Reverberation And Reality; Using The Reverb Programs - Lexicon 960L Owner's Manual

960L

USING THE REVERB PROGRAMS

Music recorded in a typical studio sounds dull. In a per-
formance space the music is enhanced by reverberation,
but even in an ideal space capturing that reverberation
can be chancy. Lexicon reverberators solve this problem
by enabling you to generate exactly the reverberance
that your recordings call for, even with multitrack originals
made in imperfect spaces. You can make your listeners
feel they are sitting in a real concert hall, even though
they are in a small room with hard, flat walls. The object of
the 960L is to create, in the studio, the acoustics of any real
or conceivable space, and to reproduce these acoustics
using the full directional capabilities of a modern surround
system.

REVERBERATION AND REALITY

The acoustics of a given space are defined by its reflect-
ed energy – that is, the way sound is reflected and re-
reflected from each surface.
dimensions of the space, the complexity or flatness of the
surfaces, the frequency characteristics of each surface's
energy absorption, and the distance and direction of
each surface to the listener. In addition, in large spaces
there is a high-frequency rolloff caused by the sound's
passage through air.
It is in principle possible to model the reflected energy pat-
tern in a specific space, either real or imagined, and to
reproduce this pattern as closely as possible through a
five-loudspeaker array. Alternately, one could measure
the reflection pattern from a specific source point in a real
space to a specific receiver position, and reproduce this
pattern through five loudspeakers. One might expect this
technique would yield the most accurate sonic represen-
tations of halls and rooms.
Alas, the illusion of reality is not so easily achieved. First,
real spaces are themselves a compromise. Small rooms
(and stage houses) tend to provide a sense of blend and
distance to music, but provide little warmth and envelop-
ment, and often can make the sound colored or muddy.
Large rooms can provide envelopment, but often the
sound can be too clear and present, with the instruments
seemingly stuck in loudspeakers.
To make matters worse, in a real space every musician will
have a completely different reflection pattern from every
other musician, and every listener will have a different pat-
tern from every other listener. In addition, reproduction of
a given sound field through a loudspeaker array is only
possible if the listener occupies a single, known position. If
our goal is to create a believable room impression over a
wide listening area – and this should be our goal – then we
better do something else.
This is affected by the
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Using the Reverb Programs
Our solution has been to study the physics and the neurol-
ogy of human hearing, to discover the mechanisms by
which reflected energy patterns create the useful per-
ceptions of distance and envelopment, and to discover
how to recreate these perceptions without compromising
clarity. Using a knowledge of these mechanisms we can
create reverberation devices that can give the desired
acoustic impressions – rooms that sound plausibly real, but
that give the recording engineer complete control over
the sense of distance and the sense of envelopment.
These rooms seem real, but they are not.
designed and adjusted by the engineer to the specific
needs of the recording, and they create their magic uni-
formly over a wide listening area.
To see how this works, consider a concert space – a large
hall. In this space we hear a sonic event as a whole pack-
age of sounds, consisting of direct sound, various early
reflections, and finally the reverberant tail. The sound that
reaches us directly from the performer tells us the horizon-
tal (and possibly the vertical) direction of the sound
source; the reflections that follow give us cues for deter-
mining the distance to the source, and give us some infor-
mation about the space.
Yet describing acoustics through the concepts of direct
sound, early reflections, and reverberation is misleading
from the point of view of human perception. Direct sound,
early reflections and reverberation are only meaningful
when the sound source is a very short impulse, like a pistol
shot. Real sound sources produce sound events of finite
duration (notes). The duration of a note is typically longer
than the time between the direct sound and the early
reflections. The length of time a note is held dramatically
changes the acoustics we perceive, as short notes excite
primarily early reflections, and long notes excite the later
reverberation.
For example, in real rooms the direct sound is primarily per-
ceived at the onsets of sound events (notes). When a
sound starts abruptly there is a brief instant where we can
hear the direct sound all alone, before it is corrupted by or
overwhelmed by reflected energy. In this brief interval we
can detect the direction, and sometimes the elevation of
the source. The so-called "early reflections" are only audi-
ble after a note starts. They are sometimes audible as a
change in localization or timbre while a note is held, but in
general they affect perception most strongly only after a
note ends. These reflections are heard in the space
between notes – and then often only as a tendency to
make the notes sound longer than they actually are.
Reverberation also is nearly always heard after the ends of
notes, either in the space between notes, or at the end of
whole phrases. Reflections alter our senses of direction,
distance, and hall shape in ways that depend on the
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