At the Gig: Five Ways To Avoid FeedbackAugust 22, 2008 6:00 am Live Sound
One of the worst events that can befall a band during a show, aside from actual injury to any of its members, is to have a screeching blast of feedback suddenly deafen the audience, sending the band’s approval rating spiraling downward. If there is a sound man, he’ll probably get the blame, although as we’ll see, it might not be his fault!
Feedback can come through either the main speakers or the monitors, although in my experience it is more often the monitor speakers that feed back. (That way the band is briefly deafened too.) Usually, the microphones are behind the main speakers and the system isn’t running at the very edge of feeding back, but if these are not the case, you may be able to coax out some feedback from the mains as well as the monitors!
Back to basics for a mo: what is feedback, anyway? As the name implies, it results from speaker sound “feeding back” into (i.e. being heard by) one or more microphones that are running through that speaker. Round and round goes the sound. It’s like giving oats to a sick horse - you get the feed back. (I’ve been waiting to use that stupid joke since summer camp in 1962.) There are a number of steps that can be taken to minimize the possibility of this unfortunate menace. Here are five of them.
1. Minimize the number of microphones onstage.
If you can make a direct connection of some kind (DI box, amplifier output jack, etc.) to any or all of the instruments, do it. Each microphone you can eliminate from the stage is one fewer feedback source to plague you later. (See my article Use Direct Connections For Onstage Instruments for some tips on making these connections.)
2. Turn down any microphones that are not in use at the moment.
This is in keeping with the previous idea about minimizing the number of potential feedback-producing microphone-speaker loops. A microphone that is turned down all the way can’t feed back!
The fact is, I’m going to recommend that you don’t turn unused mikes all the way down - just halfway or so. This is so that when you forget that you are being careful about feedback and that you turned down the backup singer’s mike ten minutes ago and she suddenly starts singing, you (and the audience) will at least hear her to some degree before you manage to restore her level.
3. Don’t let the band move the microphones around.
This is one of the main causes of monitor-speaker feedback. It’s funny, but everything can be fine, then the lead singer moves his mike two feet to the left and shortly thereafter it starts feeding back. The pattern of locations that do and do not produce feedback onstage is very complex. Once you find a microphone placement that works, try not to change it much.
If your singer is a flamboyant, Roger Daltrey type who needs some elbow room, be sure you have checked the setup out in advance (at full volume) to isolate any “hot spots” that may cause feedback. (You can mark these areas with tape.)
4. Don’t operate at the edge of feedback.
If you have the main or monitor speakers turned up so loud that the system is perpetually just about to feed back, there’s something wrong with your setup. You can tell you’re in this situation if there are tiny hints of tones or “notes” heard when someone talks through one of the mikes. Those tones are micro-bursts of feedback!
You don’t have to be that close to the edge to have problems, though. Operating anywhere near the feedback point cuts your margin of error and makes it more likely that one of the factors mentioned earlier will kick in, and then there goes your reputation. Back off on the gain levels and sing louder or get closer to the mikes. Or, put up with sounding a bit quieter in the room. It’s better than feedback!
5. Watch out for instrument feedback.
I’ve been talking about microphone feedback here, but electric guitars are notorious for “string feedback.” This occurs when the amp speaker sets the guitar strings to vibrating, and then that note comes out of the amp speaker, which sets the strings to vibrating even more, which - well, round and round you go again.
If this happens while playing, the hand-on-the-strings method can be used (unless you want the feedback, Jimi). More common is for the guitar player to put the guitar on a stand right in front of the amp, resulting in louder and louder string feedback. The best way to avoid this is to get in the habit of turning the volume knob(s) on the guitar all the way down before putting the guitar down. Just don’t forget to turn it back up!Tags: microphones, mixing, stage practice -->