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DSP MODULE - PEQ - PARAMETRIC EQ
An adjustable filter used to shape the frequency content of a signal. The parametric equaliser allows control
of several frequency bands. Although more complex than other types of equalisers, a Parametric EQ provides
surgical precision and fine tuning.
Its parameters are:
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TYPE: the PARAMETRIC equaliser is the default. To apply a different type of filter, you must enable the
filter (ON) and select from the drop-down menu among the different filters available: PARAMETRIC,
LOWSHELF, HIGHSHELF, LOW PASS and HIGH PASS.
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HIGH/LOW PASS: are pass filters in which the filter frequency is called the cut-off frequency. A pass
filter allows frequencies on one side of the cut-off frequency to pass completely through the filter,
while frequencies on the other side of the cut-off frequency are attenuated. A HIGH filter allows
frequencies above the cut-off frequency to pass through and filters frequencies below the cut-off
frequency, while a LOW filter allows frequencies below the cut-off frequency to pass through and
filters frequencies above the cut-off frequency.
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HIGH/LOW SHELF: HIGH filter of this type causes the gain to boost or attenuate frequencies above
the set frequency. While a LOW-cut filter causes the gain to boost or attenuate frequencies below
the set frequency. The set frequency is not the 3dB cut-off frequency, but refers to the centre of the
falling edge or the rising edge of the filter. The Q factor affects the peak and has a mathematical
relationship to the peak.
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FREQ (Hz): centre frequency.
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GAIN (dB): gain boost or attenuation at the set centre frequency
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Q: filter quality factor. The higher the value, the lower the frequency range it affects. That is, the bandwidth
around that frequency that is affected.
When the filter is a PARAMETRIC filter, the Q value refers to the width of the bell-shaped frequency
response curve on either side of the centre frequency. When the filter is a HIGH/LOW SHELF or
HIGH/LOW PASS filter, if Q>0.707, there will be peaks in the filter responses If Q<0.707, the slope will
be flatter and the roll-off will occur earlier.
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OCT: changes the Q-value units to octaves. When it comes to musical content, measuring bandwidth
in terms of octaves can provide more musical results. A wider octave setting will make the content
more natural and musical, at narrow settings it lets you know which musical notes you are affecting as
determined by the centre frequency.
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ON/OFF: enables or disables the filters. The first control on the left enables/disables all filters globally
and the rest act on each filter individually. If OFF (disabled) the signal is not processed by the filter.
NOTE: the ON/OFF control that applies to all filters must be ON for the module to have any effect on the
signal. When ON the lower part of the graph curve will be coloured blue.
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