to be recorded were sung, played, or spoken into a horn, which activated a diaphragm attached to a stylus. The stylus transferred the vibration patterns to the surface of a cylinder or a disc. To concentrate this acoustic energy sufficiently for the stylus to etch a usable pattern it was necessary for singers and performers to direct their vibrations into a large collecting horn; this requirement favored strong sound producers, and worked against inclusion of weaker vessels like string instruments. Great ingenuity was applied in the acoustic recording studio to overcome these inherent obstacles. Horns were varied in diameter for different sound sources; they were wrapped with tapes to counter their own resonance; they might be used in clusters, running to a single tube
which moved the diaphragm. For a few recordings, Edison used one brass recording horn 125 feet long and five feet in diameter at the bell. Different thicknesses of diaphragm were used depending on the volume of sound being handled-thinner for weak sounds, thicker for heavy sounds.
