Proceed PDSD - Manual (Page 62)

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When in doubt as to whether THX cinema processing should be included, listen
for a natural presentation of the treble. Films mixed for theatrical release exhibit
an elevated treble region when played back on a home system with flat response.
The
THX cinema mode will correct this. Conversely, surround-encoded programs
without this high frequency emphasis might sound dull or lacking in detail when
(incorrectly) played in the
THX cinema mode.
dolby pro logic surround Some two-channel program material does not conform to film industry standards,
although it may still be Dolby Surround encoded so it can decode to four chan-
nels. Music videos on MTV, for instance, are often Dolby Surround encoded, but
have soundtracks which are produced in non-film studios. In fact, a growing
number of music CDs are mastered with surround sound. These sources and
others which have surround encoding but which are unlikely to have been mixed
or remixed in industry-standard production facilities should use the
pro logic
mode to avoid compensation where none is indicated.
stereo surround The stereo surround mode has been carefully designed to extract real ambience
from your recordings rather than synthesizing something artificial that might be
quite alien to the music itself. The ambient cues found in the program material
are then used to provide appropriate information for the center and rear speakers.
The front Left and Right speakers are left unaffected by this mode, allowing you
to hear unadulterated stereo imaging with the addition of a genuine sense of hall
ambience.
Since this mode is based on the recordings themselves, it is normal to hear some
variation in the degree of the effect. Extremely “dry” recordings which lack any
significant ambience may not sound significantly different than when in
surround
off mode (e.g., two-channel stereo). You may find that increasing the level of the
rear speakers is necessary in order to bring what little ambience is in a “dry” re-
cording up to a more enjoyable level.
mono surround The mono surround mode can provide a sense of spaciousness and size to
monophonic program material such as some historical recordings and movie clas-
sics such as Casablanca or The Wizard of Oz. The
mono surround mode makes
no effort to “electronically reprocess to simulate stereo” (a process which almost
always causes more harm than good). Instead, it uses sophisticated steering tech-
niques to create a sense of space in what would otherwise be a largely dimen-
sionless soundfield. It is particularly helpful when viewing mono program mate-
rial on a big screen, where a tiny mono image would simply sound wrong in
contrast to the big picture.
surround off The surround off mode is intended for music reproduction without any form of
surround enhancement. In this mode, the Left and Right speakers are active along
with the subwoofer(s), and reproduce the input without any processing other
than the electronic crossover needed for the subs.
mono The mono mode sums the incoming Left and Right signals. The result is sent to
the center channel speaker, as well as the subwoofer(s). This mode is especially
useful for older, classic films or historical recordings which have noisy mono
soundtracks. Since much of the noise is likely to be random in phase, significant
noise cancellation can often be achieved by playing these mono sources in a true
mono mode.