the Rise of the Dolby Empire

Dolby Laboratories, founded by Ray M. Dolby, developed in 1965 a noise reduction for professional use, Dolby A(-Type). The first film to use Dolby's noise reduction was "A Clockwork Orange" in 1971. All magnetic recordings and mixes were treated with Dolby A; the final release however, was in academic mono.

In 1972 "A Quiet Revolution" was released, the first film with a release print with A-Type. It was used to show the advantages of noise reduction. The same year Dolby developed their first decoder for optical soundtracks treated with A-Type. In 1974 Dolby presented their first movie sound format: an optical mono soundtrack treated with Dolby A. It was first used on "Callan". Also in 1974 Dolby, Eastman-Kodak and RCV released a stereo (2 channel) (dual bilateral) variable area soundtrack.

A real revolution came when they developed Dolby Stereo. On a 35mm film a dual bilateral optical track was placed. This track was treated with Dolby A but more important it contained encoded information for 4 channels. The result was that now 4 channels were available: left, center, right and surround. (see "How does Dolby's matrixed sound work?") The multichannel soundtrack was placed on the same place as the 'Academic' or Dolby A track and made Dolby Stereo compatible with all older mono playback equipment.
Dolby Stereo was first demonstrated in 1974 during a convention of SMPTE (Society of Motion Picture and Television Engineers). Specially re-mixed sections of "Stardust" were used to compare the new optical system with the existing 35mm magnetic system. The first film with a Dolby Stereo soundtrack was "Lisztomania" in 1975 but only the 3 screen channels were used. Although "A Star Is Born" (1976) was the first to feature Dolby Stereo with encoded surround effects, it was the 1977 release of "Star Wars" and its enormous succes that made Dolby Stereo famous, almost overnight.

Dolby realised that magnetic sound still provided a higher fidelity than optical sound, even if it was treated with A-type noise reduction. So in the same year Dolby Stereo and "Star Wars" conquered the world, Dolby presented their own variation of the magnetic 6-track system of Todd-AO. The six channels of Dolby Stereo 70MM Six Track were left, center, right, surround and 2 low-frequency-only (below 200Hz) channels. The 2 bass channels gave this format its nickname: 'Baby Boom'. Because screens had become smaller there was no need anymore for 5 channels behind the screen but films such as "Star Wars" and "Close Encounters Of The Third Kind" had demonstrated that seperate bass channels were welcome.

In the late 1970s Dolby released an important refinement of its 70MM magnetic format. Unlike 'Baby Boom', the new format had only one low-frequency-only channel. The channel that now became available, was used as a second surround channel, thus creating stereo surrounds. The format had a left, center, right and a bass channel behind the screen and a left and right surround channel in the auditorium, the same setup up as most digital formats nowadays (see the Digital Revolution.
The 'Stereo Surround' format was backwards compatible with the 'Baby Boom' format. The 2 surround channels of 'Stereo Surround' replaced the 2 bass channels; 'Baby Boom's mono surround channel became the bass channel of 'Stereo Surround'. By limiting the bass sounds to under 200 Hz and surround sounds to frequencies higher than 500 Hz it was possible to include the 2 mixes on a single 70mm print. A 'Stereo Surround' setup used only the high-frequency sounds of the 2 surround/bass channels to give split surrounds and ignored the lower frequencies of these channels. With the bass/surround channel the low frequencies were fed to the subwoofer. For 'Baby Boom' it's the other way around.
It was tested on "Superman" (1978) but it was first used with "Apocalyps Now" in 1979 .

Dolby presented in 1986 a new recording system: Dolby SR (Spectral Recording). Dolby SR had twice as much noise reduction as Dolby A did and provided a wider dynamic range, higher frequency response and lower distortion. "Innerspace" and "Robocop", both released in 1987, were the first movies to be presented in Dolby Stereo SR, an improved version of Dolby Stereo with Dolby SR instead of Dolby A. The 35mm optical soundtracks treated with Spectral Recording provided not only better sound in theaters equiped with new SR-processors but in all cinemas. Dolby Stereo SR used the same setup as regular Dolby Stereo, so it was completly compatible with existing Dolby equipment.