Handbook for Sound Engineers

1596 Chapter 45

conventional 5.1 playback systems, while cinema
owners wishing to take advantage of the extra channel
can equip their theaters with an additional decoder unit
and power amplifiers. No additional loudspeakers are
usually required, only rewiring the existing banks of
surround loudspeakers, Fig. 45-5.

45.5 Surround Sound Comes Home

In 1982, recognizing the increasing popularity of watch-
ing VHS videotapes of theatrical movies in the
home—and that the extra, matrix-encoded channels on
Dolby Stereo movies were being transferred intact to
their stereo (two-track) VHS versions—Dolby intro-
duced the concept of surround sound in the home. It was
dubbed Dolby Surround to differentiate it from the film

process then still known as Dolby Stereo, and the term

is still used today to identify any program material with

stereo (two-track) soundtracks matrix-encoded for

four-channel surround playback at the viewer’s option.

Initially, Dolby developed a simple decoder circuit

that passively derived just the surround channel from

encoded VHS soundtracks, then licensed it to consumer

electronics manufacturers. Later, in 1987, they intro-

duced and began licensing a more sophisticated, true

four-channel decoder, called Dolby Surround Pro Logic,

with active steering and other features adapted from

their professional cinema sound processors.

Pro Logic decoding, which began to be featured

more and more in multichannel home playback prod-

ucts, heralded a new kind of home entertainment system,

the home theater. During the late 1980s and well into the

Figure 45-4. The 5.1-channel format was first adopted for digital surround sound in the cinema.

Left Surround

Screen

Left Center Right

Power

amplifiers

Sound

processor

Projector

Right Surround

LFE

Figure 45-5. Surround EX adds a third surround channel at the rear of the auditorium.

Left surround

Screen

Left Center Right

Power

amplifiers

Sound

Projector processor

LFE

Right surround

Rear surround