dbx 166 Quick Start Manual - Page 10
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ABOUT
COMPRESSION
General
The
purpose
of
a compressor
is
to
reduce
the
dynamic
range
of
a
program
and give
you
control
over
its
dynamics. The
i66's
Ratio and Threshold
controls
can produce a wide
variety of
dynamic
-range-reduction
effects,
from
gentie
taming
of overaii
dynamics
to
iimiting of
peaks
to squashing
all
dynamics.
For example,
at
low compression
ratios,
a very low Threshold
setting
can be used
to
reduce
gently the overall
dynamic
range
of a
program. Higher
ratios
with low thresholds
will
provide
leveling for
instruments and
vocals.
High thresholds generally are used
for
limiting
program
levels overall.
Ratios of
6:1
and
higher effectively
prevent outputs
levels
from
much
exceeding
the threshold (assuming the
Output Gain
is
set to
0).
Note
that
compression
of
the entire
program
(produced by low
thresholds) tends to
sound
less
natural at high
ratios.
Ratios
of
perhaps
4:1
and lower
affect
dynamics
to a
lesser
degree,
and
are often used
to tighten
up a
bass
guitar,
snare,
and
vocals.
Moderate
settings typically
are used during
mixdowns
and
for leveling
the
program
in
a broadcast.
The
166's
OverEasy
circuit
prevents compression
at high
ratios
from
sounding too
unnatural. This
is
because
as the
signal
rises
above
threshold, the ratio
changes
graJ^
uaily,
from
1:1
(no
compression)
to that set
by
the front-panel knob.
You
can
put
this
feature
to especially
g<^
use
in
those
situations
when
you need
protection
from
exces-
sive F>eak levels
but desire gentle
compression on most
of the
program.
By
setting
the
threshold at a
moderate
level
and
using a
moderately
high
compression
ratio
(6:1,
10:1,
etc.),
you
will
provide
limiting for signals well
above
threshold
and
gentle
compression
(much
less
than that
set)
for signals at or
below
threshold.
See
the
OverEasy
curve,
p.
2,
to
understand
how
this
works.
It's
always
useful to
watch
the gain-reduction
LEDs
to
see the
amount
of
proc-
essing taking place.
With
practice,
a glance
will
confirm
what
your ears
tell
you
—
that things
are going okay,
or that there's
a
little
too
much
or too
little.
Your
166
can
achieve
desirable effects
with proper
settings derived
from
experience;
whoi
it's
used
too
liberally,
the unusual
results
may
be
suited
to special
effects
only.
Here
are
some
specific situations.
Variations
in
mike
levels
As
the distance
between
vocalist
and microphone changes,
signal levels
change.
Start at
2:1
with a
low
threshold setting to begin
to
smooth
these
out.
With OverEasy,
ratios
up
to
10:1
can be used here
to
good
effect.
Variations
in
instrument
levels
To
achieve
smooth
electric^ass
sound,
start
at
about
4:1.
Strings
and
horns
like-
wise
benefit,
and
strings
will
have
their "sustain" increased.
Note
that large
amounts
of
compression
are
usually
more
audible
in
a
mixed
stereo
program;
if
the separate tracks
were compressed
before mixing to create the
program, compression
is
much
less
notice-
able.
Raising the
signal
out of
a
mix
Since
r^ucing dynamic
range
can
increase the
average
signal level
and
meter
readings,
a
single
track
can be
brought up out
of
a
mix
by
boosting
its
level slightly
and
applying compression.
It's
also possible to
separate certain vocals
and instruments from
an
ciiready
mixed program
by
using
the sldechain; see
p.
10.
-g-