“threads per inch”) was 150, a much finer grooving than that on lateral discs, Edison’s 10-inch discs played considerably longer than Victor’s or Columbia’s - up to nearly five minutes per side. As the Edison groove pitch (or “TPI”, i.e.
Standard lateral discs will have a more constant depth, but the sides of the groove are scalloped. The grooves on an Edison Disc are smooth on the sides and have a variable depth. The Victor (or similar) diaphragm is located at a right angles to the surface of the disc such that the diaphragm is more or less parallel to the groove. An Edison Disc Phonograph is distinguished by the diaphragm of the reproducer being located parallel to the disc surface. Victor and most other disc record companies used side to side or lateral motion of the stylus in the record groove, whereas in the Edison system the movement was up and down or vertical (also known as “hill-and-dale” motion), as in a cylinder record. Note the thickness of each record.Įdison had previously concentrated on producing phonograph cylinders but decided to get into the disc market due to the increasing market share of disc sound recordings, especially the discs of companies such as Victor Talking Machine Company (the format of which would evolve into “78 records”).
