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Additional Information

Surround back speakers

The THX Surround EX format adds new “Surround Back” (SB)
channels to the conventional 5.1-channel system. This makes
it easy to achieve sound positioned directly behind the
listener, something that was previously difficult with sources
designed for conventional multi surround speakers. In
addition, the acoustic image extending between the sides and
the rear is narrowed, thus greatly improving the expression of
the surround signals for sounds moving from the sides to the
back and from the front to the point directly behind the
listening position.
FL C
SW
FR
SR chSL ch
Change of positioning and acoustic image
with 5.1-channel systems
Movement of acoustic image from SR to SL
FL C
SW
FR
SL ch SR ch
SB ch
Change of positioning and acoustic image
with THX Surround EX system
Movement of acoustic image from SR to SB to SL
Speaker(s) for one or two channels are required in order to
achieve a THX Surround EX system with the AVR-4806CI.
Adding these, however, allows you to achieve stronger
surround effects not only with sources recorded in THX
Surround EX, but also with conventional 2- to 5.1-channel
sources. The WIDE SCREEN mode is a mode for achieving
surround sound with up to 7.1 channels using surround back
speakers, for sources recorded in conventional Dolby
Surround as well as Dolby Digital 5.1-channel and DTS
Surround 5.1-channel sources. Furthermore, all the Denon
original surround modes ( page 61 ~ 63) are compatible
with 7.1-channel playback, so you can enjoy 7.1-channel
sound with any signal source.

¢Numbers and types of surround back speakers

With THX Surround EX, the surround back channel
consists of one channel of playback signals, but we
recommend using two speakers. The modes that use the
new ASA technology from THX ( page 152) are most
effective when using two monopole type surround back
speakers placed close together.
Using two speakers results in a smoother blend with the
sound of the surround channels and better sound
positioning of the surround back channel when listening
from a position other than the center.

¢Placement of the surround left and right channels

when using surround back speakers

Using surround back speakers greatly improves the
positioning of the sound at the rear. Because of this, the
surround left and right channels play an important role in
achieving a smooth transition of the acoustic image from
the front to the back. As shown on the diagram above, in
a movie theater the surround signals are also produced
from diagonally in front of the listeners, creating an
acoustic image as if the sound were floating in space.
To achieve these effects, we recommend placing the
speakers for the surround left and right channels slightly
more towards the front than with conventional surround
systems. Doing so sometimes increases the surround
effect when playing conventional 5.1-channel sources in
the THX Surround EX mode. Check the surround effects of
the various modes before selecting the surround mode.