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How To Get Rid Of Feedback From a Live Sound System
How To Eliminate Feedback
Feedback is really annoying! It's one of those things that happens & most good sound engineers don't really want it! I work for a London sound hire company and I regularly have to eliminate feedback. In this hub we are going to look at my top tips on getting rid of feedback from a live sound system. I am going to concentrate on issues that happen in small venues, as I assume that is where most readers will be working!
My number one tip is to go out and buy a graphic equalizer. I am going to assume most readers are on a tight budget with a small system, trust me when i say this is the only tip that will cost any money.
The process explained below is usually referred to as 'ringing out the room/system'.
What you do is set up your sound system as normal, set-up one microphone to start with, turn up the gain a little more than normal and then turn up the master fader slowly until you get to the point at which you start to hear the ringing of feedback.
TOP TIP - Do this in a silent room, so no bands 'warming up'.
The trick is to turn it up so slowly that there is only one frequency feeding back. Balance it so that it isn't getting any louder or quieter. From there, you need to have a guess at what frequency you can hear. High frequencies are to the right of the graphic EQ, low frequencies are towards the left. Turn down (or cut as it's known in the industry) one fader. If the feedback doesn't go away, you are no where near. Turn the fader back up and try one three to the left or three to the right until you notice a difference. From there you can fine tune it by seeing which fader that is close by has the best effect on the feedback. The trick is to get rid of the feedback by cutting a fader by the smallest amount, usually a couple of dB will do it.
TOP TIP - Having said that, i would usually cut the first two frequencies you hear by 6dB (usually around half way down). Because they are usually the most troublesome.
For those on a tight budget, I would buy a Behringer FGQ. These little beauties light up the fader that has the ringing frequency! Which makes it really easy to do what I just explained! If you are in Europe, buy one from Thomann here. If you are anywhere else, use the Amazon link on the screen above.
After finding and eliminating your first frequency, repeat the process by turning the microphone channel up a little more! Repeat until the microphone is loud enough to be heard with out it feeding back
This tip is tough so don't despair if it takes months to successfully guess where those pesky frequencies are! Once you have mastered what I described above, you should start to develop your own techniques on developing this simple idea to work for you and your system.
- Dave Rat - YouTube
Lots of great advice. Some of it might be more advanced than what you need but well worth checking out.
Great Book That Is Perfect For Beginners
Tip number two, is allot simpler. As I said, I guess you are in small venues on small systems. If you are having issues with feedback from the main speakers, try and move them further away from the microphones. It sounds obvious but its a really simple trick that most people don't think about. The only issue is that moving your speakers further apart means you loose quality of sound directly in front of the stage so its a fine balance between the two (If you need sound directly in front of the stage that is.)
Tip Three - Heard of the 3 to 1 rule? If not, look it up! Basically, the further away you can get your main vocal microphones from each other, the more you can eliminate feedback.
Tip Four - If you have a problem with monitor feedback, (apart from using your graphic in tip one) a good tip to eliminate this is check what polar pattern your microphone has. This is basically the places the microphone picks up sound from. Check this article on polar patterns to find out more. If your microphone is a cardioid then its a good idea to have the monitor dirctly behind, because this is the point at which the microphone picks up the least amount of sound. If you have a hyper cardioid, then aiming the monitor slighting from the side is a good idea because this is where it picks up the least amount of sound!
Tip Five - Time for some serious shizzle. If you have a nice desk to play with and it has a phase button (Sometimes called polarity) on it (Looks like a zero with a line through it), you can get rid of some feedback using this great tip from Dave Rat. Check out the video below.