dbx 160X - Page 13

OPERATING NOTES
dbx Professional Products
Speaker protection
Compressors are frequently used to prevent excessive program levels
from damaging drivers in a sound-reinforcement system. Limiting also
benefits intelligibility by allowing low-level input signals to be reproduced
through the system at higher volume. In a musical performance, this pro¬
vides additional intimacy as the vocalist’s whispers are heard clearly at
every seat in the house. The OverEasy 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 average 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 emergency arises (wildly excessive levels) some operators
set the COMPRESSION RATIO to °°:1, the THRESHOLD 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 po¬
tentially damaging boost in EQ won’t be seen by the 160XT and the
speakers may be damaged, (see Multi-way speaker systems, page 14).
r For maximum sound pressure levels, large sound reinforcement systems
frequently use a separate compressor on each output of the electronic
crossover(s). For a stereo sound-reinforcement 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 counterclockwise (1:1 position), THRESHOLD to full clock¬
wise position (+10) and OUTPUT GAIN to whatever setting is required for
the application. Remember that, as with any amplifier, excessive gain
may lead to output clipping of high level signals. To add compression, ad¬
just the COMPRESSION ratio and the THRESHOLD controls to the de¬
sired settings.
Side-chain applications
Frequency-weighted compression
It is possible to separate certain vocals and instruments from a mix by fre¬
quency-weighted compression. With an equalizer inserted ahead of the
detector input (but not in the audio path), the equalization settings do not
shift the timbre or frequency response of the audio signal. They merely al¬
ter the threshold response of the compressor on a “frequency-weighted”
basis (see Figure 6).
12