21
DUAL/STEREO COMPRESSOR/NOISE GATE CN-220
The compressor/limiter adjustment for this application depends on the speakers system
characteristics, but in circumstances in which the break risk of the speakers increases, many
technicians adjust the compression ratio to
∞
:1, that is to say adjusted like limiter, depending the
compression threshold adjustment on the speaker system characteristics.
PRODUCING THE TALKOVER EFFECT
To produce the talkover effect in the signal, all we have to do is to introduce part of the voice
signal (or channel line output) that we want to project from the general level, into the compressor
SIDE CHAIN input. When the signal introduced into the INSERT input surpass the compression
threshold, the program signal level will descend automatically. Of course, if we don't want the voice
affected by this compression, it should not be introduced into the compressor. This is easily achieved
using SUBGROUPS.
INCREASING THE OUTPUT LEVEL OF A MIXING SIGNAL
It is possible to separate voices and instruments of a mix signal, by means of a frequency
compression. The way to do it is to introduce a graphic equaliser in the compressor SIDE CHAIN
input. The equaliser must equalise the programmed signal, and must introduce it in the compressor
SIDE CHAIN input, while the compressor input is connected to the program signal (of course, this has
not been equalised). The bands amplified by the equaliser will show up more compressed in the
output signal, and the output signal will not be affected by the phase changes produced by the
equaliser, once the compressor threshold is reached. Of course, the output level of the whole
program is affected when the compression takes place, and so we will have to adjust the output
level control.
SOUND PRESSURE LEVEL CONTROL
The compressor/limiter has a wide range of application in sound pressure level control of
discos and pubs in order to warrant the maximum level authorised by the local authority. With this
purpose, it is always placed in the last point of the audio chain, that is to say, before the power
amplifier, or before the active divisor if working in multi-amplification. If the hall has a graphic
equaliser, it is highly advisable to keep it out of the reach of the DJ; that is why it will be protected
with a sealed lid once the equalisation has taken place.
To adjust the compressor, connect the compressor inputs to the equaliser outputs or mixing
console and connect the outputs to the power stage inputs. Choose a recording containing a big
percussive and loud sound. Adjust the pick-up sensitivity, that channel fader and the master to the
maximum. Select the STEREO operation mode by pressing the compressor STEREO button (the RATIO,
THRESHOLD and OUTPUT controls will depend on its adjustment in the CH1 channel in both channels
for this operation mode). Adjust the RATIO control to
∞
:1 if the hall is very problematic or to 8:1 if it is
not. Adjust the THRESHOLD (compression threshold) to the left until the GAIN REDUCTION indicator
indicates 15 dB in the program peaks. Adjust the OUTPUT control to -15 dB. Connect the power
amplifier/s with their gain controls to the maximum.
Now the moment has come to use a the sound pressure level measuring system, in the hall,
or in the street or behind the hall walls in the house subject to protection. Increase the OUTPUT
control by turning it to the right, until it reaches to the maximum level authorised for the sonometer in
that point. This operation is more reliable if the noises produced by the customers in the hall are
included in the measures.
If the outcomes are not entirely satisfactory, repeat every adjustment, but adjusting the
THRESHOLD until the gain reduction reaches 20 dB.
