We have a practice space it a rectangular shape room. it's about 12x20. the drums are in the corner. a bass amp and guitar amp are along one wall, and the other guitar amp is on the other wall. we have the speakers on the wall oppisite the drums (imagine the drums and speakers are facing each other across the room). we use a mackie 808m mixer and 2 JBL speaker cabinets with 2 15" speakers in them. it seems like any time we get the vocals to a level that we can actually all hear them, the PA starts feeding back alot. we don't have the mics (cardiod dynamic) facing so they are getting the output from the PA back into the mic, they are facing the opposite way actually. any ideas on how to fix this??
feedback problem with live PA, how can i stop this??
- Thread starter ralf
- Start date
Treeline
New member
You have a twitchy situation no matter what, but you really need to get a graphic equalizer. Do a search here and on google for variants of "sounding a room" and you should pick up a lot of material. The basic idea is to isolate the room's most resonant frequencies and then cut those bands using the graphic EQ. You find the frequencies by cranking up the gain with all the mics on until it begins to feed back. Back off the gain just a bit and then start playing with the EQ's faders - boosting each in sequence until you find the hot one. Then cut it a bit, raise the gain some and then do it all again. You may find hot spots at 1 and 4 kHz first. After you do this a few times in succession, you should have better luck hearing yourselves without feedback.
I have one like the pic and it works. Cost me less than a hundred bucks.
I have one like the pic and it works. Cost me less than a hundred bucks.
Attachments
MessianicDreams
New member
also try cutting some of the highs out, if you're not going to purchase a graphic.
cusebassman
Freakin' sweet
This is a slightly more expensive route than trying to notch out the frequencies that are causing the feedback, but is quite effective... pick up some hypercardiod mics. This won't solve all your problems, but helped me with some major PA issues this last month. I am putting on a show (this weekend, actually!) in a rectangular firehall with a stage set into the center of one of the long walls, and the PA cabs are facing away from us (which is the first step to removing feedback, but you don't have that option), and since I am recording it, I am using condensers for the vocals. This obviously creates a major feedback issue, but I much prefer the sound of condensers to dynamics in a recording setting, so standards be damned! I picked up two Rode NT3s on ebay for half price, and they work wonders. You have to be singing right into the front of those things, right up close for them to grab any sort of sound. Not the best for studio recording, solely because of how close you have to get to them, but for live recording, they are great, and they eliminate most of my feedback issues... I plugged one in, ran up in front of one of my 1x15" cabs, and from two feet away it wasnt feeding back, and the sound was filling the room. Just my humble suggestion, but this may be the way to go (bare in mind, however, that with condensers comes the need fort phantom power - you might want to poke around for some hypercard dynamics, if they make such a thing... time for some research, cus now Im curious!)
Another thing you could try for practice purposes is getting a headphone amp, attaching it to the output of the board (send a separate mix through aux outs if you have em, or just run the main outs to the thing), and give people earbuds or headphones for practices. I know headphones are rather a cumbersome annoyance when you are just playin live, but this may be another viable option in such a tight space.
Another thing you could try for practice purposes is getting a headphone amp, attaching it to the output of the board (send a separate mix through aux outs if you have em, or just run the main outs to the thing), and give people earbuds or headphones for practices. I know headphones are rather a cumbersome annoyance when you are just playin live, but this may be another viable option in such a tight space.
A couple other thoughts-
In those type of situations, you have to stay right on the mic and learn to project. In a room that small, if you are a few inches off the mic and singing quietly the odds of getting enough GBF (gain before feedback) to compete with a drumset are slim in any case. And everything nearbyby bleeds into the mic, and competes with your voice. You get into a situation where say the snare is as loud as your voice in the mic, and goes through the PA, and then you turn the mic up because now the snare is louder, which makes your voice louder, but the snare gets louder too and on and on and on.....
Make sure the speakers are high enough to put the horns around ear level. And your amps are placed so that the players can play at reasonable volumes
. If you have to crank your amp to hear it because it's shooting at your knees or you stand right next to the cymbals, you should change that. Tilting an amp so it shoots at your ears makes a lot of difference.
Keep the mics flat. By that I mean parallel to the floor. A cardioid's null spot is directly behind it. Tilting it up makes it more vulnerable to sound reflections coming off the ceiling or shooting at the mic from the PA in your case.
In those type of situations, you have to stay right on the mic and learn to project. In a room that small, if you are a few inches off the mic and singing quietly the odds of getting enough GBF (gain before feedback) to compete with a drumset are slim in any case. And everything nearbyby bleeds into the mic, and competes with your voice. You get into a situation where say the snare is as loud as your voice in the mic, and goes through the PA, and then you turn the mic up because now the snare is louder, which makes your voice louder, but the snare gets louder too and on and on and on.....
Make sure the speakers are high enough to put the horns around ear level. And your amps are placed so that the players can play at reasonable volumes
. If you have to crank your amp to hear it because it's shooting at your knees or you stand right next to the cymbals, you should change that. Tilting an amp so it shoots at your ears makes a lot of difference.Keep the mics flat. By that I mean parallel to the floor. A cardioid's null spot is directly behind it. Tilting it up makes it more vulnerable to sound reflections coming off the ceiling or shooting at the mic from the PA in your case.
How reflective is the room? Even if there's no direct path from speaker dispersion pattern to mic polar pattern, if the room surfaces are very reflective you can still have feedback issues. You may actually do better to point the cabs across the mics rather than bouncing the sound off a close back wall and into them. Think about how the sound reflects to the mics as if the walls were mirrors and the speakers were spotlights. Avoid direct reflection paths, and get some absorption into the room.
FALKEN
*************************
to whoever negged me "don't be dumb" I was actually going to say that wearing earplugs helps me hear the PA better. also when the PA is feedbacking sometimes it means the instrument amps are too loud. also choice in mics and number of them could make a difference. was only trying to help the poster track down his problem, without speculating a hundred different things. thanks, though. you're really cool.
travelin travis
New member
i'm with treeline - use a graphic eq. also, i doubt that you really need two speakers in that room. more mics, more speakers, or both = more feedback.
JoeBannon
New member
The first thing that you should do is move the mic around to find out where it is most prone and less prone to feeding back. Second, sing loud. This will help much more than any graphic EQ'ing. The better signal to noise ration that you have, the less feedback. As far as switching to a super cardiod mic, this is a bit of a myth as far as feedback goes. Mics like a beta 58 pick up just as much stuff as an sm58, just that some of it comes from a different direction. Vocal mics like a beta 58 do not have as wide a pick up pattern in the front, but also have a rear lobe that pics up sound from the rear which can end up making things even worse. Not to mention that most feedback situations are not happening because of those few extra degrees of pick up pattern.
Sop what frequencies is your PA feeding back at? Are you getting a 200 hz rumble? A 1k squawk? A 6k squeal? These types of things have different causes and the problem may be pretty simple, or it may be somewhat complicated. Using a graph to help eliminate feedback will certainly help, but there will come a point with a graphic EQ where you are forced to make a real trade between volume and quality.
Sop what frequencies is your PA feeding back at? Are you getting a 200 hz rumble? A 1k squawk? A 6k squeal? These types of things have different causes and the problem may be pretty simple, or it may be somewhat complicated. Using a graph to help eliminate feedback will certainly help, but there will come a point with a graphic EQ where you are forced to make a real trade between volume and quality.