Feedback is every live audio engineer’s worst nightmare, and it goes without saying that nobody in the crowd deserves to be subjected to an ear canal torture session. It’s your job as an engineer to ensure that never happens, so without further ado – here are 3 great strategies to help minimise stage feedback during a live performance.
Position your microphones (and vocalists) correctly
Ensure that you’ve correctly positioned your microphones in accordance to their given polar patterns. They should be relatively close to the sound source, and their polar patterns should pick up as little bleed as possible from other instruments. For example, a cardioid pattern picks up very little from behind the mic. Carefully plan out which microphones you’re going to use, bearing in mind their polar patterns will affect the amount of microphone bleed (and consequently – feedback). Vocalists should be positioned as close to the foldbacks as possible. Careful not to overdo it and give them too much gain or their microphones will run the risk of producing feedback.
Mute unused microphones when not in use
Muting unused microphones will help you to reduce the overall amount of pickup from the foldbacks and stage, allowing you to push the other mics a bit louder. If the band’s not using it – mute it!
Set your gains properly
It’s important to maximise your signal-to-noise ratio so that your performers sound big and loud without the irritating line/noise interference. Be careful though – pushing your channel gains too far may increase your chances of feedback occurring.
To find the right gain setting for every gig, many engineers use the “gain before feedback method”. With the fader at zero, turn up the gain carefully until you notice feedback. Immediately turn it down until it stops. Back it off just a little more, and you should be in the ballpark for a reasonably loud sound and have a good gauge of how much you’re able to push the channel before it begins to feedback.
A final note
More often than not, the cause of your feedback could be a few things. With experience, you’ll be able to pick out the issue and deal with it in a timely manner. Most importantly, it comes down to keeping an eye on your microphone positions, monitoring, and gain settings. Remember not to rush it, and make it your priority to getting that FOH mix sounding tight before anything else!