Standing waves – Wilson Audio WATCH Center Series 3 User Manual

Page 15

It adds harshness to the upper midrange and treble by storing time-domain

smearing energy.

It destroys the delicate phase relationships, which help to establish an accu-

rate soundstage.

Slap echo (see Figure 1) is a common acoustical problem in the typical domestic lis-

tening room because most of these rooms have walls with a hard, reflective nature, only

occasionally interrupted by curtains, wall art, or drapes. The best (but least practical)

solution to eliminate slap echo is nonparallel walls. This is because, rather than support

slap-echo, nonparallel walls allow the sound to diffuse. This approach can be accounted

for during the construction process. For existing rooms, slap echo can also be controlled

entirely by the application of absorptive materials to the hard surfaces. These are absorp-

tive materials that can be used to ameliorate slap echo:

Illbruck Sonex®

Air duct board

Large ceiling to floor drapes

Carpeting to wall surfaces

In many domestic listening environments, heavy stuffed furnishings reduce slap echo

somewhat. Unfortunately, their effectiveness is not predictable. Diffusers are sometimes

also used to very good subjective effect, particularly in quite large rooms. Sound absor-

bent materials such as described above will alter the tonal characteristic of the room by

making it sound “deader,” less “bright and alive,” and “quieter.” These changes usually

make the room more pleasant for conversation, but sometimes render it too dull in the high

frequencies to be musically involving. Soundtrack effects will be more localized. However,

over-damping the room skews the tonal balance unnaturally toward the bass, and also com-

presses dynamics, robing the system of musical life excitement.

Diffusers, on the other hand, do not affect the tonal balance characteristic of the

room as much. Placed properly, diffusers create a smoother and more open sound. Some

diffusers, due to their construction, create narrow midrange peaks and suck out the warmth

region. Do not use diffusers on the wall behind the speakers or on the sidewalls directly

beside the speakers. It is our experience that all of these room treatment devices should

be used judiciously.

Standing Waves

Another type of reflection phenomenon is “standing waves.” Standing waves cause

the unnatural boosting or accentuation of certain frequencies, typically in the bass, to be

IGURE

6 – C

OMMON

OOM

EFLECTION

ROBLEMS

E C T I O N

3 . 2 — R

O O M

C O U S T I C S

W A T C H C

E N T E R

H A N N E L

E R I E S

3 O

W N E R

’

A N U A L

W i l s o n A u d i o S p e c i a l t i e s