A-16
Appendix Mark Levinson
How Room
Modes Affect
the Listener
Room modes affect the frequency response you hear in several ways. The
most pronounced effect of room modes is to make certain frequencies too
loud. But the most difficult to solve is the tendency of some resonances to
linger in the room after the speaker has stopped vibrating. A very strong
resonance can linger as long as half a second and in the worst cases, the
sound will also have a distinct pitch.
These lingering resonances are not always noticed by listeners because the
frequencies are usually too low to be discernible as a detail unless the
listener specifically listens for them. But they do present a serious problem
because the lingering sound often obscures the following details of the
music or soundtrack. For example, the lingering sound from a kick drum
could mask the details of the following vocal passage. Subjectively, you
might feel as if you were listening to the music through a layer of gauze.
You might try to fix things by adjusting the overall volume or by tweaking
your audio controls. However, none of these fixes can provide satisfactory
results as each can cause detail loss in other areas.
For example, turning down the bass sufficiently to solve the problem with
the kick drum requires all of the bass frequencies to be turned down,
which could leave the rest of the score with too little bass.
Correcting
Room Modes
The too-slow decay of a resonance mode can be corrected only by
applying the proper filter. The severity of a resonance mode is defined by
its “Q” value, or Quality Factor. The higher the Q of a resonance, the
bigger its amplitude and the slower its decay. Proper treatment of a
resonance requires a filter with not only the correct frequency and depth,
but also the correct Q.
The Room EQ calibration of the Nº502 identifies room resonances and
measures both their Q and frequncy in a highly precise manner. Using
this information, the calibration then applies the proper parametric filters
to neutralize these resonances.
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