Church Audio – Killing Feedback

As I thought more about my last post which talked about Church Audio Problems, I thought I’d continue my church audio blogging by talking about a problem that has plagued churches across the country regardless of denomination or beliefs.

If you have run sound for any length of time, you have probably heard feedback

.  And if you haven’t, I’m sure you will in the future.  It can come in the form of a low rumble, a mid range “yaaaaa” sound, or a hit whistle that makes everyone want to duck for cover.  (Believe me, I’ve seen it!)  Feedback can be difficult to find and control because it can take different forms and be caused by different problems.

First things first, we need to understand what exactly feedback is and by doing so, we can figure out what causes it.

Feedback is the result of sound being cycled and recycled through the sound system.  Let me explain what I mean.  What happens during feedback, is that a microphone receives and amplifies sound that has come out of the speakers.  The microphone sends that sound back through the mixing console to be once again amplified by the speakers creating what is known as a “feedback loop”.  This can increase exponentially and instantaneously resulting in and undesirable sound we know as feedback.

Now that we know what feedback is, we can dive into how it happens and figure out how to prevent it.  The best way to prevent feedback is to stop it before it starts.  Sometimes, it can be from a vocalist cupping a microphone, letting the mic hang at their sides, pointing the microphone towards a speaker or monitor or from improper gain structure, EQ, or processing.  Let’s talk through some steps to prevent these issues.

STEP NUMBER 1: PROPERLY EQ YOUR SYSTEM

First and foremost, your sound system must have a graphic system equalizer.  If you don’t have one, you should probably consider investing in one.  What this allows you to do is equalize, or tune your sound system by using a series of frequency filters to adjust the intensity level of different frequencies.  Spikes in specific frequencies can be caused by speaker positioning, room acoustics, or various other factors so I would seriously recommend hiring a trained professional to take care EQ’ing your system for you.  That way you can be sure you’ve got everything set properly and know nothing will be damaged due to improper system setup.  However, it is possible for you to do this yourself using a spectrum analyzer connected to an RTA mic.  A spectrum analyzer can play reference audio through your system and the RTA mic will sense which frequencies are louder or softer then others and display them on the screen of the spectrum analyzer.  This will tell you what frequencies you need to boost or cut (increase or decrease) on your system graphic equalizer.  Once you get your system equalized, it will give you a good starting place and a “clean plate” to start working with.

STEP NUMBER 2: PROPERLY SET UP YOUR STAGE

When setting up your stage, make sure that your monitors are positioned correctly and that your microphones are set up far enough away from the main speakers that they won’t cause issues when you begin mixing.  Also, talking to your worship team, worship leader, pastor, or anyone else using microphones, and instructing them on proper usage is always very helpful.  Make sure that singers hold microphones close to their mouths when they are singing.  If they are not singing, ask them to hold the microphone, facing upward, in the middle of their chest or stomach

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