Denon AVR-3805 - Manual (Page 90)

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Surround back speakers
A 6.1-channel system is a conventional 5.1-channel system to which the “surround back” (SB) channel has been added. 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 FL C SW FR
SR ch SL ch
SL ch SR ch
SB ch
Change of positioning and acoustic image
with 5.1-channel systems
With this set, speaker(s) for 1 or 2 channels are required to achieve a 6.1-channel system (DTS-ES, etc.). Adding these speakers, however,
increases the surround effect not only with sources recorded in 6.1 channels 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 (see page 62) are compatible with 7.1-channel playback, so you can enjoy 7.1-channel sound with any signal source.
Movement of acoustic image from SR to SL
Change of positioning and acoustic image
with 6.1-channel systems
Movement of acoustic image from SR to SB to SL
2 Number of surround back speakers
Though the surround back channel only consists of 1 channel of playback signals for 6.1-channel sources (DTS-ES, etc.), we recommend using
two speakers. When using speakers with dipolar characteristics in particular, it is essential to use two speakers.
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.
2 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
6.1 surround or DTS-ES Matrix 6.1 mode. Check the surround effects of the various modes before selecting the surround mode.