User:IOMarshall/sandbox

In 1977, Dolby debuted the 70mm "Baby Boom" format and used the same 70mm format as Todd-AO with a reconfiguration of it's original six-track sound. The new setup utilized speakers leftover from old 70mm Todd-AO engagements. There were three screen channels, one surround channel and two dedicated boom channels that utilized frequencies below 200 Hz. Encoding Dolby A-type NR (Noise Reduction) on prints meant that each of the six magnetic tracks could carry more level with less distortion.

Warner Bros. "Superman" (1978) was the first film to use the 70mm "Split Surround" as a Beta project. The surround was split into left and right. The left/right high frequencies were recorded left-center/right-center, while sharing these tracks with the booms, which were recorded at lower frequencies. A new filter then split the bass from the treble outputting stereo surrounds, plus the boom tracks on channels 2 and 4. The surrounds were limited @ 500 Hz and the booms @ 200Hz. Speakers were also reconfigured with moving two of the mid-centers from behind the screen to the rear of the cinema. Today, this configuration is known as Dolby 5.1 Surround.

"Apocalypse Now" (1979) was the first film to officially make use of this new 70mm Split Surround. And required theaters that had 70mm capability to purchase a then estimated $4000.00 upgrade to their Dolby CP-100 Sound Processors. The upgrade involved replacing their existing Surround Adapter with the newly developed Dolby SA-5. This new adapter did the splitting and filtering of the new surround track configuration. Warner Bros. MegaSound was developed to be the bass extension to this new 70mm Split Surround system.

MegaSound made it's addition to this system by way of subharmonic synthesis using a customized and pre-configured rack-mount processor. Also additional BGW or Cerwin-Vega power-amps and Universal-style Cerwin-Vega E horns or the later Cerwin-Vega L36 JE folded horns as the speaker-array were used. The extra power and speakers in some installations were left-over from MCA/Universal's previous Sensurround presentations. The Altec A4 could also be used as an speaker alternative. The entire concept to some degree was to build on what was already available in many 70mm theaters. However, limited to only those that had made the SA-5 purchase or could upgrade to the later Dolby CP-200 released in May 1980 (which had the SA-5 capabilities built-in) and was willing to spend even more on a bass enhancement.

Only 70mm Six-Track Dolby A-type NR magnetic prints could be used for MegaSound, as it synthesized (using compression and digital delay) the harmonics of the incoming boom tracks' low-frequency signals to synthesize incredible deep-bass using a relatively small array of subs and horns. Also with lesser risk of overloading amps or damaging these smaller speakers. The MegaSound processing algorithms were triggered by low-frequency bass below 40Hz from a DBX-type MegaSound encoded soundtrack. The bass generation synthesis had a custom cut-off fail-safe @ 16Hz to prevent risk of structural damage to the presentation venue.

MegaSound processing was provided by subharmonic processors such as the Eventide Clockwork Inc. Harmonizer or the Aphex Aural Exciter. These units were specially modified to work in the infrasonic range and bore the MegaSound logo on their casing. Since MegaSound was capable of operating into the infrasonic range with a max-low of 16Hz @ 120db, it's bass extension was really unlike or incomparable with any modern sound system.

Alleged Presentations
MegaSound was allegedly beta tested using the 1979 re-release of "The Exorcist" (1973) 70mm conversion. MegaSound had also been advertised with 1982 premiere engagements of "Blade Runner" in Manhattan at the Criterion.