Compressor Threshold, Ratio And Gain; Attack, Release And Knee - Rane C4 Operator's Manual

COMPressor THRESHOLD, RATIO and GAIN

-10
-20 0
1.5
-30 +10
-40 +20
1
dBu
COMP THRESHOLD
The threshold, like crossing through a doorway, is the begin-
ning point of gain adjustment. When the input signal is below
the threshold, a compressor acts like a straight wire. Above
threhsold, the side-chain asserts itself and turns the volume
down.
In Compressor mode, COMP THRESHOLD defines the
absolute level, adjustable from –40 dBu to +20 dBu, above which
compression begins. If soft-knee settings are used, the threshold
is defined as the point at the center of the knee. (See the KNEE
description for more details).
In De-ess mode, this control defines the relative difference
between the broadband program material and the bandpass
signal defined by the PEQ. The ▼ pointer between –10 dBu and
–20 dBu shows the typical setting for De-essing.
RATIO defines the ratio of Input change to Output change,
and is adjustable from 1:1 (straight wire, no change) to 10:1
(heavy compression), as shown in Figure 9. For example, a Ratio
of 4:1 means that a 4 dB change at the input causes only a 1 dB
change at the output.
The ▼ pointer at 10:1 shows the typical setting for De-
essing.
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Figure 9. Input versus Output for various Ratio settings (hard knee)
Once you reduce the dynamic range using compression, you
can increase or decrease the overall loudness by adjusting the
GAIN. This control features a center-detent marking the unity
gain point, with a range of +12 dB or -12 dB on either side.
Manual-6
2 0
5 -6 +6
10 -12 +12
n:1 dB
RATIO GAIN
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ATTACK, RELEASE and KNEE

50
25
ATTACK
ATTACK determines how fast the gain is turned down once
the signal exceeds Threshold, and is adjustable from 25 ms (fast)
to 500 ms (slow). The ▼ pointer at 25 ms shows the typical set-
ting for De-essing.
RELEASE determines the rate of gain increase as less gain
reduction is required, and is adjustable from 25 ms (fast) to
2 seconds (slow). It is important to understand the difference
between release rate – as determined by this control – and release
time. The Release setting determines how long it takes for the
gain to change by 10 dB, not how long it takes to return to unity
gain (no gain reduction).
Example: with the Release control set to 1 s, when a signal
with 5 dB of gain reduction presently applied suddenly drops
below threshold, the release time is 0.5 s, calculated as follows:
Gain Reduction x Release = 5 dB x 1 s = 0.5 s
Auto Attack and Release
Unsure about how to set the Attack and Release controls?
Venue doors opening in 15 minutes and you need to speed
through sound check? No problem! Simply rotate the Release
control fully clockwise until Auto is lit, indicating the Attack
and Release settings are appropriately fixed for most types of
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program material. The C4's not entirely on auto pilot, though
– you still have full control over the Threshold, Ratio, Gain, and
Knee settings.
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KNEE controls the action of the compressor above and be-
low the threshold point. Hard knee does nothing until the signal
exceeds the threshold point, then applies full compression. Soft
knee begins applying a small amount of compression just before
the threshold point is reached, continues increasing compres-
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sion through the threshold point and beyond, finally applying
full compression to the highest level signals. Depending on the
application and source material, soft knee settings can sound
more natural. On the other hand for maximum loudness before
compression (for equipment protection for instance), use hard
knee settings.
Knee span is adjustable from 0 dB (Hard) to 10 dB (Soft),
with the Threshold always being at the center of this span. The
▼ pointer at the Hard Knee setting shows the typical setting for
De-essing.
100 500
125 1 s
250
50 2 s
500 25 Auto
ms ms
RELEASE
Auto
10 dB 10 dB
Hard Soft
KNEE