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dbx 166xs
Section 4
Operating Notes
In circumstances where the 166xs is expected to cause no change in gain unless an
emergency arises (wildly excessive levels), some operators set Hard Knee mode On, the RATIO
to ∞:1, and the THRESHOLD to the highest permissible level. As with preventing digital
overload, the 166xs PeakStop limiter can be used instead of or in combination with the
166xs compression.
As a general rule, compressors should be as close to the amplifiers as possible in the signal
chain. If the 166xs is placed before the EQ (equalizer), for example, a potentially damaging
boost in the EQ won't be seen by the 166xs and the speakers may be damaged. (see Multi-way
speaker systems, page 19). 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, one 166xs can be used for each stereo band (low,
low-mid, mid, etc.).
Raising Average Level in PA Systems
Limiting (i.e., compression at high ratios like ∞:1) also benefits intelligibility by allowing
low-level input signals to be reproduced through the system at higher volume. In a musical
performance, this provides additional intimacy so that a vocalist's whispers are heard
more clearly. The OverEasy curve available with the 166xs permits a very high amount of
compression (RATIO of 10:1 or greater) to be used in many situations. This allows dynamic
speakers, vocalists and other musicians to concentrate on their presentation or performance
without worrying about the ill effects of volume changes.
Using Your EQ to Reduce Feedback in Live Settings (Indoor and Outdoor Concerts,
Churches)
You can use your 166xs and EQ (equalizer) to reduce feedback in clubs, churches, outdoor
concerts and other live settings. Patch or insert the 166xs into the main output of a mixer,
set the 166xs to Hard Knee mode and slowly increase OUTPUT GAIN until the first feedback
"ring" occurs, then set up the 166xs with its RATIO at ∞:1 and THRESHOLD low. The 166xs
will catch the first feedback ring and hold it as a constant tone so you can adjust your EQ
to minimize it. Continue to increase your console gain and set your EQ until the next 3 or 4
"ring" frequencies have been compensated for.
The 166xs as a Line Amplifier
To use the 166xs as a line amplifier, adjust the RATIO control fully counterclockwise (1:1
position), THRESHOLD fully clockwise (+20), PeakStop to +20 and OUTPUT GAIN to whatever
setting is required for the application. Remember, excessive gain may lead to output clipping
of high level signals. To add compression, adjust the RATIO and the THRESHOLD controls to
the desired settings.
Frequency-Weighted Compression (Sidechain Application)
It is possible to separate certain vocals and instruments from a mix by frequency-weighted
compression. With an equalizer (such as a dbx 2 Series, 12 Series or 20 Series EQ) inline
ahead of the SIDECHAIN INSERT (but not in the audio path), the equalization settings do not
shift the timbre or frequency response of the audio signal. They merely alter the threshold
response of the compressor on a "frequency-weighted" basis.
With this arrangement, raising certain frequencies on the equalizer causes them to be
suppressed in the audio signal. A relatively high THRESHOLD setting can allow normal
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