Howling Feedback: A Thing of The Past

I'm sure there is not one soul on this planet that finds deafening and screeching feedback pleasing to the ear. And yet, most of us involved in the bowels of the music industry, playing small, pokey or intimate venues, have to with-stand this blood curdling noise most times we venture to play live.

I am here to tell you, promoter, sound engineer, musician, whoever...it doesn't have to be this way! Yes, i am a musician, though do not jump to conclusions. A musician telling an engineer how to do his job...blasphemy! And i would agree with you in most cases. However, we're all on the same side here: anti feedback. So, please indulge me for a moment, and take note of the following information that will save all of us, a hell of a lot of pain.

Feedback is an expression of a room's dimensions. One may note that not all feedback has the same frequency...this is because the dimensions of the room, determine which frequencies are amplified over the others. The way to combat feedback is to "tune" the room before any sound check commences...before any musician, bar steward, cleaner...anyone, enters the venue.

To tune the room, you will need a graphic equaliser inserted somewhere in the signal flow of the PA. Third Octave graphic equalisers are the best, because they have many frequencies with which you can boost or cut (they increment in third octaves from 20hz to 20khz). Even the most basic of PA's have some sort of graphic equaliser on them. Here is what you do with it:

1. Turn all the gain pots, eq, and master fader right down. Make sure the graphic eq is at zero on every frequency.

2. Plug a mic into a channel, put on a mic stand, place directly infront of a speaker, 1 metre back from it.

3. Now for the dangerous part! Set the gain on the channel the mic is plugged into, to about 3/4s. Now turn up the master fader very slowly. When you start to hear a bit of feedback, identify using your ears and brain what frequency the feedback is...this comes from experience. Pull down the frequency on the graphic eq until the feedback disappears. If you can't work out what the frequency is, try every one until the feedback abates.

4. Start to bring the master fader up until you hear feedback again. Identify the frequency and cut on the graphic eq.

5. Do this until the fader has reached maximum. The room will now be "tuned". The mic was pointed directly at the speaker because it was an extreme scenario. When you place the mic where you intend it to be onstage, it will be even less likely to feedback now. You will now be able to turn the PA up to its maximum volume without it feeding back. Efficiency!

Some individual EQing on each channel will affect your adjustments to the graphic eq, so this should be done reservedly. For example, if an instrument needs a little boost in the top end...think in the negative...roll off some bottom end, and turn the channel up...much safer!

If you have monitors, you will need to do something similar with them, preferably with a separate graphic equaliser.

Please spread the word that feedback does not have to be an essential part of live music. And please, do not take this as some self righteous rant against engineers...we're all pseudo sound engineers at some point of our lives...my only intention is to pass on some information that will save a few hairs on our cochleas.