AKG C451, User Instructions, Page: 19 / 76

C451 65th Anniversary Edition 19
Application
Feedback results from part of the sound projected by a speaker being
picked up by a microphone, fed to the amplifier, and projected again
by the speaker. Above a specific volume or “system gain” setting
called the feedback threshold, the signal starts being regenerated
indefinitely, making the sound system howl and the sound engineer
desperately dive for the master fader to reduce the volume and stop
the howling.
To increase usable gain before feedback, the microphone has a
cardioid polar pattern. This means that the microphone is most
sensitive to sounds arriving from in front of it (from the sound source)
while picking up much less of sounds arriving from the sides or rear
(from monitor speakers for instance).
To obtain maximum gain before feedback, place the main (“FOH”)
speakers in front of the micro phones (along the front edge of the
stage). If you use monitor speakers, be sure never to point any
microphone directly at the monitors, or at the FOH speakers.
Feedback may also be triggered by resonances depending on the
acoustics of the room or hall. With resonances at low frequencies,
proximity effect may cause feedback. In this case, it is often enough to
move away from the microphone a little to stop the feedback.
Feedback in Live Sound
Situations