5.1.2 Sound System (Motion Picture Presentation - theatrical projection)
Description
This article is from the rec.arts.movies.tech FAQ, by Scott E. Norwood snorwood@nyx.nyx.net with numerous contributions by others.
5.1.2 Sound System (Motion Picture Presentation - theatrical projection)
The sound system in a typical mid-size theater installation is capable
of handling from 200-400 watts of power for the front channels. In a
mono system, several loudspeakers are located behind the screen,
reproducing a single channel of sound. A Dolby Stereo (tm) or other
multichannel system involves at least three loudspeakers behind the
screen to reproduce the front channels, as well as several
loudspeakers along the side and rear walls of the auditorium to
reproduce the `surround' channel of sound. The soundtrack itself is
read from the film by a solar cell arrangement within a soundhead,
commonly a Simplex SH-1000 or similar.
Typical Multi-Track Dolby (tm) Stereo/Dolby (tm) Digital/DTS setup:
(This is the same setup used for Dolby (tm) Stereo, DTS (tm) , and
Dolby (tm) Digital setups, although the digital systems have separate
L and R surround channels, as well as a channel for a subwoofer [which
is located behind the screen]. Complete SDDS systems and 70mm also
have Left Center [LC] and Right Center [RC] loudspeakers, not
indicated here)
Left Stereo (L) -- behind left side of screen
Right Stereo (R) -- behind right side of screen
Center/Dialogue (C) -- behind center of screen
Surround (S) -- in rear of auditorium (separate L/R in digital)
Subwoofer (sub) -- behind screen (separate channel for digital)
/----------------------------------------------------------\
| * L * * C * * R * |
| * spkr * (sub) * spkr * * spkr * |
| ------------------- screen ------------------- |
| |
| (front of auditorium) |
| |
| UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU |
| UUUUUUU UUUUUUU audience UUUUUUU UUUUUUU |
| UUUUUUU UUUUU seating area UUUUU UUUUUUU |
| UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU |
| UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU |
\ \
/ /
\ \
|* S * UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU * S *|
|*spkr* UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU *spkr*|
| UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU |
| UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU |
|* S * UUUUUUU UUUUUUUUUUUUUUUUUUUUUUUU UUUUUUU * S *|
|*spkr* *spkr*|
| * S * * S * |
| *spkr* (rear of auditorium) *spkr* |
\----------------------------------------------------------/
Digital sound systems use similar loudspeaker arrangements as Dolby
Stereo (tm) setups, possibly with additional loudspeakers to support
SDDS (tm) eight-channel mixes. The sound is read by specialized
readers placed between the reels/platters and the projector head; this
contrasts with the placement of the analog soundhead, which is located
between the projector head and the take-up reel/platter.
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