Using The Adf - SABINE Power-Q Operating Information Manual

Ken Newman's career as a sound engineer encompasses over 20 years of working for performers
such as Anita Baker, Barry Manilow, Chris Isaak, and many other artists who demand the best.
Like his clients, Ken demands the best from his equipment, and his years of experience using
Sabine ADF products have helped him earn ecstatic praise from performers and audience alike.
Barry Manilow calls Ken "the finest sound mixer I've ever worked with." Here are Ken's own
suggestions for using Sabine ADF equipment.
Ask concert-goers, "Was the sound good?" Chances are the average listener will base their
response on a couple of factors. If the system is free of feedback, and the vocals are audible,
most people regard this as "good sound," with little or no consideration of the tonal balance or
perspective of the mix. On the other hand, you could have the most happening mix in the world
going, and if for some reason there are occasional bursts of feedback, the distraction and un-
pleasant nature of the squeals will earn your mix a very negative review. Likewise, if the audience
members can't hear what the singer is saying between songs, or understand the lyrics because
you can't get enough gain before feedback, then your mix will also be considered "bad sound."
For many years, I used 1/3 octave graphic EQs to control feedback, but found this to be a compro-
mise. Feedback is a result of peaks in the frequency response of the microphone, the
electronics, the speaker system, and the room acoustics. These peaks are rather narrow, at least
compared to the filters in a graphic EQ, which are based on 1/3 octave CENTERS, but actually
are much wider than 1/3 octave (most often an octave wide). A graphic EQ's fixed-point, octave-
wide filters are too inexact and too global to carve out feedback without taking out a big chunk of
music in the same slice.
I was introduced to the Sabine line of "feedback eliminators" a few years ago when I was working
on Ann-Margret's stage show with my friend John Reed. He had found that the FBX-900 afforded
him a good deal more gain before feedback on Ann-Margret's mic than what he had been able to
attain manually in the past. And since she's a quiet singer, this was an important breakthrough.
Since then, Sabine has continued to improve their whole line of FBX products, and with the
introduction of the Sabine ADF (Adaptive Digital Filter) Workstations, the process of feedback
control and gain maximization has become a great deal easier, more accurate, and more effective.
Here's a step by step guide that I've developed for using the ADF units to help get the best mix
possible, full of clarity and free from feedback.
First, the ADF needs to have its system parameters set correctly. On the global parameters page,
I set "Threshold" to a high number, so that the unit is more sensitive to feedback because it
requires less harmonic content. Then I set "Persistence" to a low number, so that less time is
needed for the unit to detect feedback. I set "Bandwidth" to 1/10 octave (a good starting point)
and set "Maximum Cut" to 10 dB...so the most filtering that can occur is a very narrow 10dB cut.
Next, I begin the automatic "ringing out" of the PA (assuming the sound system is all setup and
tonally balanced), with the mic most likely to need the greatest gain positioned on stage. I set all
of the ADF filters to "P" (parametric) except one, which I set to "D" (dynamic FBX), so that it will
catch the first feedback. Then I boost the mic gain until it starts to actually feed back, and voila!
the ADF catches the feedback, and makes a cut (only as deep as necessary to eliminate feed-
back at that mic volume) at the EXACT frequency of the feedback with the filter I had set to "D." I
then back off the mic gain, switch the "D" filter to "P," and check the depth of the filter cut. If it's
deeper than 3-5 dB, I usually change it to 3 dB for starters.