User`s manual

Dolby
®
CP650 Digital Cinema Processor User’s Manual The Evolution of Dolby Film Sound
B-2
speakers. The result was to ignore the improved high-frequency response of the
newer, better units.
To forestall compatibility problems, in the late 1930s a de facto standardization set in,
the cinema playback response that today is called the Academy characteristic. Cinema
owners knew what to expect from the films, and therefore what equipment to install.
Directors and sound recordists knew what to expect from cinema sound systems, and
thus what kind of soundtracks to prepare. The result was a system of sound recording
and playback that made it possible for just about any film to sound acceptable in any
cinema in the world. The problem now was that the system lacked the flexibility to
incorporate improvements beyond the limitations that existed in the 1930s.
Magnetic Striping and Multichannel Sound
In the early 1950s, as the film industry sought to woo viewers away from their
fascinating new television sets, a new method of putting sound on film was
introduced. After the picture was printed, narrow stripes of iron oxide material
(similar to the coating on magnetic recording tape) were applied to the release print.
The sound was then recorded on the magnetic stripes in real time. In the cinema,
magnetic prints would be played back on projectors equipped with magnetic heads
similar to those on a tape recorder, mounted in a special soundhead assembly called a
penthouse.
Magnetic sound was a significant step forward, and at its best provided much-
improved fidelity over the conventional optical soundtrack. It also enabled the first
multichannel sound reproduction, dubbed “stereophonic sound,” ever heard by the
public. The voice of an actor appearing to the left, center, or right of the picture could
be heard coming from speakers located at the left, center, or right of the new wide
screens also being introduced at this time. Music took on a new dimension of realism,
and special sound effects could emanate from the rear or sides of the cinema. The two
main magnetic systems adopted were the four-track 35 mm CinemaScope system,
introduced with The Robe, and the six-track 70 mm Todd-AO system, first used for
Oklahoma!
Magnetic Falls into Disuse
Magnetic sound was widely adopted in the 1950s. By the 1970s, however, when the
film industry experienced an overall decline, the expense of magnetic release prints,
their comparatively short life compared to optical prints, and the high cost of
maintaining the playback equipment led to a massive reduction in the number of
magnetic releases and cinemas capable of playing them. Magnetic sound came to be
reserved for only a handful of first-run engagements of major releases each year.
By the mid-1970s, then, moviegoers were again hearing low-fidelity, mono optical
releases most of the time, with only an occasional multitrack stereo magnetic release.
Ironically, just as the industry was reverting to mono optical, more and more
moviegoers were enjoying better sound at home over superior hi-fi stereo systems.