In 1940, Walt Disney's Fantasia was the first film to be released in a multichannel format called Fantasound. Some important innovations are as follows:
Conductor Leopold
Stokowski and Walt Disney collaborated on the production and concept
of this innovative movie. Fantasia is a feature-length film that choreographs
animation
to music. Stotowski wasted to bring mutichannel sound in Fantasia. Stokowski's
involvement with this new technology dates back to the Thirties, when he
began research with Bell Telephone Lab's early "Auditory Perspective"
experiments on stereophonic sound. Bell's most famous demonstration came
when the Philadelphia Orchestra, conducted by Stokowski, was transmitted
over three telephone lines to an astonished audience in Washington's Constitutional
Hall.
Eight optical recorders were employed to record the Philadelphia Orchestra conducted by Stokowski. Using multiple optical recorders allowed sections of the orchestra to be handled separately during mixdown, a new concept at the time. Six channels were devoted to individual orchestral sections, one to a distant mic, and another to a balanced mix. A ninth track was later added to give animators a guide for timing. Recording began on April 7, 1939, and consumed a half million feet of sound film during 42 days of recording. Because of the multitrack nature of the recording, overdubs of individual sections of the orchestra could be performed easily.
Supervising acoustician for the production, John Volkmann worked out all of the mic set ups for the recording. To do this, Volkmann worked with stage layouts, directional plots of the RCA velocity mics, directional plots of the orchestral sections, and reverberation time to pick out the precise mic placement desired. Volkmann recording setup documentation included mic positions and electrical paths including details of gain and frequency characteristics. A total of 44 RCA velocity mics were used. An operator would mute mics not being used to minimize noise and leakage.
A special system was devised for playback of Fantasia called Fantasound. The Fantasound system employed two projectors. The first one projected the picture and had a mono optical mix of the entire soundtrack. This mono mix was used as a backup system in case of failure of the main soundtrack. A technique that is used in all of today's successful digital sound systems. The second projector was played in synchronization to the projector with the picture information. This second projector employed four mono optical sound tracks as follows: 1. control track; 2. screen left; 3. screen right; and 4. screen center. This three channel speaker array was similar to the original stereo setup proposed by Bell Labs in the Thirties. In addition to the screen left, right, and center, there was house left, right, and center channels. These channels were derived from the screen left and right channels and were the equivalent of surround channels. The control track had various amplitude and frequency tones that drove Voltage Gain Amplifiers (VGAs).
The original orchestral recording was recorded as close to peak modulation as possible to increase signal-to-noise-ratio. The control track could then be utilized during playback to later restore the dynamics to where Stotowski felt they should be. This control track system was known as the tone-operated gain-adjusting device (Togad). This unique system controlled the levels of each of the main soundtracks through the VGAs with a dynamic range of 50 dB. The superposed frequencies of 250, 630 and 1600 Hz each varied in level. The control track is filtered and the VGA can be biased to a 8:5 ratio in cases where the theater ambient noise may be excessive. Both the VGA and the tone rectifier circuits employed a time constant of 15 ms. Disney engineers felt that if a future Fantasound format was ever developed, it should include level-dependent equalization.
Disney's chief engineer, William Garity had the challenge of trying to simulate sound moving back and fourth across the screen. He determined that fading between two speakers might be able to create this illusion. A special 3-circuit differential junction network was created to accomplish the task. Thus Disney could use it to mix down to a three track master. They called this device "The Panpot". Later a two channel Panpot was created to vary the ratio between close and reverberant sound while maintaining constant level. Mixdown required six mixers to control the various Panpot in real time. The mix was performed much like a modern film scoring session with Stokowski conducting pans and level changes. Stokowski had marked all of these level and pan changes measure by measure in his musical score. A special three-color oscilloscope was employed to monitor the levels of the mix. Each color of the oscilloscope represented a different channel of the mix implementing translucent masks. At the time, there were no VU meters which we would now expect.
