Track21 Posted January 25, 2009 Share Posted January 25, 2009 I did sound at a function for Bristol City Council last night. The gig was held in the council building itself in a lovely long hall with stone walls, hard floors and a ceiling that just kept on going up! As you can imagine the acoustics were just fantastic for a 5 piece beach boys tribute band! ..... :) That wasn't the main problem however! They had an in house public address system with a total of 4 radio mics and a few small speakers dotted around the hall. Our system was completely separate from theirs and we were running our own Martin rig. When the event organisers wanted to make an announcement they planed on using the in house system. Unfortunately as soon as the mic was switched on we got loads of lovely feedback! After looking closer I realised the sound was coming from our rig! I ran to the desk and turned of all master sends for foldback and FoH, as well as muting all channels. Still got feedback. In the end the only way to stop the monitors whistling was to power them off! Even the keyboard amp was recieveing signal! I even tried turning the other 3 recievers off, and only leaving the microphone in question on. No joy! The show doesn't use any wireless equipment and I'm pretty sure there wasn't a hearing loop in the hall. Any suggestions on what could have caused this? The organisers just used our system in the end, and Im glad we discovered the problem before the doors opened, but still a pain in the ...... :P Link to comment Share on other sites More sharing options...
MarkPAman Posted January 25, 2009 Share Posted January 25, 2009 Probably there is a loop system installed, which some part of your system is picking up. I've been in a few situations where switching the loop off has been the only answer. Link to comment Share on other sites More sharing options...
Bobbsy Posted January 25, 2009 Share Posted January 25, 2009 First guess: a problem with the screen in one of your cables running to the monitors (powered speakers?) which turned it into a fairly effective tuning capacitor. The radio mic was near the monitor and was picked up clearly by said tuning cap. Any other guesses? Bob Link to comment Share on other sites More sharing options...
charlyfarly Posted January 25, 2009 Share Posted January 25, 2009 I would tentatively agree with Mark...induction loop. It can do some very strange things that you describe.Couple of years ago I did a gig in a beautiful municipal venue in Germany. Before soundcheck I kept hearing people who were talking on stage through any channel or bus PFL'd. Disconnected all inputs at the desk end...still the same. Even the backline was picking up talking. Bearing in mind that we were in mid tour carrying full production that had worked perfectly I was somewhat flummoxed. I asked the house technician, who was also the janitor and he said that there was an induction loop active throughout this particular hall. Turned it off and bingo! Link to comment Share on other sites More sharing options...
Track21 Posted January 26, 2009 Author Share Posted January 26, 2009 Cool, thanks for all your help. I'll head straight for the loop in future! Although I'll also be checking the screening on the monitor cables. They don't look particularly great! Link to comment Share on other sites More sharing options...
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