The Listening Room - Lexicon DC-1 Supplementary Manual

DC-1 Theory
and Design
DC-1 Digital Controller

The Listening Room

If you are using THX speakers, be aware that they have significant design
differences from standard (non-THX) speakers. Extensive information is
available from the manufacturer on their design and on maximizing their
effectiveness in a room. Although not contradictory to those recommenda-
tions, the following guidelines are intended as a generalized reference for
those using standard speakers. Most manufacturers assume that THX sys-
tems will not include separate side and rear speakers. In our experience,
however, adding a pair of widely spread rear speakers to a five channel THX
system makes a very significant improvement to the sound. Such a system
allows the full benefits of Logic 7 and 5.1 Logic 7 to be heard.
The physical characteristics and furnishings in your listening room will
affect the way sound is reflected and dispersed through the room. A great
deal of research has been done in the field of room acoustics and a superb
environment can be constructed with this research in mind. In this discus-
sion, however, we will limit ourselves by assuming that your room is
already built, and that your goal is to get the best sound possible from your
system in that room. Even within this limited scope, there are many factors
which may affect the quality of sound. Fortunately, where there are prob-
lems, there are also some relatively simple solutions.
All rooms have acoustical characteristics determined by their dimensions
and structural materials. The hard surfaces of the room reflect sounds back
and forth in patterns which are likely to interfere with the sounds generated
by your system. The nature of these reflections, and their effects, is dealt
exhaustively in the wealth of material available on Room Acoustics — here
we will simplify by stating that the first general goal is to dampen or diffuse
these echoes — to create an acoustically neutral room which doesn't
interfere with the environment your system creates. The most obvious way
to do this is to add absorbent material to those surfaces from which the most
offensive reflections arise, and to break up undesireable reflective patterns
with uneven surfaces. Fortunately, furnishing the room with carpets,
drapery and furniture goes a long way toward accomplishing this. (Absorb-
ent materials can be commercially-available acoustic panels, fiberglass,
dense foam, drapes, or upholstered furniture. Diffusive materials can be
commercially-available panels, or irregular furniture, such as bookcases.)
Now, what we really want to do is "tune" the room to maximize the clarity
of dialog within a localized front soundstage, and to create a diffuse, non-
localized soundfield for effects. This can often be done by adjusting speaker
placement, by altering room furnishings or by some combination of both,
but to do this effectively, we must look briefly at the kinds of interference
you may encounter. Following are some basic problems and suggested
solutions.
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