JBL PRX ONE, User Manual

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4. dbx DriveRack Output is a line of hardware products produced by Harman’s dbx brand. These rack mount signal
processors provide detailed control for final processing and crossovers before feeding the mix to one or more
speakers. This DriveRack functionality embedded into PRX ONE is designed to optimize the combination of
speaker and Pass Thru outputs built into this JBL speaker.
a. AFS, or Automatic Feedback Suppression, is a combination of processing that can enable the user to add
up to 3 dB more total gain to their output before getting audio feedback back in through the mix inputs. dbx
AFS does this using a combination of auto-sensing and very tight width parametric EQs before the output
master EQ. Locked filters can be setup before an event as “fixed” filters. Plus live AFS filters can be turned
on to continue chasing the latest feedback frequency risks during an event, such as changes caused by
handheld microphones moving positions and directions while on stage.
i. Stage setup best practices are always recommended for best results to avoid feedback,
in combination with the AFS processing system. Microphones have less chance of
contributing feedback if they follow the following position standards on stage:
. Microphones should be behind the front plane of the speakers.
. Microphones should be least two meters to the left or right of the speakers.
b. “AFS by dbx” On/Off selection toggles the AFS processor on or off.
c. “Live AFS” On/Off selection toggles the live AFS filters on or off. Live filters are best for catching feedback
on stage from microphones that are moving around the stage. Turning on “Live AFS” is the fastest, easiest
way to start using AFS processing.
d. “Reset Live Filters” will reset all live filters, prompting the filters to reset and start over in their discovery of
potential feedback frequency risks.
e. “Learn Fixed” starts the automatic discovery and setup of the Fixed AFS filters. While the microphones are
plugged in before the show and speakers are turned on, enable the “Learn Fixed” function. Then walk over
to the nearest mics and speak loudly into them to try to induce feedback. If no feedback is found, turn up
the main volume slowly until feedback rings and is suppressed by a fixed AFS filter. Each time the speaker’s