ART Pro Audio XL231 - Dual 31-Band, 1/3 Octave, Graphic EQ - Manual (Page 9)

ART XL 231 Dual 31 Band, 1/3 Octave Extended, Long Throw, Professional Equalizer
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curves, and, have less selectivity so the Trim controls don’t have a “sound” as a typical
tone control will.
The Trim controls are typically used after the overall equalization has been set, yet the
balance between highs, mids, and lows needs to be adjusted. For example, when
providing sound at a venue, the equalizer may be set during a sound check. When the
audience later fills the room, the sound may get duller due to the added high frequency
absorption. The HI trim may be increased to eliminate the dullness without the need to
re-equalize the entire system. Note also that in either indoor or outdoor events, changes
in temperature or humidity can affect high frequency absorption and the Trim controls
are useful to help compensate for these changes.
LEVEL CONTROL
This controls the output signal level from the equalizer. Unity gain can be set by
adjusting this knob so that as you toggle the Bypass switch the overall level sounds the
same.
Signal levels should be kept normalized through the equalizer. That is, the signal level,
when bypassed, should be the same (or a little lower) than when active. One reason for
this is if the equalizer loses power (which causes the unit to go into bypass), the signal
will be equal or lower than the active equalizer gain. This will ensure that a signal with
undesirably higher levels will not be passed inadvertently.