Massive feedback in our practice hall

Hi this one may be a bit vague to get a solution for but i thought id give you all a try and see what advice those with the experience could give. Me and my band have ust arranged to use the local colleges massive lecture / drama theatre / hall for practices once a week. We turned up for the second week last night ( i wasnt there last week nor was the other guitarist) and we realised we have a massive problem with feedback.

basically even with the amps turned right down as soon as they were turned on we got really bad feedback from both. The amps were at opposite sides of the room about 20 meters appart. we tried moving the amps around to no avail. The room has its own small pa system - 4 smallish peavey speakers and a microphone on the lectern at the front. we unplugged all of this and it didnt help. The room is about 20m across by aporox 30/ 35 meters long i think. the ceiling slopes along the lengh of the room at maybe 20 degrees and at the lowest point is proberbly 4 or 5 meters high. Ive been playing a while and had feeback before due to proximity to the amps etc and is normally easy to solve

this was different - ddnt matter where you stood we got masssive amounts of feedback all of the time which meant we couldnt practice. we really like this hall and want to keep using it but un;less we solve the feedback problem we wont be able to.

The two guitarists use marshalls - i have a mode 4 and he has an AVT 150 or something. both go through marshall 4 x 12" cabs. The guitars being used were a strat copy ('legend'), and my 1973 fender strat. we also tried using two guitars with humbuckers wondering if this would make life better - we tried a gibson ES335 and an ibanez RG570EX. the problem was slightly better but still bad enough to prevent us practicing. The bss player and keyboard player had no problems - bass player through a peavey TKO115 bass amp with external peavey cabinet and using a peavey dynabass international series bass with what we think are passive dual coil pickups. tried the guitar through the keyboard amp briefly at low level and got masive feedback. but it cant be the guitars sureley? strats get used all the time on stage - i know singtle coils can be a pain in the arse but they cant be this bad can they?

Theres a huge silver metal (aluminium?) frame throughout most of the room with lights etc suspended from it. it extends over about half of the rooms area. moving to the end of the room away from this rig helped slightly also.. but didnt solve the problem enough to practice. could this rig be the problem? we thought about this but then thought hang on, lots of stages at gigs have that kind of thing for the lights etc with no probs.

is there any simple solution to feedback problems? how does feedback occur? any advice that will help us find out what the problem is and maybe elliminate it would be REALLY great - im off to look around on the net now for some details of what feedback is how it occurs etc but so far ive found not a lot....

Many thanks!!

Have you tried moving around yourself? In stead of standing in front of the amp, try stand next to it...

Does the room happen to have smooth & solid(concrete, glass,...) surfaces on the floor, ceiling and walls? It sounds to me like the room in which you're practising might just be an acoustic nightmare(too many reflections). If this is actually the case, you might want to look for another place to practise.

Originally posted by Tweak
how does feedback occur?

Feedback occurs when the signal coming from the amp gets picked up by the pickups in your guitar. Normally this should only occur when you're standing directly in front of the drivers. In a room with highly reflective surfaces, more signal coming from the amp indirectly will reach your pickups, making it harder to control the feedback.

Anyway, that's just my 2 cents...

[Edited by SPL on 10-25-2003 at 08:44 PM]

Many thanks for replying...

we tried moving around all over the place to no avail - wherever we stood the feedback came back - there were a couple of very small positions where the feedback disapeared but they were so small, and hard to find spots that if you turned around even slightly or stepped on a pedal, or took a step in any direction the feedback came straight back. Cheers for the advice. Any ideas why the bass didnt have so much trouble? Proberby down to low frequencies not reflecting well / being absorbed etc or something along those lines i would guess...

Anyway thanks again.. I was wondering about one of these feedback busting devices - feedback ferret 2 or something.. but the feedback was so extreme that i would guess something like that wouldnt be up to the job

SPL is spot on, you want to put as much distance between the guitars and the amps they are plugged into as possible. Never let the guitars face the amps. Also, avoid hollow body guitars !!!!

Try turning your guitars down when you are not playing (using the volume pot on the guitar). This may not do much for your long sustained notes but it will be better than defining people. If you are using an LP type guitar you can set the vol to "0" on the pickup you are not using and use the PU selecter switch as a kill switch, turning everything off instantly. You can also buy cable with a kill switch built into it.

