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Specific Applications
Smoothing
out
variations
in microphone levels
When
the
distance between a vocalist and a mi-
crophone changes, variations in signal level occur.
To smooth out
these
variations, start
with
the
160XT
adjusted
for
a
low
COMPRESSION RATIO
(e.g.,
4:1) and adjust the THRESHOLD control for
optimum results,
then increase
COMPRESSION
RATIO if necessary.
Due to the
gentle
Over
Easy
characteristic of your
160XT
you will find
that
even
fairly high ratios
are
handled transparently
.
Smoothing out
variations in musical instrument
levels
To achieve a smoother electric
bass
sound, com-
press the instrument's output with
a
ratio
of about
4:1 (the COMPRESSION
RATIO
control set at ap-
proximately
12:00).
Compression lessens
the loud
-
ness variations among the strings and
increase
s
the
sustain.
Other
instruments, such
as
horn
s,
vary
in
loudness
depending on the
not
e
being played, and
benefit simi
larly.
NOTE: When
compressing
a
stereo
program
with
a pair of 160XTs, the factors affecting a com-
pression curve and the actual compression ratio
and threshold settings, are like those previously
covered
with reference
to
single channels
of pro-
gram
material. However, it will generally be found
that
large
amounts of
compress
ion
are more audi-
ble in a
mixed
stereo
program than they might be
Specific Applications
Preventing tape saturation
With programs of widely varying
levels,
com-
pression can prevent recording
levels
from saturat-
ing
tape tracks
(see
Frequency-weighted
compression,
page
20).
Speaker
protection
Compressors are
frequently used
to prevent ex-
cessive
program
levels from
damaging
drivers in a
sound-reinforcement
syste
m.
Limiting also benefits
intelligibility by
allowing low -level
input signals to
be
reproduced through the
system at
higher
vol-
ume.
In a musical performance, this provides addi-
tional
intimacy
as
the
vocalist's whispers are
heard
clearly at every seat in
the house. The Over
Easy
curve
available with
the 160XT permits
a very high
amount of COMPRESSION (10:1 or greater)
to
be
used
in many
situations. Vocalists and musicians
don't get
the
sense of being held
back, but high av
-
erage
levels can be
maintained
without speaker
damage due
to
excessive
heat
buildup.
In circumstances where the 160XT
is
expected to
cause no change in gain unless an
eme
rgency
arises (wildly excessive levels) some operators
se
t
the COMPRESSION RATIO to
00
:l,
the
THRESH-
OLD to
the highest
permissible level, and operate
the
unit in hard-knee
mode. As a general rule, the
compressors should be
as
close
to the amplifiers as
possible
in
the
signal chain. If
the 160XT
is placed
before the EQ, for example, a potentially damaging
on
the
separate
tracks that
were
mixed to
create
the
program.
Raising
a
signal out of a mix
Since reducing
dynamic range increases the
aver
-
age
signal level
by
a
small amount, a single track
can be raised out of a mix
by boosting its level
slightly and applying compression.
It is also
possi-
ble
to
separate certain vocals or instruments from a
mono program already
mixed by frequency-
weighted compression (see page 20).
Using your
EQ
to reduce feedback in live settings.
You can
use
your
160XT and
EQ
to reduce feed
-
back
in
clubs or
halls by placing the
160XT at
oo:l,
Hard Knee, and a
low
threshold. Increase control
gain until
the first
feedback "ring" occurs.
The
160XT will catch
it, and hold it
as a constant
tone
so you
can
adjust your EQ
to minimze
it. Continue
to
increase your
conso
le
gain and set your EQ
until
the
3 or
4 "ring" frequencies have been compen-
sated
for.
dbx 160XT
boost
in
EQ won't be seen
by
the
160XT
and
the
speakers
may be damaged. (see
Multi-way
speaker
systems, page 12).
For maximum
sound
pressure
levels, large
sound reinforcement systems
fre-
quently use
a separate compressor on
each output
of
the
electronic
crossover(s).
For a stereo sound-re-
inforcement system, stereo strapping cables should
be
run
between
the 160XTs in
each
band
(low-low,
mid-mid, etc.).
The 160XT as
a
line amplifier
To use
the 160XT
as a line amplifier, adjust
the
COMPRESSION ratio control
to fully
counterclock-
wise
(1:1 position),
THRESHOLD
to full
clockwise
position(+
10)
and OUTPUT GAIN
to
whatever set-
ting is required
for the application.
Remember
that,
as with any amplifier, excessive gain may
lead
to
output clipping of high
level signals.
To add com-
pression,
adjust the COMPRESSION ratio and the
THRESHOLD controls
to the
desired settings.
79
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