Denon AVR-4806CI User Manual download pdf (Page 153)

153

Additional Information

[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-4806CI, 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 Ultra2 are trademarks of THX Ltd. THX may be

Surround EX is a trademark of Dolby Laboratories. Used

with permission.

Audyssey MultEQ XT

There are several factors that can degrade the sound from

even the best loudspeakers in a listening room. One of the

most important is the interaction of sound from the

loudspeakers with large surfaces such as walls, the floor, and

the ceiling in the room. Even with careful loudspeaker

placement and acoustical treatments, there are significant

problems that are caused by room acoustics. These include

reflections from nearby surfaces and standing waves that are

created between large parallel surfaces in the room.

In a home theater the situation is further complicated because

there are several listening locations. The effects of room

acoustics on the sound arriving at each person’s ears are very

different and the result is a listening experience that is

degraded in a different way for every person in the room. It is

not uncommon to have variations in two adjacent seats that

are as large as 10 dB, particularly in the frequency range below

250 Hz.

The solution to this problem is to apply room correction after

precisely measuring how each loudspeaker interacts with the

room. Because the room causes variations in the frequency

response of the loudspeakers that are so large from seat to

seat, it is important to measure each loudspeaker at several

locations in the listening room. This should be done even if

there is only one listener. Measurement at a single location is

not representative of the acoustical problems in the room and

will, in most cases, degrade overall performance.

Audyssey MultEQ XT is the only technology that can achieve

room correction for multiple listeners in a large listening area.

It does so by combining the data collected at several points in

the room from each loudspeaker and then applying correction

that minimizes the acoustical effects of the room and is

matched to the frequency resolution of human perception

(known as psychoacoustics). Furthermore, MultEQ XT

correction is applied both in frequency and time domains and

so there are no artifacts (such as smearing of sound or modal

ringing) that are sometimes associated with traditional

methods of room equalization.

In addition to correcting frequency response problems over a

wide listening area, Audyssey MultEQ XT provides a

completely automated sound system set-up process. It

identifies how many loudspeakers are connected to the

amplifiers and whether they are full-range, satellites, or

subwoofers. If there is a least one subwoofer connected,

Audyssey MultEQ XT determines the optimum crossover

frequency between each satellite and the subwoofer(s). It

automatically checks the polarity of each loudspeaker and

alerts the user if there are any that may be wired out-of-phase

relative to the others. It measures the distance to each

loudspeaker from the main listening position and adjusts the

delays so that sound from each loudspeaker arrives at the

same time. Finally, Audyssey MultEQ XT determines the

playback level of each loudspeaker and adjusts the volume

trims so that all levels are equal.

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