The Edison Disc format is similar to the Victrola Disc Record format with one exception. The modulation inside the groove is normal to the Disc rather than from side to side on a Victrola. And Edision Disc Player is noted by the diaphram of the reproducer being located parallel to the Disc surface. The Victrola diaphram is located at right angles to the surface of the disc. The grooves on an Edison Disc are smooth on the sides, and have a variable depth. A Victrola Disc will have a more constant depth, but the sides of the groove are scalloped. Since the turntables and Disc sizes were the same, some Disc players were equipted with new pickup to be able to play the Victrola Discs. The RCA Victrola system did a poor job of playing Edison Discs, and the Edison system did a poor job of playing the Victrola discs. The Edison system become most popular for wax cylinder recorders. The Victrola system eventually won out for Music recordings. Later the Edison Disc Recording system was revisited when Stereo recordings on Discs were made. Because the Edison Disc Recording was perpendicular to that of the Victrola, cross modulation was minimized when one channel was recorded on one axis, and the other channel on the perpendicular axis. The variable depth and width of the groove was difficult to maintain, and typically the Edison Disc Depth modulation tended to wear out more quickly than the side to side modulation of the Victrola Disc recording system. The final solution was to rotate the two perpendicular modulations 45 degrees so that instead of left-right, and up-down, they are modulated 45 degrees normal to the surface of the Disc. The Axis is now an X instead of +. This allowed the wear to be more evenly distributed, and was still able to be played with various size needles.