Feedback Issues

[hemismith]

Despite best efforts at mic and speaker placement, I still have occasional feedback problems, and I sometimes just need to get more gain. I just do various school, church, wedding, and other events and each situation is different, sometimes with roving mics, and usually with very little or no rehearsal time. Sometimes I can identify the cause but can

[Mogwix]

Peavey's feedback ferret is nice, but expensive.

 

A graphic EQ is essential at controlling feedback. Get one with 31-bands, like a dbx 231 EQ. Getting used to finding the problem frequencies and cutting them doesn't take too long.

[alcohol]

My experience goes contrary to the aged ones here even though I'm probably older than they are, but the Feedback Ferret or the DBX work really well in my experience. I filter out a half dozen bands with these, then back down the appropriate faders (mains or monitors). I've used the 31 band graphic for decades. I think the 31 band graphic is too wide and in difficult situations attentuates so much that eliminating feedback in difficult situations often compromises the sound, moreso than the specialized feedback supressors, which filter narrower bands. You might want to use the graphic EQ to adjust overall EQ to taste, but I've experienced the supressors as doing a more effective and sonically pleasing job at arresting feedback. This runs against the conventional wisdom here, but then, I didn't take a kneejerk reaction against these machines. ;-)

 

If you have no one running sound during performances, which is my typical situation because I'm one of the musicians, then someone unexpectedly moves a mic and you hear the feedback coming, you'll be amazed and grateful when you hear the machine pull down the offending frequency without you lifting a finger. The technology has changed over the years. No reason to use old ways when new ways are better.

[Jess]

If you need "more gain", then get your band to play quieter. 99% "ALL" feedback is that the fold back is just workin to hard. Its the classic old analogy that if something can't be heard in the mix, the first reaction is to turn that particular instrument/vocal up, when really everything else should come down.

 

Jess

[agedhorse]

Yes, volume controls work in the down direction too.

 

If you don't have the experience or time to use an eq, then maybe a feedback eliminator would be a good choice. Not the best choice for someone who had other tools and skills available to them, but given the circumstances and especially the application, it's worth a try.

[alcohol]

I used to think like agedhorse above until I used the machines. I firmly believe even those guys who think they have the best experience could benefit from a feedback supressor. The only tool I know that does the same thing is a parametric eq and it doesn't do it automatically, as quickly or with the same efficiency. It's like an automatic transmission for feedback supression. Some guys like to use a manual shift, but why not free yourself up to do other things unless you get some kind of ego gratification for doing what a machine probably does much better, especially for small PA situations.

[hemismith]

Thanks everyone, great comments. Especially interesting about the volume -- last time the lead singer kept telling me to turn him up more and more, but indeed I think the real problem was that the bass player right behind him with his massive Vox box was too loud and overpowered everything.

[lifeloverwg]

I'm not sure from your post if you are using monitors or not, but I just picked up a used Peavey Q231FX off of Ebay for under $200 to put on our two monitor mixes. I already have a DBX 231 which I now will put on the IEM and FOH for easier tone adjustment than getting into the EQ page in the Driverack. I am running monitors from FOH and there are enough times that I can't really hear the the lower level feedback that sometimes crops up on stage as the night changes but there is just enough to be bothersome for the ladies. I am looking forward to having the FLS for the extra help in those on the fly situations.

 

We have a Driverack PA for our mains and I much prefer using its narrower automatic filters for FOH issues when we are in a small highly reflective space. In small bar/club world its rare for us to have any time to tune the system for the space and the Feedback control has generally worked pretty well when needed. Luckily we don't have much trouble with feedback as we don't run at very high levels. My only problem with the Driverack auto feedback function is that sometimes when we are louder than usual in a tough space it starts to think sustained notes on the guitar are feedback.

 

Winston

[alcohol]

If your mixer has inserts on subgroups you could have the driverack or feedback supressor on just vocals eliminating that sustained guitar note problem. You could also have a channel of an feedback supressor on an individual channel.

[agedhorse]

The (automatic) feedback eliminators do not necessicarily detect feedback accurately in that sometimes they are fooled into thinking something is feedback when it's not, especially when used in live mode with music. Using fixed filters will generally improve the performance of the detectors when used without background music signal confusing things, BUT with very narrow filters, moving the source a few feet can change the frequency enough to cause another problem.

 

Also, if a system itself contains gross response nonlinearities, narrow filters are about the worst choice for "fixing" the problem. The real source ofthe problem should be corrected first (be it crossover issues, speaker problems etc) before expecting good results with one of these "fix-it" units.

