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CENTER SURROUND 3X
CONCEPTS
Digital Audio tracks are discrete, that is, each track
can contain information that is totally separate from
the information on other tracks. Since they are dis-
crete tracks, it is possible to apply a matrix encod-
ing process to any two of these tracks, just as it is
done for optical stereo prints. Therefore, multiple
channels of audio can be encoded into the two se-
lected tracks. The Digital Left Surround and Digital
Right Surround tracks have been selected to receive
the matrix encoded signals. The new digital prints
have an additional surround channel encoded into
the Left Surround and Right Surround tracks. While
Rear Wall Speakers
digital recording is a fine storage media, at some
point the digital signals have to be converted back
to analog to be heard. A properly designed matrix
is not going to significantly affect the quality of the
resulting analog signals.
The Center Surround 3X processor is a multi-chan-
nel matrix decoder that extracts the multiple chan-
nels from the Digital Left Surround and Digital Right
Surround tracks and sends these signals on to the
appropriate power amplifiers and speakers. By sepa-
rating the surround speakers on the back wall of
the cinema into a separate group, these speakers
can deliver sounds from the rear wall channel which
are separate from the left wall and right wall chan-
nels.
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This concept can be extended even further because
the matrix can decode additional channels from
the original two channels. For example, speakers
could be placed overhead so that passover effects
Off Stage Speakers
Overhead Speakers
Rear Wall Speakers
become much more realistic. These additional chan-
nels would have to be encoded on the soundtracks.
The overhead speakers, if used, do not have to be
as high a quality as the surround speakers. In fact,
if the overhead speakers high frequency response
is limited in comparison to the stage and surround
speakers, then the perception will be that the speak-
ers are located higher up than they really are since
high frequencies are normally attenuated more and
more as the distance increases. This gives the illu-
sion of distance which can contribute to the over-
head effect.
Alternatively, mid-size full range off-stage effects
speakers could be placed on the side walls, angled
into the audience, between the screen and the sur-
rounds so that voices or effects could be placed
offstage. This all leads to a greater sense of reality
in the audio presentation. These off-stage channels
would have to be encoded on the soundtracks.
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