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!!