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In the treble band the same thing happens. If the release
time is very slow, the attack has no effect and the treble
(i.e. a Hi-Hat) lose impact. Faster release times increase
the presence of treble and overall "brightness," but can
produce a harsh sound for some musical styles.
Hold
When a signal exceeds the threshold, the compressor de-
creases its gain. The HOLD time maintains the degree of
compression regardless of the audio level. After the hold
time, the signal is released according to the recovery time;
or remains compressed if the level is above the threshold.
The longer the hold time the softer the compression, but
the loudness decreases.
4.6.2 MULTI-BAND LIMITER
The limiters work with an attenuation ratio of the order of
100: 1. Each band has 5 controls that adjust its action:
Figure 36: Multiband Limiter (MID2 band)
Threshold (THS) and DRIVE
Both controls affect the degree of limiting applied to the
band.
The DRIVE control applies gain to the signal before limit-
ing, that is, attenuates or amplifies the signal delivered by
the compressors. They are equivalent to the OUTPUT
LEVEL setting of the compressors. If Drive is increased
and the threshold is maintained, more peaks in the signal
will be limited, while increasing the energy in that band.
The THRESHOLD changes the level at which the limiter
begins to operate. Lowering the threshold increases the
limiting, but lowers the energy of the band, as the limiter
attenuates more peaks in the signal. To compensate for
the attenuation produced by the increase in the limita-
tion, the level of that band must be raised in the Density
Equalizer.
Attack and release
The limiters contain the impulse by keeping it at the
threshold level. During the attack time the limiter does
not actuate and lets the peaks of the signal pass to the
clippers, which will contain them with soft clipping.
Very fast attack times minimize clipping, but very fast at-
tack times can produce a sound that is too “flat”; without
dynamics and therefore unnatural.
Recovery time is the time it takes for the limiter to return
to a 1: 1 (linear) ratio after the signal falls below the
threshold.
4.7 Density EQ and Clippers
The "density equalizer" allows to re-configure the spec-
tral balance of the sound, determining in the final mix
the incidence of each band.
Figure 37: Density EQ
Note that the higher the level of a band in the Density
EQ, the closer it is to the threshold of the limiter, which
increases the loudness at the expense of reducing the
dynamics with soft clipping, which generates a more
"harsh" sound.
4.7.1 Band clippers
The band limiters are soft clippers that stop the peaks that
pass through the compression stage due to attack times.
Figure 38: Band limiters
The controls adjust the clipping threshold. The indication
"0" (zero) corresponds to 100% of the audio modulation. If
a threshold is set below zero, that band will never be able
to modulate 100% by itself; although the modulation can
reach 100% in the sum of the bands. If a threshold is set at
zero or above zero, it does not mean that the band will al-
ways reach 100% modulation, as that depends on the sig-
nal level present in that band, which is determined by the
"Density EQ".
The Level Indicators show the level present in each band
and the amount of limitation applied. The signal level in a
band can never exceed the threshold of the limiter. Above
the limiter threshold, the level indicator shows the amount
of clipped signal in orange.
Usually the band limiter is set to 100% or up to 1 dB below
zero, with the exception of the low band threshold usually
Page 36 Audio Processing Core - SOLIDYNE 542 APC