Killing sound system feedback

The biggest problem in PA system that most technician hate most is the mic feedback. Feedback is not that hard to eliminate as long as you know what is the cause. There are several common sources of feedback that I will share to you and simple solutions to kill feedback on your system.

What is feedback?

Feedback happens when the output is being fed to the input again, in this case the input device is the microphone and the output device is the speaker. Feedback happens when the microphone hears the speaker connected to it, creating a loop and will never stop until you interrupt it. Feedback has different pitch or frequencies. The pitch(frequency) of the feedback determines the dominant frequency. Some technician always lower the treble volume to eliminate feedback which is not correct. If your feedback pitch is low, this indicates that you may have very dominant bass frequency on your system. You can eliminate the feedback by decreasing the frequency of the feedback using graphic or parametric equalizer.

Common Sources of feedback and solutions

1. Un-equalized system
   Equalizers are usually used to “equalize” the systems frequency response. This is done by cutting dominant frequencies and boosting weak frequencies. Some people set the equalizers in a “V” shape pattern and make the system more “un-equalized” rather than equalized.
   
   While this setting is acceptable to home sound systems, it is a different story in PA systems. Setting this in a PA system will make you prone to low and high pitch mic feedback.
2. Speaker placement
   The speakers and mics should have enough distance with each other. Main speakers should be placed where it is not facing the microphones. Monitor speakers are basically facing the mics so they should have separate volume controls. Watch out for the volume setting of the monitor speakers. It should only be loud enough for the singer to hear in a close range.
3. Under power system
   If you have under power system, chances are you will crank the gain of the mic up. There is always a maximum gain for every setup and you might reach that maximum gain when your system has insufficient power.
4. Room Acoustics
   Every material has resonant frequency, this frequency is the natural oscillating frequency when it vibrates. When the sound produced is equal to the rooms material resonant frequency, it tends to amplify that sound and might create some feedback on your system.
5. Wrong Mic handling
   Common problems on singers that they sometimes hold the mic on a wrong way. The windscreen of the mic should not the covered with your hands. This makes the mic more sensitive to one direction and is it is like increasing the gain or volume of the mic which will led to feedback.