Thursday, May 27, 2010

The Problem with Any Feedback Destroyer

Let me just say that I think that some sort of feedback controller is an indispensable part of any mobile DJ rig.

When you are playing at five or more different venues every week, you'll run yourself ragged trying to adjust your 31 band equalizer by hand with each set up of your karaoke DJ equipment. Even keeping a record of the rung out equalizer won't really help, because humidity and the number of bodies in the room and gees, the phase of the moon all screw with the way sound travels through a given room.

Although ringing out each venue and then taking a photo of the equalizer so you've got a starting point every time you set up is a pretty good idea. (It's what I'd do if I didn't love the DriveRack PA that let's me auto-pink any room.) Especially since you can probably use your cell phone to take the picture and then store it on your DJ laptop, ha.

It's not like the old days where you had to get film developed and carry around a pile of prints. And then someone uses the photos as a coaster and you've got to dig up the negative... Technology is the DJ's friend, I say. Hurrah for digital images!

But the best efforts to ring out your venue and record those settings aren't going to cut it when you are looking to control feedback 100%. You'll want some sort of unit that automatically filters feedback. For karaoke DJs the challenge is even bigger, since you are likely to be dealing with a whole set of wireless microphones. And while those wireless VocoPro mics are terrific, it is getting harder and harder to find a no-interference frequency to get a clean signal. With the new FCC rules about which UHF frequencies you can legally use, that's going to restrict your ability to jump away from a problem microphone range even more.

Plus wireless mics cut your singers free from the cord...we've all seen those gypsy singers that wander around the bar without a care to the location of the speakers and how they are pointing the microphone directly into them. Sigh. Regular old unidirectional wired karaoke microphones are sometimes a blessing.

All this to say, you need a feedback destroyer if you want to run karaoke shows in multiple venues. Whether you like the Behringer Ultragraph, Peavey Feedback Ferret, or the granddaddy of all feedback controllers the dbx DriveRack PA, there is one problem with any feedback control unit: Every time a feedback unit inserts a notch filter into another particular frequency it will alter the sound output of your system.

True, most of these alterations are so minor that you'd have to be the world's biggest audiophile to hear them. (Doesn't that describe every DJ you've ever met, though?) Taken individually, I wonder if there is one ear in a million that could detect the presence of a single notch filter. But since most rooms have 6 or 8 problem feedback frequencies and those frequencies are generally scattered across the lows mids and highs, there can be an audible change in your sound. And if you've got a room that's a feedback misery, the automatic feedback units are going to jam so many notch filters in that your sound could be distorted enough that ANYONE might notice.

So, when you are looking at a feedback unit, make sure the notch filters are as narrow as can be. That's why I like the DriveRack PA - really narrow notch filters. The narrower the angle of the notch filter, the smaller the distortion of your sound is going to be. Plus, I love pointing the calibration microphone around. Makes me feel like Star Trek technology has arrived at last.

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