Automatic Feedback Suppresors - do they really work?

[Rockin Mike]

I have this:
dbx AFS-224 (dual 24-channel feedback auto-suppression)
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It seem to work OK in the rehearsal room, but I haven't tested it at gig volume or in any other rooms.

Are auto-feedback suppressors like this effective in handling squeals live, or should I ditch it for a manual graphic EQ?

Thanks for your advice.

 

[T-Bird]

Hi.

IMLE they do work, but I for one have never felt the need to use one.

They can be beneficial if the source(s) is really difficult or if the venue is absolutely horrible acoustic-wise, but even then a good multi channel parametric EQ is more to my liking.

I wouldn't say a GEQ is better or worse, I use GEQ to equalise the room to the PA, not vice versa.
IOW, no ringing it for me.

Regards
Sam

 

[bigswifty1]

It depends on what's causing the feedback, but they -can- be spectacularly effective. I can't recall the brand or model that our BL in one band uses but it has totally transformed their live sound which always suffered from excessive stage volume (I know I know, I tried).

You put a mic in the centre of the venue, set it to automatic and generates a bunch of pink noise tones and you can actually hear it start to ring, then stop as it jumps on that frequency. When it's done you obviously remove that mic.

You can also save the eq profiles for the venue as a baseline for next time.

Mike

 

[Zooberwerx]

I used the DriveRack's auto EQ + pink noise to set FOH....about 2 years ago and haven't touched it since. The unit has FB suppression but keep in mind that monitors are more problematic.

Riis

 

[ThirstyMonkey]

I thinkk feedback suppressors are a great addition to a PA. When you're running sound from stage, which I do, it can add to your peace of mind. My band has two Behringer Feedback Destroyers for our four floor monitors. They work exactly as advertised. Unfortunately, we don't get to use them as at many gigs as I'd like. It turns out that customers in the bars we play get really annoyed if we try to properly run and to set up the notch filters. So instead, I have to go old school and focus on monitor placement/volume and EQing problematic freq. on the aux sends to keep feedback in check. So I guess my advice is, they work and our useful tools if you're actually going to be able to use them in the real world.

 

[Johnny Crab]

Do you think they(the Behringers) would work if you just walked in, set up, pushed AUTO, and started the show?
I get fdbk issues sometimes on a vocal mic via the BOSE when we're in a tight area and MANY times there is no time for a "real" soundcheck.

 

[modulusman]

Do you think they(the Behringers) would work if you just walked in, set up, pushed AUTO, and started the show?
I get fdbk issues sometimes on a vocal mic via the BOSE when we're in a tight area and MANY times there is no time for a "real" soundcheck.

I use to have a pair of Behringer feedback destroyer pro DSP1124Ps. They have different settings that made it possible to just plug and play. That is how we used them. Never worried about ringing out the system.

 

[Rockin Mike]

I wonder how they work if there are two feedback suppressors, i.e. one for the mains and one for the monitors...
Feedback works in a loop; speaker->airspace->microphone->electronics->back to speaker
Typically you have at least two loops, one for mains and one for monitors.
The mic and airspace are common elements in both loops, so if there's a frequency feeding back between the mic and the monitor, that sound will also come out the main speakers and bleed back into the mic from there. Probably not as bad as the monitors, but some.

I guess each suppressor would attenuate that frequency independently for each loop until it's down to an acceptable level in that loop...

 

[Rockin Mike]

I wonder what Jimi Hendrix would have said if an automatic feedback suppressor took his guitar out of the mains at Woodstock during "Star Spangled Banner".

 

[wemmick]

I have a Behringer Feedback Destroyer as well. In my experience, feedback through the mains is easier to control for with speaker placement. With monitors pointing up at a low ceiling on a bar stage, we've had a lot of success with using the Destroyer for the monitor mix only.

 

[jimfist]

I'm not a fan of suppressors. I don't enjoy what they do to tone.

...suggestions for minimizing stage feedback and optimizing performance:

- if possible, put your wedges on (tripod) stands, side-filled, and up at face level. Ditto for rear stage drummers, keyboardists
- if you can, employ wedges that exhibit the inherent DESIGN EQ characteristics for the job, and DON'T over-EQ them. Use a PARA EQ if you must. Stage wedges with a mid/upper midrange presence bump may not be great for FOH PA, necessarily, but just what is needed for stage monitors.
- less EQ allows the speakers to retain their openness of tone and clarity. You may be surprised that less EQ may translate into more clarity, when compared to the approach of "more VOLUME with feedback ferret filtering", of which I'm not a big fan.

All JMHO, and different strokes, etc. Of course, when it comes to vocalists and stage monitors, sh!t in = sh!t out, so it helps when singers have strong voices, good technique and good sounding mics designed with high signal-to-noise and feedback rejection in mind (Audix OM5, for example).

 

[shoot-r]

This is a interesting thread.

I may check into Behringer's Eurocom TN 6232 Feedback Destroyer for our monitors as we're trying to run our sound from the stage now-a-days.

It looks to be as KISS as you can get!

Has anyone worked with one of these?

 

[mfleming1963]

My band used to use the FBX 901 Feedback Eliminator on the vocal monitors. They allowed us to get more volume than we could get without using them. Additionally since we ran sound from stage, we could use it to kill unexpected feedback during performances. I wish they still made these units.

 

[Zephrant]

Anyone use the ones built in to the newer powered speakers like the Mackie SRM line?

 

[jsolberg]

I run sound from the stage. Had one of the Behringer Feedback Destroyers on the monitors. I felt that was very ineffective. I now have two dbx AFS-224's in the rack. I can't remember the last time I got feedback at a performance. I have them set up on channel inserts for the three vocal mics plus the acoustic guitar. I like that setup because it will catch feedback from any source. Have them set so they'll release the frequency after 10 minutes. I think they help and don't noticeably color the sound. I can't just crank it up carelessly, but in those situations when I'm on the edge it does help. When I take a look at it after a song ends there can be as many as ten frequencies lit up on the lead vocal channel.

 

[Rockin Mike]

That's what I have, the AFS-224s. What is the advantage of setting them up as channel inserts versus putting them inline between the board and the (powered) monitors?

 

[73jbass]

I had the DBX unit for about a month,then just learned to ring out the pa with the graphic eq,and thats all I needed.

 

[Rockin Mike]

Kind of hard to reach for the graphic EQ in the middle of a song.

 

[73jbass]

You ring out the pa before sound check.Mostly for the benefit of vocal monitors. For the monitors I rolled of everything below 100hz,a cut at 250 ,and another at around 2500. No feedback in the monitors ever.The mains I set by playing music and tweaked the eq until it sounded good. That simple. Once I got the eq set for mains and monitors,I rarely had to readjust it.

 

[Jazz Ad]

I have never used a feedback supressor, although I like the idea especially if they are dynamic.
I have a Behringer graphic EQ in my PA rack with a feedback detector led on each slider. I adjust levels before the show and kill feedback areas.
I very rarely have to do anything else afterwards.