Controlling feedback. Sounds like something that our politicians in Washington do all day long instead of actually getting some kind (any kind) of legislation passed, doesn’t it? That’s as far as I will go into political commentary.
But, just like listening to politicians, feedback that comes through the sound system is painful to listen to, sometimes physically painful! Feedback (in our context) is that high pitched squeal or low rumble that you hear when the amplified sound is picked up by a mike or instrument pickup and put back into the sound system.
Now, you can buy a piece of equipment called a “feedback eliminator” which will supposedly remove all feedback from your system. However, I am not going to discuss using that piece of equipment for the following reasons:
- I have never used one before and therefore I can’t really say how effective they are in practice (nor can I describe how to use one).
- Most of the people who are reading this will never have the budget to purchase this equipment.
- You can easily remove feedback without one.
Causes of Feedback
First, let’s talk about the cause of Feedback.
As described above, feedback is due to amplified sound being picked up by a mic or instrument pickup. This usually happens due to the following reasons:
- Poor mic (or instrument pickup) placement – In a permanent sound installation (typical in a church), this is usually due to someone holding a mic getting in front of the main speakers or in some way not having the microphone in the location that it normally is. I once had a singer who made it standard practice to point his mic directly at the monitor speakers. We eventually shot him (just kidding).
- Sound Turned up louder than normal – If the sound is turned up louder than normal, the mic will begin to pick up the frequency that is most prominent in the room. When this occurs, you can hear the feedback starting and then backing off … usually as the person who is speaking (or singing) talks (or sings). The system is right at the edge of feedback.
Remedies for Feedback
In either of these cases, having the feedback come through the mains is unpleasant and sometimes painful. So we have to fix the problem. We do so in the following way:
- Check to see if the feedback is caused by (1) above. If so, the fix is usually easy. Either move the person carrying the mic or move the speaker they are getting the feedback from. ’nuff said.
- Listen for the frequency. Is it in the range of vocals (from a low bass note to a alto ranged note)? If so, you need to adjust the mid-range level on the channel strip DOWN. Turn down the mid-range pot. If it is higher pitched than an Alto singer, turn down the Highs, if it is lower than a bass, turn down the Bass pot.
Now, I realize that the above solutions seem awfully easy, but really, if you use your ears, this is all you need to do. And, after all, that is what you are supposed to do.
Advanced Feedback Remedies
There are times when a particular frequency wants to feedback on several mics. This is due to the sound characteristics of the room. If you are having this issue on a regular basis, it is because you have not “dialed in” your room to allow for these characteristics. Every room will resonate certain frequencies differently than any other room. Therefore, you always need to adjust the equalizer for the room when you first set up your sound. Once this has been done (correctly), you really shouldn’t have to touch it. However, doing it properly requires an EQ (Equalizer).
Setting up the room EQ is done by turning up the sound pretty loud, and then turning up each frequency on the EQ (you usually want to have at least a 27 band EQ for this) until you hear feedback. Then back it off a bit so that you have a little bit of head room on each band.
Ideally, you would want one EQ for the mains and another for the monitors (assuming you have some monitors that are not “in-ear” monitors).
If you follow these advanced guidelines, you should be able to prevent feedback from occurring during the service … unless the guy who points his mic at the monitors shows up at your church!