DOLBY PRO LOGIC
This is the consumer version of the system used in theatres to decode four channels of
sound from the film’s soundtrack and provides performance identical to that of theatrical
Dolby decoders. A sophisticated microprocessor control system in the SP MK II re-config-
ures the steering logic time constants to those of Pro Logic. The outstanding circuit topolo-
gy used within the SP MK II delivers Pro Logic decoding with superb sonic quality. Audio
signal delay settings range from 15 to 30 ms in 5 ms increments.
MONO ENHANCE:
This mode generates a synthesized surround field from a monaural
source. A pleasing, spatial effect can be derived from older music recordings, mono TV
broadcasts, or movies mixed in mono. The Panorama control is operative in Mono
Enhance.
BYPASS:
The Bypass mode allows the listener to electronically remove the SP MK II sur-
round processing circuits from the audio signal path. Only the left and right front speakers
and subwoofers remain functional. A single buffered gain stage with remote control of vol-
ume remains in the signal path.
LUCASFILM HOME THX CINEMA
Lucasfilm Home THX Cinema incorporates Dolby Pro Logic surround decoding along with
additional audio enhancements.
RE-EQUALIZATION:
Re-Equalization is necessary to compensate for the fact that the
soundtracks in films sound “bright” in a home environment. This results from a combina-
tion of the way we perceive sound in large auditoriums vs. small rooms and the theatre
equalization which has become standardized throughout the movie industry. The Re-
Equalization circuitry compensates precisely for these differences, restoring the sound to
its natural balance and minimizing listening fatigue by reducing harshness in the high fre-
quencies.
DE-CORRELATION:
The SP MK II incorporates a proprietary de-correlation circuit which
alters the phase/time relationships between surround channels to diffuse the perceived
sound. This eliminates the mono effect in the surround channels and helps to restore the
enveloping characteristic that is a system design goal.
TIMBRE-MATCHING:
The timbre or tonal balance of sound changes depending on
whether it comes from in front of you or from the sides. This has to do with the shape of the
outer ear. This is especially noticeable when the director pans a sound from the front
channels into the surround channel.
The character of the sound changes as the effect moves from the front to the surrounds,
even when the speakers are perfectly matched. This may reduce the realism of the effect.
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