Wilson Audio WATT Series 7 - Manual (Page 41)

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esonAnces
Resonances in listening rooms are generally caused by two sources:
• The structures within the listening room
• The volume of the air itself in the listening room
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TrucTurAl resonAnces
Structural resonances are familiar to most people as buzzes and rattles, but this type
of resonance usually only occurs at extremely high volume levels, and is usually masked
by the music. In many wood frame rooms, the most common type of structural resonance
problem is “booming” of walls and floors. You can test for these very easily by tapping
the wall with the heel of your hand or stomping on the floor. If it is a wooden floor, this is
done to detect the primary spectral center of the resonance. To give you an idea of what the
perfect wall would sound like, imagine rapping your hand against the side of a mountain.
Structural wall resonances generally occur in the low to mid-bass frequencies and add tonal
balance fullness to any system played in that room. They too are more prominent at louder
levels, but their contribution to the sound of the speaker is more progressive. Rattling
windows, picture frames, lamp shades, etc. can generally be silenced with small pieces of
caulk or with blocks of felt. Short of actually adding additional layers of sheet rock or book
shelves, to flimsy walls, however, there is little that can be done to eliminate wall resonanc-
es.
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The volume of air in a room will also resonate at a frequency determined by the size
of the room. Larger rooms will resonate at a lower frequency than will smaller rooms. Air
volume resonances, wall panel resonances, and low frequency standing waves, together,
combine to form a low frequency coloration in the sound. At its worst, it is a grossly exag-
gerated fullness, which tends to obscure detail and distort the natural tonal balance of the
speaker system. Occasionally, however, there is just enough resonance to give a little added
warmth to the sound... an addition some listeners prefer. Tube traps manufactured by the
ASC corporation have been found to be effective in reducing some of these low frequency
room colorations. While custom designed and constructed bass traps, such as perforated
Helmholtz resonators, provide the greatest degree of low frequency control.
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