Symetrix 528 - De-esser Functionality

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sidechain is routed through a pair of rear panel barrier strip terminations that allow the
control signal to be processed outside the unit (see Section 2.4 for specific hookup
information).
Look at the block diaiiram in section 2.3. Notice the SIDECHAIN terminations that come
fro m the comp/limit/expand section. They allow access to the control circuit that is
taken fro m the audio si1P1al at the dynamic range processor's input. This control si1P1al
is derived from, but kept totally separate from , the audio si1P1al path. That means the
contro l si1P1al can be processed outside the 528 without actually processing the signal
that's going thro u gh the VCA (the audio sigoal itself). This presents some very
interesting possibilities for changing or improving the operation of the dynamic range
processor.
The best use of the sidechain is to make the action of the 528's co m p/limiter/expander
frequency dependent, that is, to make it respond more (or less) to certain frequencies.
Beca u se the audio si1P1al and the control si1P1al remain completely separate (even while
the control circuit tells the VCA whether to tum the gain up or down), you can equalize
the sidechain without chanaing the EQ in the main audio path.
Removing unwanted frequencies from the control si1P1al before it actually reaches the VCA
prevents those frequencies from beina used to create gain changes. And perhaps most
importantly, this is accomplished without actually equalizing the signal being processed
through the 528. Applications utilizing the sidechain may be found in Section 4.
1.1 5 De-es ser
A de-easer is another type of dynamic range controller that's specially desigoed to
re2t1late hitih frequency content. The technique was originally developed for motion
pictu re dialogue recording, when it was discovered that speech sounded more natural and
pleasing when the accentuation of sibilants was reduced. By sensing and limiting
certain selected frequencies, the de-esser is intended to provide more specific control
over some of the higher frequency vocal sounds that tend to become over emphasized.
Many sibilant vocal sounds like "s," "sh," and "t" are very difficult to reproduce
electronically, because they contain a large percentage of very high frequency harmonics .
But because these sounds are so essential to the intelligibility of speech , they cannot
be simply removed with equalization. In fact, to help maintain articulation many sound
enaineers boost the higher frequencies of the vocal spectrum (3kHz to 8kHz), and / or use
microphones with "presence curves." However, in certain individuals sibilant sounds are
already over accentuated, and any kind of high frequency boost only exacerbates the
situation.
The 528's de-esse r controls excessive sibilant and fricative vocal sounds , which can
often be as much as 12dB louder than the rest of the spectrum. It's activity is similar
to a frequency conscious co m p/limiter (with an equalizer boosting the high frequencies in
its sidechain). Unlike a comp/limiter however, it operates only on the frequencies
selected. And unlike an equalizer the de-easer can reduce the offending sounds without
sacrificing intelligibility. because it operates dynamically. It removes only sounds that
are disproportionately loud, and only those that fall within the operator-selected control
range .
De-essers usually include controls that allow the ope r ator to determine which freqeunci e s
are controlled, and how much those frequencies are actually attenuated. The 528's de-
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