3.4 FFeedback
Fig. 2: Microphone
placement for maximum
gain before feedback.
Refer to fig. 2.
The term “feedback” means that part of the sound projected by
a speaker is picked up by a microphone, fed back to the ampli-
fier, and projected again by the speaker. Above a specific vol-
ume or "system gain" setting the sound system will start howl-
ing and the sound engineer will 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. It is most sensitive to sounds arriving
from in front of it (your voice) while picking up much less of
sounds arriving from the sides or rear (from monitor speakers
for instance).
To maximize gain before feedback, place the main ("FOH")
speakers in front of the microphones (along the front edge of
the stage).
If you use monitor speakers, be sure never to point any micro-
phone directly at a monitor or FOH speaker.
Feedback may also be triggered by resonances depending on
the acoustics of the room or hall. With resonances at low fre-
quencies, proximity effect may cause feedback. In this case, it is
often enough to move away from the microphone a little to stop
the feedback.
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