If this don't work then you can solve the problem with either a gate (expander) or a feedback destroyer. You can pick up a second hand Behringer noise gate for about 20-60 bucks on eBay.

Remember what feedback is, it is the guitar picking up signal from the amp feeding back to the amp being picked up by the guitar.

Break the loop you solve the problem (Oh how very Zen of me !!!).

G'luck dude !

[Edited by Dr_simon on 10-25-2003 at 08:07 PM]

Originally posted by Tweak
Any ideas why the bass didnt have so much trouble? Proberby down to low frequencies not reflecting well / being absorbed etc or something along those lines i would guess...

Low frequencies actually reflect a lot easier than high frequency waves.
The reason the bass guitar doesn't have any problems with feedback is because of the long wavelength of the frequencies produced by the bass. High frequencies(very short wavelengths) cause feedback a lot easier.

A couple of years ago, my band played in a gynasium and we sounded horrible due to the same problem your having. A few years later and a new band, we got asked to play another gymnasium show. Of course I was very hestitate but the other guys convinced me it was a show and we shouldn't miss it. Plus it was an important show for the other band which asked us to play. Back to the story, well we set up and started playing and to my surprise no feedback and we ended up sounding great that night. I actually got a chance to talk to the guy who was running the sound that night and asked him what he did. Here's what he said the answer would be.

Since you have a PA at your disposal, try micing your amp through the PA system with a uni-directional mic (shure sm57). This will hopefully break the feedback loop. You shouldn't have to turn up your amp much, just enough to were you get a strong signal on your mixer. If feedback occurs before you reach this peak, try throwing a light blanket over the front of your amp and the mic. Ok once that is solved, place the PA speaker in front of the space where you guys stand. Face them about a 35' to 45' degree angle away so that you can't see the front of the speaker from where you stand. This should solve the feedback problem, but you'll still need to follow the advice of Doc and SPL.

If this does not work, it's definitely the room and you'll just have to find a better place. Sorry. Look for something that doesn't have alot of metal surfaces. Concrete is ok, but wood, and dry wall are the best because they all can absorb some of the sound waves. Also if you can carpet the floor that will help with absorbing soundwaves. You need to find a better acoustical environment. Good Luck!

[Edited by noticingthemistake on 10-26-2003 at 11:16 AM]

There's an acoustic kit I bought last time I was in England so I don't know if they're available here
called 'PrimAcoustics' . It basically consists of kits ranging in price from a coupla hundred to a coupla thousand pounds depending on the room size. They're preshaped acoustic foam 'blocks' that you attach to the wall with either a glue gun or if you wanna move em around use velcro. You don't cover the entire wall...just sorta place them in areas where sound is getting badly reflected. You can cut em to size too if ya want.
As soon as I put em up I noticed a huge difference in sound quality. All that high end metalic ping sound had disappeared and on the playback monitors, all the bass tightened right up.
Best thing is you can keep a small 6' X 3' kit in your car and put em up temporarily when you need em.

Just a quick question for some of the more experienced cool edit cats out there .I am now planning to record my mix cds via cool edit istead of my boss br 352. All i need to no is can i put increments in my mixes,so when i burn it in nero to cd its not just one long mix and you can flick through the tracks? I know this is an easy one to most of you out there,i would be grateful for any help!! Many thanx Cutloose

A very simple fix is to insert 2-5 seconds of silence at the beginning of the song (using the Boss recorder). I don't know this bit of kit inside out however this kind of utility is normally found under a Track edit menu.

Yeah on Cool Edit, to put in a bit of silence just go to "Generate", and "silence". Make sure your marker on the audio is at the beginning, you don't want to put the silence in the middle of the tune. ;) You can also do this on Nero, I believe it's once you drag a track over. Highlight it and there should be a option to insert silence. Also your going to want to record each song/track seperately. Don't record the whole CD or whatever as one audio file. Record each track and save it, then place them together in Nero, so you have a track list. I know you probably know this but from your post I wasn't sure. Have fun!