Feedback in Indoor Venues

While we usually associate feedback problems with monitors, reflected sound from the mains can also be a problem. This is more likely in indoor venues, but can be a problem anywhere that has surfaces that can reflect main PA sound back to the stage.

Nearly any surface can become a mirror reflecting sound back to the stage. High frequencies are more prone to this sort of a problem, and they are the ones that are most likely to produce a feedback loop. Flat surfaces common in clubs and indoor venues are the most likely to cause problems, but even rounded objects can cause problems.

Feedback is a sound loop at a specific frequency. The higher the volume the more likelihood of encountering feedback problems. When the microphone ‘hears’ the looped sound louder than the main sound you will probably get feedback.

The solution to feedback is to take the problem frequencies out of the equation with an EQ notch at the frequency causing the problem. Typically a one-third octave EQ is used for this. The problem is to remove the feedback frequency without destroying the sound quality. Apply the minimum amount of EQ to eliminate the problem will help to maintain sound quality.

If the source of the problem can be identified a sound treatment may be in order to alleviate the problem. In some cases a thick pile carpet may help or acoustic foam may be applied. Identifying the source may be difficult as these problems can be transient in nature depending on where things and even crowd is in the room.

Feedback problems can be difficult to deal with but must be dealt with to give a good quality to the show. If you have persistent feedback problems you will need to chase them until you find the best solution for the sound quality and the quality of the performance.

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One Response to “Feedback in Indoor Venues”

  1. Daniel Says:

    Having the room full of people can also help alot! If the high frequencies are the problem then people themselves block and disperse these frequencies and stop them slapping back to the mic. I hate sound checking a band and getting it in the ear because of feedback on the mics. I assure them that once the room fills up it wont be a problem!