Avoiding Microphone Feedback

You should be able to EQ the feedback out of the vocals. Make sure the speakers are far enough away from the mic and not facing it. Just keep playing with the EQ and you should be fine. There are a ton of factors that can lead to feedback but EQing it should eliminate most of it, good luck.

 

Also, there are feedback destroyers available. Behringer Shark comes to mind, it's a small box with mic pre/feedback destroyer/something-and-other combined and costs around 100€.

I've been craving for one since the place we rehearse in has severe feedback problems with the room and the vocals setup.

 

Hi Wulf,

What about monitors? They're a common source of feedback if you don't have them set correctly in relation to the mics.

Make sure you use directional mics for vocals and instruments. Cardioid mics are good for miking the backline, but for vocals and frontline instruments, hyper- or super-cardioid is usually better because the null isn't 180 degrees off-axis, but more like 120 to 140. That helps put the null more in line with the monitor wedges.

Make sure the main loudspeakers are downstage of the band. Make sure that no mics point toward them.

It's often helpful when playing live to cut the 200 to 250 Hz region somewhat in your EQ to help counteract the natural boost you get in those frequencies from floor bounce.

 

Hi Wulf,

Okay, I wasn't aware it was a rehearsal studio. You said the loudspeakers are pointed toward the middle of the room. Where is the band in relation to the middle of the room?

The 200-250 Hz cut should be in the system EQ.

 

I find that in my basement, there tends to be some high end feedback. I cut out 4K and 8K a bit and it works like a charm.

 

As a sometimes sound guy, I can tell you there are 1000 different reasons why you're getting feedback. I'm not going to go into the reasons because the answer is always the same - eliminate the offending frequencies. Best way to do that is with EQ. There isn't a professional PA out there that doesn't have a 15 or 31 band eq on each foldback send that's primary job is to cut problem frequencies.

As for lugging gear, that Behringer shark device is tiny. I mean really tiny. From memory you need 8 of them to fill a single rack space. A nice 31 band EQ is only 1 rack space. Both weigh next to nothing.

The problem here is that these devices must be fed a signal that's before the amplifier - and some rehearsal studios use those powered mixers. so there's nowhere practical to insert them into the chain where thay can catch all the mics.

 

We added the Peavey Feedback Ferrett to our system a couple months ago. Absolutely no feedback from our monitors anymore. We can turn the monitors wide open now if we want to. We have the one for monitors and mains but so far we haven't needed to patch the mains in. I would have to say this is the hardest working piece of equipment you can put in your system. It reads the frequency that is feeding back and adjusts it without changing the way your monitors or mains sound.

 

Your positioning looks fine. It's pretty much how I would recommend it.

Here's a little EQ tip. Sometimes when you get problems in octaves as you did with 4k and 8k, it can be the octave one lower sending them off. So even thought 2k itself isn't feeding, it could be triggering the feedback at 4 and 8k. This doesn't always work but try cutting a bit of 2k and see if it helps settle 4 and 8. If so, you may even be able to put some 4 and 8 back in.

 

All you need is a graphic eq. To tune the PA to the room:
Reset the graphic so the faders are back to zero.
Take the main vocal mic and point it directly at the speaker where you would be standing when you are singing.
Goto the mixer and turn up the fader until the pa starts to take off.
This is the tricky part.
Find the frequency ton the graphic and pull it down till it stops feeding back.
Keep turning it up and taking out frequencies until you get the volume you want.
Simple.