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world’s finest distributors and dealers, if
you have any problems they should be
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The subject of room
acoustics
Acoustics is a complex subject and this
text should be treated for what it is, a
simple but for some, informative guide.
For a more in-depth understanding you
would need to refer to a whole range of
texts on the subject. The most important
outcome of this should be the greater
appreciation of the role, played by the
room on the overall sound of the audio
system.
The air contained within the room is the
link between the output of the
loudspeaker and your ear. How air
behaves is dependent upon the attributes
or character of the room. It follows that a
better understanding of basic acoustics
and what facets cause the most influence
in the room will assist in making decisions
about the way in which the room and
subsequently the system can be improved.
Room types fall between two extremes. A
room can be
“dead”
on the one hand
(full of highly energy absorbent materials
and complex diffusing structures) or very
“lively”
on the other (few reflective
surfaces and a high proportion of very
reflective, hard, non absorbent surfaces).
As so often is the case, a balance of
materials is commonly preferable to one
extreme or the other. The correct balance
is the goal for the end user.
Room attributes which can be
easily changed
The contents of the room impact greatly
upon its overall acoustic character. As you
would expect, hard surfaces like glass and
concrete tend to reflect a broad band of
acoustic energy. Complimentary materials
that are soft and thick in section such as
heavy natural fibre curtains will tend to
absorb a broad band of frequencies.
What are Standing waves?
Sound waves reflecting between two
parallel walls set up resonance modes
when
one half, or a whole multiple of
one-half, the wavelength of the sound
wave is equal to the distance between
the walls.
These resonance modes are referred to as
“standing waves”.
In loudspeakers with
parallel walls these waves will cause
distortions. The standing waves in your
room will distort the frequency response
of your system sympathetically boosting
certain frequencies.
If a certain standing wave frequency is
acoustically isolated from its modal
neighbours, its effect is more likely to be
audible and problematic. This can
compromise
the
accuracy
of
any
loudspeaker.
Middle and High Frequency
Room Characteristics
The middle and high frequencies are
affected more by room contents rather
than room shape. The surfaces and how
they reflect, absorb or diffuse the acoustic
energy will tend to describe the “sound”
of a room. Like all energy, acoustic energy
cannot be destroyed; it can only be
converted into something else or
reflected. The shape of the surface will
determine how it is reflected and the
material will determine whether it is
absorbed. All rooms have a particular
sound, and to appreciate what influences
are present in your room you should be
aware of how the objects in your room
will respond to sound.
Sound waves behave in the same way as
light waves or "rays" and so imagine the
driver to be a floodlight.
