by Dale Cohen
How often have you seen the MC at a wedding walk too close to the speaker, and the whole pa speaker system shutters with a feedback loop.
This is a common occurrence, however it can be avoided and is worth implementing steps to mitigate the risks of it arising.
Feedback occurs when the amplified sound of a loudspeaker re-enters the system through any microphone and it is amplified again and again, creating a loop. Feedback can occur in even the smallest PA Systems and can only be stopped by closing the loop.
There are numerous methods to stop feedback and reduce the severity. We have listed below some techniques to do so.
When the person speaking is directly in front of the speaker, it makes it easy for the system to feedback. To avoid this, try placing the speaker away from the person speaking. An example of this on a stage would be placing the speakers at the front of the stage facing outwards, with the person speaking on stage and behind the speakers. If needed a foldback speaker can then be provided for the person to hear themselves clearly.
Using a graphic equalizer
A graphic equalizer has the ability to lower specific audio frequencies which are feeding back through the system. An example of this is the DBX 231 Graphic Equalizer. This unit provides two 31-band channels of 1/3-octave equalization and can assist in reducing the likelihood of feedback when used correctly.
Monitoring line levels
Feedback is most common when the audio levels passing through the PA System are too high. With proper mixing we can lower the gain on the microphone being used which reduces the spill area of the microphone’s diagram.
DSP (Digital Signal Processing) is the use of specialized computers to perform a wide variety of signal processing operations. Once the DSP takes the live audio signals, it digitizes the sound and processes it.
The machine can then reduce feedback in a system through its programming. This is most commonly found in videoconferencing systems such as Zoom, but can also typically be found in high-end audio PA Systems.
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