T+A Elektroakustik K 6 - Manual (Page 9)

9 Operation
Surround sound - explanatory notes
General information
The following section is not concerned directly with the
operation of your K6, but is rather intended to explain
some of the terms which arise in connection with sur-
round systems. It is intended to help you understand and
exploit the facilities and capabilities of your K6 to the full.
As we all know, a normal stereo recording has two chan-
nels - 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 direc-
tions - 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 accu-
rately, 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 repro-
duced 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 center loudspeaker, which is installed
below or directly above the TV set. This loudspeaker
helps greatly in locating particular sound events (espe-
cially dialogue) on the TV screen itself.
Types of reproduction
The K6 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 when you switch from one input to another.
Multi-channel mode (surround)
Mode of operation for the reproduction of multi-channel
programmes (e.g. DOLBY Pro Logic, DOLBY DIGITAL,
dts, etc.).
A digital multi-channel signal is detected by its encoding
method, and the K6 automatically sets the correct loud-
speaker assignment. The current reproduction mode is
displayed on the front panel screen.
For analogue input signals the correct mode of opera-
tion cannot be detected automatically by the decoder.
In this case the decoder always reverts to Dolby Pro
Logic 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.
Dolby Pro Logic II Surround
In this process several independent signal channels are
recorded using two channels and a special encoding
process. Since this process only requires two recording
channels, it is compatible with many picture / sound
systems which are already widely in use (CD, video
recorder, TV etc.).
The information is decoded at playback time and repro-
duced in the listening room via four (left, right, 2 x sur-
round) loudspeakers, although five speakers (with an
additional front center speaker) are preferable. Dolby
Surround encoded material is currently available mainly
in the film and video arena, recorded on video cassettes
and DVDs, but many television programmes are now
being produced and transmitted using Dolby Surround.
Dolby Digital
Dolby Digital is a digital
multi-channel
surround
system which was
developed specifically for
spatial sound reproduction
in connection with cinema
films. The process utilises
five
separate sound
channels: three front
channels (left, center,
right) and two surround
channels.
A sixth
independent bass effect
channel is also present,
catering for low frequency effects (LFE). That is why
such systems are said to offer 5.1 channels.
In comparison with Dolby Pro Logic, Dolby Digital pro-
vides two independent surround channels which provide
genuine spatial stereo sound, offering the same realistic
stereo reproduction as provided by the front channels.
The integral Dolby Digital decoder provides the means of
obtaining a genuine digital Dolby stereo cinema presen-
tation in your own living room. The discrete digital re-
cording process and the five playback channels guaran-
tee a very wide dynamic range and accurate spatial
orientation.
The dynamic range is the difference in volume between
the quietest and loudest passages of a recording. The
original soundtrack of a film generally features an ex-
tremely wide dynamic range which the K6 can reproduce
in full.