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THX, Home THX, Re-Equalization, Timbre Matching, Adaptive Decorrelation, Advanced Speaker Array and THX Ultra are trademarks of
THX Ltd.
[6] THX Surround EX
In 1999, a new surround system was launched simultaneously with the release of the movie “Star Wars Episode I”. “Dolby Digital Surround
EX” is a new movie sound track that greatly enhances the sense of spatial expression and the positioning of the surround channel sound. The
result is 360 degrees of movement and moving sound effects that seem to pass right over the listener's head.
This system was developed jointly by THX and Dolby Laboratories, fusing THX’s idea of improving spatial expression and achieving a uniform
360 degree sound positioning with Dolby Laboratories' matrix encoding technology. Emphasis was placed on compatibility with the existing
system Dolby Digital 5.1-channel, and the new “surround back (SB) channel” was added to achieve improvements over the conventional 5.1-
channel system in terms of the positioning of the sound at the rear, the acoustic image of sound moving from the two sides to the back as
well as sound moving from the front to the center rear with the multi surround speaker systems used in movie theaters, thereby enabling
various types of surround sound.
The surround back channel signal is a matrix-encoded signal inserted into both the Dolby Digital SL (surround left) and SR (surround right)
channels. Upon playback, the signals are decoded by a high precision digital matrix decoder within the Dolby Digital decoder into the SL, SR
and SB channels and output as 6.1 channels of signals. With the AVR-5805, the signals further undergo Home THX Cinema processing to
achieve a THX Surround EX system.
Even without the proper environment for playing the SB channel, Dolby Digital Surround EX signals are 100% compatible with existing 5.1-
channel playback systems, so they can be played as such. In this case, the SB channel signal is produced as a monaural signal from both the
SL and SR channels, so none of the signal components are missing. The effects specific to THX Surround EX (the sense of spatial expression
and the positioning of the sound), however, are the same as with conventional 5.1-channel surround systems.
THX and Ultra 2 are trademarks or registered trademarks of THX Ltd. Surround EX is a jointly developed technology of THX and Dolby
Laboratories, Inc. and is a trademark of Dolby Laboratories, Inc. Used under authorization. All rights reserved.
THX Ultra2 Cinema
THX Ultra2 Cinema mode plays 5.1 movies using all 8 speakers giving you the best possible movie watching experience. In this mode, new
THX processing blends the side surround speakers and back surround speakers providing the optimal mix of ambient and directional surround
sounds.
DTS-ES (Matrix and 6.1 Discrete) and Dolby Digital Surround EX encoded soundtracks will be automatically detected in Ultra2 Cinema mode
if the appropriate flag has been encoded.
Some Dolby Digital Surround EX soundtracks are missing the digital flag that allows automatic switching. If you know that the movie that you
are watching is encoded in Surround EX, you can manually select the THX Surround EX playback mode, otherwise THX Ultra2 Cinema mode
will apply processing to provide optimum replay.
THX Music Mode
For the replay of 5.1 multi-channel music the THX MusicMode should be selected. In this mode new THX processing is applied to the surround
channels of all 5.1 encoded music sources such as DTS and Dolby Digital to provide a wide stable rear soundstage.
THX Games Mode
•THX Games Mode operating on 5.1 game material
Game Audio is mixed and monitored in a different environment than that of music and movies. The interactive nature of the audio requires
a playback system which can provide 360 degree panning while preserving the ambient nature of background sound elements. When
playing back 5.1 games, the THX Games Mode should be selected. Suitable sources are DTS 5.1 and Dolby Digital 5.1 game sources.
•THX Games Mode operating on 2.0 game material
2.0 game audio requires a different operation than that of multi channel game sources. When playing back 2.0 games, the THX Games
Mode button should be selected. Suitable sources are 2.0 game audio tracks such as Stereo analog, 2.0 PCM, or 2.0 Dolby Digital and 2.0
DTS.
Advanced Speaker Array
ASA processing offers maximum effect when two surround back speakers are used and the speakers are placed near each other. This
technology is used for Ultra2 Cinema, THX Music Mode, THX Games mode and THX Surround EX.
Boundary Gain Compensation
When using a THX Ultra2 compatible subwoofer or a subwoofer with ultra-low frequency playback capabilities (with a frequency response
extending to approximately 20 Hz), the low frequency band may rise and the sound may seem booming. This technology compensates the
gain and makes the audible level flat.
