Lexicon DC-1 Supplementary Manual page 21

DC-1 Theory
and Design
TV Viewing
18
THX CINEMA combines Dolby Pro Logic decoding and the spectral en-
hancements of the LucasArts Home THX Cinema system. In this effect, the
side and rear speakers are driven in parallel as in Pro Logic, but there is a
decorrelation effect between the left and right side channels. A Stereo
Surround parameter in the DC-1 provides further enhancement, making
the effect similar to Logic 7, but with no differentiation between the sides
and rears.
LOGIC 7 takes decoding further with the introduction of true seven channel
decoding using a stereo surround process. Steered signals are panned to the
front, side and rear speakers so that surround information follows the visual
movement on-screen. Ambient surround information, such as stereo music
in the soundtrack, is reproduced at full bandwidth and in stereo in the rear
channels. Sound effects which pan to the left or right of the listener are
reproduced with full realism.
DOLBY DIGITAL decodes six discrete channels of digital information from
Dolby Digital soundtracks. Improvements to film sound reproduction
include improved dynamic range, superior channel separation, a dedicated
subwoofer channel, and discrete sound effects.
THX 5.1 provides Home THX Cinema enhancements for film soundtracks
recorded in the Dolby Digital format.
5.1 LOGIC 7 optimizes Dolby Digital sound when played in systems with
both side and rear speakers. The timing and equalization of left surround
and right surround information is different for side and rear channels to
provide a more theatrical presentation of Dolby Digital film soundtracks.
5.1 MUSIC enhances playback of Dolby Digital music recordings or Dolby
Digital film soundtracks with strong musical content.
5.1 TWO CHANNEL mixes Dolby Digital 5.1 information for two-channel
playback. These soundtracks can be recorded onto two-channel formats for
later playback through a surround effect such as Logic 7, or they can be
played back through left and right front speakers.
Television sound playback presents a challenge simply because of the wide
variety of recording and processing techniques used in program produc-
tion and transmission. Programs and commercials are recorded in mono,
stereo, and surround sound, then subjected to compressors, erratic stereo
synthesizers, sleepy production interns, and other electronic tortures. Often
all of this can be experienced on one channel within five minutes.
The TV Matrix effect makes use of directional steering to enhance dialog in
the center channel and remove it from the left and right channels, while
maintaining as much stereo separation as possible. In addition, it contains
several interesting variable parameters. In the preset version of TV Matrix
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