Page 18
C2
Operators Manual
Sidechain Equalisation – How and When to Use it
When would Sidechain EQ be useful?
When it is necessary to adjust the sensitivity of the compressor, tailoring the sidechain
signal with equalisation is the only way to achieve this without affecting the main signal
path.
De-essing and de-popping.
For example, a de-esser is really a compressor that has had its sidechain made more
sensitive to sibilance (sounds such as ‘s’ and ‘t’), which occurs in the range 6kHz to
9kHz. A de-popper will be a compressor sensitised to respond to low frequency
plosives (sounds such as ‘p’ and ‘b’) in the range 80Hz to 150Hz.
In reality, the attack and release times of the compressors as implemented for
de-essing and de-popping will be set appropriately to prevent the compression having
too great an effect on the overall signal.
Both of these examples illustrate using the sidechain EQ to make the sidechain more
sensitive to certain ranges of frequencies. It can be very useful to be able to de-
sensitise the sidechain to certain frequency bands to prevent excessive activity at
inappropriate times.
Maximising loudness without dulling the mix.
Loudness, as opposed to volume, is dependant on the signal density as much as the
level and so compressing the program can increase the perceived loudness without
actually requiring more headroom. For example, consider the situation where bass-
heavy program material is to be compressed to maximise loudness in a live situation.
The spectrum might look like this.
If the threshold was set
to 0dB (the dotted line)
it can be seen that the
compressor will start to
act first when the low
frequency part of the
spectrum crosses the
threshold.
This will have the effect of pulling down the level across the
entire
spectrum
(including the high frequencies) and so causing the familiar ‘dulling’ that can easily
occur with full range compression. The solution to this problem is to introduce some
complementary sidechain EQ that will remove some of the offending bass from the
control signal, making the compression more ‘even-handed’ again. The required
effect on the spectrum would be similar to that shown below.
Summary of Contents for C2
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