Feedback Prevention Method For KJs

Everybody has to deal with feedback in their karaoke DJ equipment sooner or later.  You won’t find a magic bullet for feedback, since the potential exists for it any time you have a speaker, mic, and amplifier.  Whenever some noise goes looping through your system at a given frequency there is feedback.  Looks as though a karaoke DJ deals with additional feedback problems because of the added variable of multiple wireless microphone signals and the necessity of adjusting microphone gains so often.

If wishes were horses, you could control the majority of feedback with ideal arrangement of your speakers and microphones.  In the real life of a mobile KJ, the acoustic qualities of your changing venues are a feedback wheel of fortune.  You get echoes, irritating standing waves, and the venue owner imposing contrary limitations on your rig.   How frequently will anybody set up – except in a studio – in a “perfect” acoustic venue?

The easy solution to feedback is using an auto-pinking unit like the dbx DriveRack PA and a calibration mic.  You could eliminate the graphic equalizer, limiter, feedback controller, and crossover and replace all those units with the DriveRack PA in a single slender rack slot.  Bad news, the six hundred dollar price tag is likely to crack your piggy bank a little.

Ringing the room is a less expensive, hands on method of preventing feedback.  As long as you have a decent graphic equalizer you’ll be able to ring the room.  It takes perhaps fifteen minutes to do once you have done it a few times, and it’s an effective way to prevent feedback as long as you make the small modifications for the acoustic variables between empty room and a room filled with bodies.

Half the battle is getting all your gear placed right to reduce feedback before you even begin the ring.  Next, power your amplifiers up, but keep the main gain all the way down.  Put all your equalizer sliders in the middle at “flat.”   If your VocoPro mixer has equalization controls, be certain these are set in the center, likewise.

Un-mute the main microphone and have someone start singing a stable song.  Feedback will occur at some point as you gradually turn up the system gain, so proceed slowly.  That first feedback loop is likely to happen at the peak frequency particular to your equipment or at the frequency that the given venue naturally resonates at.

Go to your equalizer controls and tune down the problem frequency.  Identify which frequency range is the problem by adjusting the sliders on the equalizer until you locate the correct one.  (Or get a spectrum analyzer that tells you which frequency is spiking.)  The best practice is to move the equalizer control down and then bring it as far back up as you can to a spot short of the feedback loop.  Doing that will minimize the distortion of the sound quality.

As you continue to turning up the gain you’ll discover more troublesome frequencies to tune out.  In a typical space, you may have to adjust up to eight bands.  When you keep ringing out the room past a certain point, you’ll either get :a whole bunch of frequencies shrieking; the already adjusted frequencies shrieking again as you increase the gain; or the quality of your sound gets really bad.  

The last step is to make a feedback safety margin by turning back the just achieved volume by eight to twelve decibel.  It may be possible to milk 5 or as much as ten dB more from your system with a careful ring.  You don’t want to push the gain at the cost of sound quality, though.  And you shouldn’t let any of your other volume controls in your machine karaoke set up creep up higher than that main gain setting you’ve just achieved.  I hope this method will prevent feedback the next time you set up.