Lexicon 960L - Manual (Page 52)

960L Owner’s Maunal Using The Reverb Program
Music recorded in a typical studio sounds dull. In a
performance 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
reflected energy – that is, the way sound is reflected
and re-reflected from each surface. This is affected by
the 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
pattern 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 representations 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 envelopment, 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 pattern 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.
Our solution has been to study the physics and the
neurology of human hearing, to discover the
mechanisms by which reflected energy patterns create
the useful perceptions 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. They are designed and adjusted
by the engineer to the specific needs of the recording,
and they create their magic uniformly 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 package 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 horizontal (and possibly the vertical)
direction of the sound source; the reflections that follow
give us cues for determining the distance to the source,
and give us some information 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
perceived 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 audible 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
Using the Reverb Programs
5-1