Special Effects - Ashly DPX-100 Operating Manual

Operating Manual - DPX-100 Graphic Equalizer - Compressor/Limiter
If you are exceeding threshold frequently, your input signal is probably too high and
should be turned down. Of course, every situation is different, so experimentation before
final recording is always a good idea, but this is a good starting point.
To obtain a gentler limiting action at the expense of some dynamic range, decrease
the threshold to -15 and the ratio to 3-5. This is also a good starting point for analog
recording.
Broadcasting
Compression has long been used as a tool to make an audio signal appear louder. A
good example is in broadcasting, where competing stations with identical transmitters
and power attempt to sound louder than each other. Since they are all restricted with
respect to maximum audio level (modulation), their best tactic is to squeeze the dynamic
range of their programs to just a few dB. The audio output level of the station virtually
never changes, and the listener perceives this continuous high-level sound as being
louder than the same material in an uncompressed form. Although both compressed and
uncompressed programs reach the same peak levels, the compressed signal stays near
peak level more of the time, and thus sounds louder. This technique makes the broadcast
more intelligible over ambient noise, and increases the geographical area over which the
broadcast is audible to the listener. Additionally, this compression technique is extremely
useful for FM and infrared transmission systems for the hearing impaired.

8.3 Special Effects

Compression For Feedback Control
A common ritual in sound system set-up is equalizing the room to remove
feedback. This is generally accomplished by turning up system gain to purposely induce
feedback, searching for the center frequency of the feedback, and then equalizing at that
frequency to remove the feedback. Once this frequency has been cut, system gain is
again increased to induce another feedback point, and the whole procedure is repeated
until the engineer is satisfied that the significant problem frequencies have been
corrected. The major problem with this approach is that the feedback can easily get out
control, and the engineer ends up dashing back and forth between the mixer volume
controls and the equalizer controls, while every-one in the room plugs their ears and prays
it will end soon. The Ashly DPX-100 can turn this procedure into a fast, painless job,
eliminating loud feedback levels and the possibility of speaker or ear damage.
Procedure:
1. Set up the DPX-100 limiter controls as follows:
14