 

Ironically, these devices work the best (and quite well actually) on systems that are already nicely designed and implimented. These are the same systems that least need the help, but for specific peaks that may crop up due to mic placement geometry, it can be an ideal tool.

[alcohol]

The current generation of feedback supressors set the first half dozen or so offending frequencies. You set these with mics open and no one singing or playing. You then set the supressor for normal operation which then has the supressor acting as a fixed filter for those frequencies. It does this with a resolution that's sharper and more accurate than a 31 graphic eq. If you feed guitars through the PA system you might have a problem with guitar signal attenuation. But, you can set a feeback supressor in fixed mode so it doesn't use additional filters after the first half have been set up.

 

However, in many small situations, PAs are not used for instrument amplification. Feedback supressors are ideal for these situations.

[Jess]

Thanks everyone, great comments. Especially interesting about the volume -- last time the lead singer kept telling me to turn him up more and more, but indeed I think the real problem was that the bass player right behind him with his massive Vox box was too loud and overpowered everything.

 

Yup!......I work in a band that plays 3-4 nights a week and we "NEVER" have feedback probs from foldback because our foldback level "NEVER" moves. our foldback is set at a level that is loud enough to hear very well but is well under any feedback problems. As i said before, if your band has the discipline for everybody to stay at the same "stage level" night after night, then your foldback probs will cease to exist.

 

Jess.

[hemismith]

Thanks again. So I now realize that I should probably flatten the response of my monitors (Eon 10's) first.

 

The ideal processor I'd like to see for feedback would be a parametric EQ that sets up a filter if it thinks there is feedback but waits for you to hit OK before actually implementing the filter. Of course, as mentioned you can't hear minor feedback on stage from FOH, so it may require a signal from the band.

[JohnnyGraphic]

Here are some of my thoughts on all things feedback.

 

First off, lower overall stage volume is a great idea, but not always attainable (guitarists, drummers etc).

 

Proper room EQ is a must as is mic/speaker placement & good speakers/monitors.

 

Automatic feedback exterminators are great. The Sabine unit I had distorted easily and wasn't quite enough to do the trick. The dbx unit I have is great, but sets filters on the harmonica player. Also, some of the room ringing doesn't get caught for a while. Sometimes, the feedback will ring for a bit at a constant level. It won't catch it unless it gets much louder.

 

So, all in all, I like having it in my rack. I would be hard pressed to be without one. I haven't used the Peavey unit, but I'm tempted to see how well it works vs. my dbx unit. The Peavey EQ with FLS is also a cool idea and I like the lights. Also very cool.

 

A parametric might be more frustrating to use for feedback suppression than a 31 band EQ.

 

Johnny

[hemismith]

Interesting, great tips, thanks very much. I didn't want to bother everyone but was still stumped after all my research. You guys have given me some great new information; I really appreciate it.

[tlbonehead]

 

I used to think like agedhorse above until I used the machines. I firmly believe even those guys who think they have the best experience could benefit from a feedback supressor. The only tool I know that does the same thing is a parametric eq and it doesn't do it automatically, as quickly or with the same efficiency. It's like an automatic transmission for feedback supression. Some guys like to use a manual shift, but why not free yourself up to do other things unless you get some kind of ego gratification for doing what a machine probably does much better, especially for small PA situations.

 

Ya, solving a problem instead of trying to cover it up is only for ego gratification.

[tlbonehead]

The only one that I kinda like is the Roland AF-70. But it works differently than the other ones. It locks the frequency response in below feeback range and then keeps it there. That way you don't get any of those weird dropouts when the unit thinks it hears feedback.

[tlbonehead]

 

If you have no one running sound during performances, which is my typical situation because I'm one of the musicians, then someone unexpectedly moves a mic and you hear the feedback coming, you'll be amazed and grateful when you hear the machine pull down the offending frequency without you lifting a finger. The technology has changed over the years. No reason to use old ways when new ways are better.

 

My band does our sound from stage too with just over 9000 watts to the FOH and each onstage wedge getting about 200 watts. My 31 band monitor EQs are to my right on stage about 4' away from me. But it is very, very rare that I ever need to touch any sliders once we are dialed in and playing during the night. I mean very rare.

[alcohol]

 

The only one that I kinda like is the Roland AF-70. But it works differently than the other ones. It locks the frequency response in below feeback range and then keeps it there. That way you don't get any of those weird dropouts when the unit thinks it hears feedback.

 

 

Teh Peavey and the DBX can be set up to do the same.