Wilson Audio WATCH Center Channel Series 1 - Manual (Page 25)

25
In general, placement of the speaker in a corner will excite the maximal
number of standing waves in a room and is to be avoided for most direct radiator,
full-range loudspeaker systems. Some benefit is achieved by placing the stereo pair
of loudspeakers very slightly asymmetrically in the listening room so that the
standing waves caused by the distance between one speaker and its adjacent walls
and floors are not the same as the standing wave frequencies excited by the dimen-
sions in the other channel.
C o m b F i l t e r E f f e c t
A special type of standing wave, noticeable primarily in the midrange and
lower high frequencies, is the so-called “comb filter effect.”
Acoustical comb filtering occurs when sound from a single source, such as a
loudspeaker, is directed toward a microphone or listener at a distance. The first
sound to reach the microphone will be the direct sound, followed by delayed
reflected sound. At certain frequencies cancellation occurs because the reflected
sound lags in phase relative to the direct sound. This cancellation is most apparent
where the two are 180 degrees out of phase. There is augmentation at other fre-
quencies where the direct and the reflected sounds arrive in phase. Because it is a
function of wave length, the comb filter effect will notch out portions of the audio
spectrum at regularly spaced intervals.
The subjective effect of comb filter effects, (such as is shown in Figure 4), is
as follows:
S
E C T I O N
2 - I
N
Y
O U R
R
O O M