The Afs Filters; Fixed Filters; Live Filters; Filter Widths - dbx AFS2 Owner's Manual

The AFS Filters

AFS offers two types of filters: Fixed and Live. Fixed filters are set during the initial AFS ring-out procedure. Live filters are
then enabled for protection against new occurrences of feedback during system use. The Live filters in the enhanced AFS
algorithm in the AFS2 can better distinguish between program material and feedback, dramatically lowering the probability of
false Live filters being set on feedback-like music material, such as flute. When you run the AFS Wizard, AFS will automatically
switch between Fixed and Live Mode operation.

Fixed Filters

Fixed filters are active when the FILTER MODE parameter in the AFS OPTIONS menu is set to FIXED. Fixed filters cannot
differentiate between what is music and what is feedback, so these filters are used to initially ring out the sound system before
use and notch out frequencies which are most prone to feedback in the system/venue. This allows the system gain to be
raised without introducing feedback.
NOTE:
When in Fixed Mode, the Fixed filters will be allowed to move around and/or widen in order to center themselves
better on offending feedback regions. Upon switching to Live Mode, all Fixed filters will become truly 'fixed' .
Fixed filters are just that, 'fixed' . They will remain set – even after power cycling the AFS2 – until they are cleared by the user
or a different preset is loaded, in which case all set Fixed filters in the loaded preset will be set.

Live Filters

Live filters are active when the FILTER MODE parameter in the AFS OPTIONS menu is set to LIVE. Live filters are smarter
than Fixed filters. They have the ability to detect feedback within complex program material. This makes them ideal for
protecting the system from feedback as conditions change during the performance. Live filters also have the ability to detect
when they are no longer needed and can intelligently remove themselves from the chain, effectively restoring sonic fidelity and
freeing up Live filters for use. The parameters that control this behavior are the LIVE LIFT and LIFT AFTER parameters. See
'The Menus & Parameters' on page 24 for additional information on these parameters.
If a condition is met where all Live filters have been set, they will begin to round robin – meaning that if all Live filters have
been set and new feedback occurs, the first Live filter set will be released then re-set at the new feedback frequency location.
AFS will continue to round robin through the Live filters as long as all Live filters are set and new feedback is detected.

Filter Widths

The AFS2 offers three filter width options, they are: SPEECH, SPEECH/MUSIC, and MUSIC. The selected option controls the
width of the notch filter used to remove the feedback. These options can be found under the CONTENT MODE parameter in
the AFS OPTIONS menu. See 'AFS Options Menu' on page 24 for further information on the CONTENT MODE options.
NOTE:
All AFS filters are allowed to widen if necessary in order to tackle wider feedback regions.
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