Specifications

E-4
(made all but obsolete by the stereo optical format), consistently higher fidelity,
and few of the drawbacks of magnetic formats.
Much of the new technology, including noise reduction and equalization, also is
applied to 70 mm magnetic releases (also originally designated as Dolby Stereo).
Although 70 mm release prints continue to be very expensive, Dolby
improvements brought a resurgence of interest in this “big” format for road shows
where the ultimate in picture and sound presentation is particularly likely to be
reflected in box office figures. There are six magnetic tracks on 70 mm film, two of
which carry low bass effects. Some 70 mm films also use a technique developed by
Dolby Laboratories to provide two separate surround channels in addition to the
left, center, right, and bass effects screen channels.
The Next Step: Dolby SR
In 1986, Dolby Laboratories introduced a new professional recording process
called Dolby SR (spectral recording). Like Dolby noise reduction, it is a mirror-
image, encode-decode system used both when a soundtrack is recorded and when it
is played back. It provides more than twice the noise reduction of Dolby A-type,
and, moreover, permits capturing loud sounds with wider frequency response and
lower distortion.
35 mm optical soundtracks treated with Dolby SR instead of Dolby A-type not only
sound superb in the more than 10,000 theaters equipped with special SR
processors, they also play back satisfactorily in any theater. As a result, most Dolby
SR titles are released single inventory. In fact, in theaters equipped with regular
A-type processors, the moderate compression that results helps prevent the louder
peaks on SR soundtracks from overloading the theater's sound system. This feature
further obviates the need for separate mixes and releases.
And Now - Dolby Digital
The newest film sound development from Dolby Laboratories puts a six-channel
digital optical soundtrack in addition to a four-channel SR analog track on the
same 35 mm prints. This Dolby Digital format is yet another significant step
forward in film sound, providing independent left, center, right, left surround, and
right surround channels, plus a sixth channel for bass effects.
In addition to multiple channels, the Dolby Digital track provides extraordinary
dynamic capability, wide frequency, range low distortion, and relative immunity to
wear and tear. The format has already proved its unique combination of high
quality, reliability, and practicality in theaters around the world. And because the
digital track is right on the film, the format has none of the drawbacks of separate
disc systems.