12 Public address
Part 2
Howl-rounds
Figure 12.1 shows in diagrammatic form the fundamentals of a PA situation. The amplifier feeding the loudspeakers raises the signal level, while there are losses in the microphone, the loudspeaker and the room itself.
If the gain (amplification) is greater than the total losses then there will be a howl-round. However, if the amplifier is set so that this is not in general the case there can still be trouble if, at any frequency, there is an extra gain caused by the addition of the frequency responses of the main components.
Figure 12.2 illustrates what might be typical frequency responses of the main components in a PA ‘loop’ – the chain which is capable of causing a howl-round. Those components are:
1. The ...
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