When Fantasia debuted in New York's Broadway Theater on November 13, 1940, the surround mix the audience heard was mixed live by a sound mixer operating under Stokowski's supervision. Because of production factors, the true Fantasound format debuted later. During this screening, surround channels were only utilized during the last piece, "Ave Maria". For the first time, an audience was enveloped with surround information.
Only two Fantasound systems were sold to two theaters: New York's Broadway Theater and the Carthay Circle Theater in Los Angeles. These installations cost $85,000 and included 54 speakers placed throughout the auditorium. Because of this high cost, Disney devised a system known as the "Fantasia Road Shows". Eight of these scaled back versions of Fantasound were produced. They were $45,000 and weighed 15,000 pounds each. They toured a total 14 theaters and each one filled up half of one freight car during shipment. Because of the cost, the roadshow did not include the house (surround) speakers. The road show version used a separate mix. Instead of having the tracks be screen left, right, and center, they were orchestra, choruses, and soloists respectively.
As the film toured the country, some refinements were made in the Fantasound Process. It was determined that a series of edge notches on the film could be used to control a series of relays. These relays could be used to turn various loudspeakers off and on to reduce noise as well as more sophisticated dynamic automation. In 1942, the film was re-released with just a mono soundtrack and 43 minutes cut out of it. It was not until 1956 that Disney restored Fantasia to its original length and a four track magnetic format soundtrack. This 1956 version, although in stereo, contained no surround information. In 1982, Fantasia was re-released yet again. This time it was a completely new soundtrack. Engineer Shawn Murphy recorded a new digital recording of the original music using a Soundstream four track digital recorder using a sampling frequency of 50 kHz. Although this recording had better fidelity than was possible in the Forties, many consider it inferior. Fantasia fanatics point to the fact that the original recording has a much better performance. In addition, the panning was much more radical in the original. There is a certain nostalgia connected with the original. Today, many consider the original panning information very ping pongy. However, we can forgive them for this for bringing the Panpot into existence in the first place.
In 1990, Disney decided to re-release the film again. This time the movie had a restored picture and soundtrack. A copy of the original master did replace the 1982 digital recording. Because the optical master disappeared, the re-release used the 1956 magnetic master. The 1956 magnetic master was made from the original Fantasound system. This was accomplished by transferring the original mix to RCA's studios over Class A telephone lines. Disney's Terry Porter spent months studying the original drawings, documentation, manuals, and notes from the original production. His first step was to clean up as much noise, hum, and distortion. Porter had to clean up over 3,000 pops from the 1956 magnetic master. The transfer from the telephone lines left some artifacts that also had to be fixed. Porter then did a Dolby Stereo SR mix of the cleaned up tracks. Because of complicated phase relationships in the 1956 magnetic master, delay lines were employed to induce proper steering of the channels.
For
the 1990 re-release, Disney decided to develop Fantasound '90. This format
exhibited at the Cinerama Dome only in Los Angeles. It followed the original
Fantasound set up, except the mix was on 6-channel magnetic. There was
also a standard 70mm Dolby Six Track Stereo Surround format released to
other theaters. Because of the 5.1 nature of this particular 70mm format,
this could be used to make a DVD master. For the 1990 video release, conventional
Dolby Surround was employed.
Because of the work of Disney, RCA, and Bell Labs, Fantasia and Fantasound were possible. Fantasound led to a variety of magnetic techniques and eventually to Dolby Stereo. The new Digital film techniques we have today use ideas first pioneered in Fantasound.
For further reading
Blake, Larry. "Re-Recording and Post Production for Disney's Fantasia." Film Sound Today: An Anthology of Articles from Recording Engineer/Producer. Ed. Mel Lambert. Hollywood: Reveille Press, 1984. 19-24.
Blake, Larry. "Mixing Dolby Stereo Film Sound." Film Sound Today: An Anthology of Articles from Recording Engineer/Producer. Ed. Mel Lambert. Hollywood: Reveille Press, 1984. 1-10
Klapholz, Jesse. "Fantasia: Innovations in Sound." Journal of The Audio Engineering Society, Vol. 39, No. 1/2 (1991): 66-70.
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