Sonnox Oxford SuprEsser - Manual (Page 18)

3.3 AdvancedOperation 3 OPERATION
3.3.3 BandpassFilterModes
BandpassMode
By default, the Oxford SuprEsser uses a bandpass filter (along with its inverse filter,
the band-reject filter) to isolate the audio in the frequency range selected. The
FREQUENCY and WIDTH controls defines the low and high edges of the filters used,
and the SLOPE/Q control defines how quickly a signal blends from gain-ducked to
non-gain-ducked in the frequency spectrum. The effect of less steep slopes is to
give a smoother blend between gain- reduced and non-gain-reduced regions of the
frequency spectrum, at the cost of a less specific trigger.
In this mode, the bandpass filter is created by using pairs of Oxford R3 Filters, giving
a total of up to 72 dB per octave of separation.
There are three other modes possible, which automatically switch into operation in
certain situations:
High-Q NotchMode
When you reduce the WIDTH control all the way down to 0.2 octaves, you activate
High-Q Notch mode. In this mode, instead of using R3 Filters, the plug-in uses four
Oxford EQ Type-2 Filters, giving a total of 80dB of gain reduction at the centre point
of the notch. This mode is useful when the band of energy you are interested in
reducing is extremely narrow, or virtually a single frequency, like a whistle.
In this mode, if desired, you can reduce the Q of the filters by reducing the SLOPE
control. The effect of this is to give a smoother blend between gain-reduced and
non-gain-reduced regions of the frequency spectrum, at the cost of a less specific
trigger.
LF-CutFilterMode
When you reduce the left edge of the bandpass filter all the way down to 20Hz, you
activate LF-Cut Filter mode. This means that the lower edge of the bandpass
window is effectively at 0Hz, and this is useful, for example, when working on
eliminating sub-bass plosives and thuds/booms that contain DC components.
In this mode you can think of operation as an LF-Cut Filter that activates only when
the signal reaches a certain threshold, in which the cut-off frequency is defined by
the upper edge of the bandpass window.
HF-CutFilterMode
When you increase the right edge of the bandpass filter all the way up to 20 kHz,
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