Specifications

Manual-3
Dynamic EQ
Dynamic EQ diers from the forms of compression listed above
in that it dynamically controls the boost/cut of a parametric
lter rather than broadband frequency gain. e basic dynamic
EQ uses a bandpass lter in the side-chain with variable center
frequency and bandwidth. e side-chain detector is sensitive
only to the passband frequencies. A parametric lter with match-
ing bandwidth and center frequency is placed in the main signal
path and the boost/cut of the lter is controlled the same way a
broadband compressor boosts or cuts broadband gain.
Relative Threshold Dynamic EQ
Relative reshold Dynamic EQ is a special form of dynamic
EQ where the rms level of the bandpass signal in the side-chain
is compared to the rms level of the broadband signal. e dier-
ence between the bandpass and broadband levels is compared to
the threshold rather than the absolute rms value of the bandpass
signal. e advantage of this type of dynamic EQ is that the
relative amplitude of a band of frequencies, as compared to the
broadband level, is maintained regardless of broadband ampli-
tude. e typical topology is shown in Figure 3.
INPUT OUTPUT
SIDE-CHAIN
ATTACK
GAIN COMPUTER
FILTER
THRESHOLD RELEASE
SCALE
RATIO
FREQ BW
BANDPASS BROADBAND
BANDPASS
RMS
DETECTOR
PARAMETRIC EQ
BROADBAND
RMS
DETECTOR
Figure 3. Relative threshold dynamic EQ block diagram.
De-essers
De-essing limits or controls the sibilant content of speech.
Sibilance produces a hissing sound. English sibilant speech
sounds are (s), (sh), (z), or (zh). De-essing is often confused as
a type of dynamics processor. It’s actually a specic application
that is accomplished using many dierent types of dynamics
processors. And contrary to popular belief, successful de-essing
is not as simple as placing a bandpass or treble-boost lter in the
side-chain and calling it done. Frequency Sensitive Compression,
Split-Band Compression, Dynamic EQ and Relative reshold
Dynamic EQ are all used for de-essing.
True de-essing involves comparing the relative dierence
between the troublesome sibilants and the overall broadband
signal, then setting a threshold based on this dierence, there-
fore it is our experience that Relative reshold Dynamic EQ
(as described above) is the best dynamics processor for this task
as it is able to maintain proper sibilant to non-sibilant balance
regardless of level.
A good de-esser looks at the average level of the broadband
signal (20 Hz to 20 kHz) and compares it to the average level of
a bandpass lter in the side-chain. e threshold setting denes
the relative threshold, or dierence, between broadband and
bandpass levels, which result in compression of sibilants. Because
de-essing depends on the ratio of sibilant to broadband signal
levels, it is not aected by the absolute signal level, allowing the
de-esser to maintain the correct ratio of broadband to sibilant
material regardless of signal level, as shown in Figure 4.
-45
0
-42.5
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-37.5
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-27.5
-25
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-20
-17.5
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-7.5
-5
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20 20k 50 100 200 500 1k 2k 5k 10k
Frequency (Hz)
Increasing Level De-essing
L
e
v
e
l
d
B
u
Figure 4. The C4’s De-essing performance remains consistent with
varying input levels.
is means that the de-essing performance is consistent and
predictable, regardless of how loud or quiet the singer/talker is.
Taming sibilance when the talker is quiet is just as important as
when the talker is at a fevered pitch.
Figure 5 shows what happens using a primitive de-esser
with a side-chain EQ. Sibilance during loud passages is attenu-
ated, but there is no gain reduction during quiet passages, even
though there may still be a signicant amount of “sss” in the per-
son’s voice. For a given threshold, this often results in an overly
aggressive eect during the loud choruses, and a completely
ineective result during the hissy, whispered verses.
20 20k50 100200 5001k2k5k 10k
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0
-42.5
-40
-37.5
-35
-32.5
-30
-27.5
-25
-22.5
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-17.5
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-12.5
-10
-7.5
-5
-2.5
Frequency (Hz)
L
e
v
e
l
d
B
u
Increasing Level
De-essing
No De-essing
Figure 5. Primitive de-esser with a simple side-chain.
Varying input levels adversely aects de-essing.