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Surround sound - explanatory notes
General information:
The following section is not concerned directly with the
operation of your
DD 1535 R
decoder, but is rather
intended to explain some of the terms which arise in
connection with surround systems. It is intended to help
you understand and exploit the facilities and capabilities
of your
DD 1535 R
to the full.
As we all know, a normal stereo recording has two
channels - left and right. When stereo material is
reproduced in your listening room, the entire sound event
takes place on an imaginary stage which covers the
space between the two loudspeakers.
The listener is able to locate specific sound events over
the width of the stage; with good recordings there is also
a slight impression of depth, i. e. behind the speakers.
Nevertheless, normal stereophonic reproduction always
leaves the listener isolated from the event.
As a result it is impossible to recreate the excitement of a
live atmosphere, as in a real concert hall, since the
acoustics of the concert hall are crucially influenced by
sound reflections from the side and back walls, the floor,
the ceiling, and from objects inside the hall.
The reflected sound comes from any number of
directions - not just from the front. If a sound event is to
be reproduced with real fidelity, it therefore follows that a
proportion of the sound must emanate from all directions
in the room, that the “reflections” must be timed
accurately, and that they must be generated at a realistic
level.
Reproducing television sound via a conventional stereo
system is problematic, because it is often impossible to
locate dialogue on the screen itself.
A further point is that exotic sound effects have been in
use in the cinema since the 1950’s, using proper multi-
channel sound systems. These effects are often crucial
to the overall impact of a film, but they cannot be
reproduced at home with a conventional stereo sound
system.
Over the last few years surround technologies have been
developed which make it possible to experience all these
effects within the listener’s own four walls, with the result
that a far greater simulation of reality is possible than
with conventional stereo.
For an effective surround system we always recommend
the installation of a centre loudspeaker, which is installed
below or directly above the TV set. This loudspeaker
helps greatly in locating particular sound events
(especially dialogue) on the TV screen itself.
Types of reproduction
The
DD 1535 R
makes available a range of different
types of reproduction:
multi-channel mode,
mono/stereo mode
and
sound fields.
The surround receiver ‘remembers’ the setting for each
input, and reverts to the mode of operation which was
last used for that input when you switch to it from another
input.
Multi-channel mode (surround):
Mode of operation for the reproduction of multi-channel
programmes (e. g. DOLBY Pro Logic II, DOLBY
DIGITAL, dts, etc.)
Digital
multi-channel signals are detected by the
encoding methods employed, and the surround receiver
automatically sets the correct loudspeaker assignment.
The current reproduction mode is displayed on the front
panel screen.
For
analogue
input signals the correct mode of
operation cannot be detected automatically by the
decoder. In this case the surround receiver always
reverts to Dolby Pro Logic II decoding. If the signal is
actually in a different form (stereo, mono - see below),
then the mode must be set manually instead of surround
mode.