10
iEQ
iEQ User Manual
AFS™
First introduced in the DriveRack PA and 260 processors, the iEQ-15 and iEQ-31 both utilize dbx’s
proprietary AFS™ (Advanced Feedback Suppression) algorithm, providing effortless feedback
elimination� AFS uses Precision Frequency Detection and state-of-the-art processing to pinpoint, with
more accuracy, the exact frequency where feedback occurs� In the past, graphic equalizers were used
to eliminate feedback from a system� This was an acceptable method for eliminating feedback, but
when this method was precision tested, the result clearly showed that a single 1/3 octave EQ slider
was removing approximately half of the signal power� With AFS, the algorithm removes the feedback
automatically and the proprietary, precision AFS filters use narrower notch filters for removing the
feedback, thereby retaining the sonic integrity of the source material� This is what sets AFS apart from
using traditional EQ or other feedback elimination processors for feedback removal� The following
graph shows a comparison between AFS filters, the filters available in other feedback eliminators, and
conventional graphic EQ filters:
Competitor’s
Feedback
Elimination
1/3 Octave EQ
dbx AFS™
AFS utilizes two types of filters, they are:
• Fixed Filters - Fixed filters are used for ringing out a sound system before the system is
to be used, thereby notching out the most offending feedback frequencies within the venue�
Fixed filters are automatically stored in the iEQ processor, even after a power cycle, until
cleared by the user� These filters are typically best suited for fixed installation� To use the Fixed
filters, you must configure the iEQ for 6-Fixed/6-Live mode as described in the “Power-Up
Modes” section of this manual�
• Live Filters - Live filters work in the background and search for feedback during the
performance� Once all Live filters have been set, the filters will begin to round-robin (if new
feedback occurs, the first Live filter set will be lifted and placed in the new frequency location
to eliminate the new feedback)� Live filters are cleared when the iEQ is power cycled or when
cleared by the user�
NOTE: AFS works best when the gain structure of the sound system has been optimized� During use,
the iEQ’s 0 dBu LED in the OUTPUT LEVEL meter should light with the +10 dBu LED lighting
occasionally�
Clearing Filters
To clear the AFS filters, press and hold the channel’s AFS button until the adjacent LED meters begin to
flash, then release� This clears all filters which have been set in the channel�
IMPORTANT! It is advised to turn down the system’s gain before clearing the AFS filters� If AFS filters
are set and feedback suppression is occuring, clearing the filters without turning down the system’s gain
could cause the system to go into immediate feedback�
For more detailed information regarding the AFS algorithm, please see the AFS white paper located at
www�dbxpro�com�
Operation
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