I will be adding different ways to troubleshoot a sound system as time goes by. There is some material available now for your review, but check back in future to see the new items I’ve added.

Eliminating Feedback with EQ

You can eliminate much feedback with the EQ by “ringing out” the room. This is a simple process, if tedious, but I guarantee that you will like the results afterward. This is best done with a graphic EQ rather than using the EQ knobs on individual channels for many reasons, if not only to preserve the use of those precious knobs for sound shaping instead of dedicated feedback eliminators. If you find that vocals feed back a lot no matter where they stand, there’s a good chance that one or more frequencies are bouncing around the room and finding their way from the mains back into the microphones (thus the term feed + back). These buggers can be rooted out with only a few people and a good graphic EQ for the global mix (attached to the mains instead of to a specific channel).

Step 1: Insert the graphic EQ into your signal chain going to the mains.

Step 2: have someone take a microphone on the stage where the singers normally stand.

Step 3: Assuming your Mid has a Q knob, take that all the way up to narrow the frequency range to the minimum.

Step 4: Boost the gain to the Mids. Not all the way so it feeds back, but right at the brink of feedback.

Step 5: “Sweep” the Mid Frequency knob until you find the ringing to be instantaneous when you bring up the faders, note the frequency.

Step 6: Pull it back with the graphic EQ so it is reduced until you have fewer troubles with that feedback frequency.

Step 7: Repeat steps 1-6 (multiple times in each spot the singers stand) until all major feedback frequencies are eliminated.

This process is not meant to keep feedback from ever happening in your room again, nor is it intended to remove all frequencies that can cause feedback in your system (that would absolutely ruin your mix!). This process is meant to reduce the frequencies that cause the most trouble in your room by finding the frequencies that bounce around and tend to get back into the microphones and cause the easy, common feedback.