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Feedback Prevention
When the overall gain of a sound system is increased,
feedback will occur at frequencies where the system response
has peaks. Suppose the system has an uneven frequency
response like that shown in the following diagram. The
frequency at which feedback will occur when gain is
increased is about 500Hz. In this case, feedback may be
prevented by attenuating levels at 500Hz by 3dB to 5dB with
the E131. If the overall gain is again gradually increased,
feedback will occur next at about 125Hz. It may be stopped by
attenuating the levels 2dB to 3dB at that frequency. In this
procedure, sufficient gain in the sound system is obtained
before feedback.
Room Equalization
In a sound reinforcement system for a room, the clarity of
sound can be adversely affected by the room frequency
response including standing waves (room resonances),
reflections of sound, and relations between direct and
indirect sound.
The E 131 is an effective tool to equalize the room frequency
response to a flat response and improve sound clarity.
For example, suppose that there is a room frequency response
as shown below.
Sound
Pressure
Level
Frequency
The equalizer sliders are set as shown below.
The overall response after equalization will then be as
follows.
Before equalization
Frequency response
of equalizer
Frequency response
after equalization
Sound
Pressure
Level
Frequency
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