International projectionist (Jan 1941-Dec 1942)

'Fantasound': a Technologic Epoch THE art of sound-picture reproduction is about 15 years old. While an engineer familiar with the complications of sound reproduction may be amazed at the tens of thousands of trouble-free performances given daily, the public takes our efforts for granted and sees nothing remarkable about it. Therefore, we must take large steps forward, rather than small ones, if we are to inveigle the public away from soflball games, bowling alleys, nightspots, or rapidly improving radio reproduction. The public has to hear the difference and then be thrilled by it, if our efforts toward the improvement of sound-picture quality are to be reflected at the box-office. Improvements perceptible only through direct A-B comparisons have little box-office value. While dialog is intelligible and music is satisfactory, no one can claim that we have even approached perfect simulation of concert-hall or live entertainment. It might be emphasized that perfect simulation of live entertainment is not our objective. Motion picture entertainment can evolve far beyond the inherent limitations of live entertainment. Reproduction Deficiencies Before discussing the operation of the Fantasound equipment, some deficiencies of conventional sound-picture reproduction may be summarized: (a) Limited Volume Range. — The limited volume range of conventional recordings is I J. Soc. Mot. Pict. Eng., August, 1941. By WILLIAM E. GARITY and J. N. A. HAWKINS MEMBERS, TECHNICAL STAFF, WALT DISNEY PRODUCTIONS Here is the thrilling story of that marvelous technical achievement of the multiple-speaker system known as "Fantasound," currently used for reproducing Walt Disney's "Fantasia," now established after 48 weeks consecutive showing on Broadway as the all-time, all-champ sound motion picture. Technical preparation for this epic production included the exploration on paper of several hundred different equipment combinations, which subsequently were translated into ten different systems before the final form was decided upon. The production of "Fantasia," excluding release prints, required the use of five million feet of film! In the appended article are discussed first some of the deficiencies of conventional sound-picture reproduction, and then follows a complete history of the "Fantasound" development. In addition are described in considerable detail the various important elements of the system. No technician will fail to be thrilled by this exposition of the planning and execution of one of the greatest technical achievements in the history of the film art. reasonably satisfactory for the reproduction of ordinary dialog and incidental music, under average theatre conditions. However, symphonic music and dramatic effects are noticeably impaired by excessive groundnoise and amplitude distortion. (b) Point-Source of Sound. — A pointsource of sound has certain advantages for monaural dialog reproduction with action confined to the center of the screen, but music and effects suffer from a form of acoustic phase distortion that is absent when the sound comes from a broad source. (c) Fixed Localization of the SoundSource at Screen Center. — The limitations of single-channel dialog have forced the development of a camera and cutting technic built around action at the center of the screen, or more strictly, the center of the conventional high-frequency horn. A threechannel system, allowing localization away from screen center, removes this single-channel limitation, and this increases the flexibility of the sound medium. (d) Fixed Source of Sound. — In live entertainment practically all sound-sources are fixed in space. Any movements that occur, do so slowly. It has been found that by artificially causing the source of sound to move rapidly in space the result can be highly dramatic and desirable. It is felt that Fantasound provides a desirable alternative to the four major deficiencies just described. There have been other attempts to provide increased volume range and a broad sound-source. It appears that three separate program channels are an essential part of any solution to these sound problems. The matter of maximum usable loudness in the theatre is closely related to the number of separate program channels used. Three channels sound louder than one channel of three times the power-han > > Tone Amp Z50~ TR 630TR l6O0~ TR FIG. 1. Simplified block diagram of Fantasound reproducer FIG. 2. Circuit diagram of the variable-gain amplifier 16 INTERNATIONAL PROJECTIONIST