mi niDSP Ltd, Hong Kong /
/ Features and speci fi cations subject to change wi thout pri or noti ce
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5.4
C
USTOM BIQUAD PROGRAMMING
Custom biquad programming is available in the parametric EQ and crossover blocks. Its purpose is to allow you
to directly provide the low-level parameters aka biquad coefficients that control the digital filters, thus providing
an almost infinite degree of flexibility.
For example, you can create hybrid crossovers with more than one cutoff frequency, create crossover filter
types beyond those provided in the easy-to-use “basic” interface, implement a Linkwitz transform, or mix
crossover and filtering biquads in the same block.
5.4.1
What’s a “biquad?
A biquad is the basic unit of processing that is used to create digital filters. It can be described either with an
equation or with a signal flow diagram, as shown here:
A single biquad like this can perform a great many functions, including all of the functions of a single parametric
EQ filter, one 6 or 12 dB/octave high pass or low pass filter, and more. Biquads are combined in series
(cascaded) to create more complex filters. The function that each biquad performs is determined by just five
numbers: a1, a2, a0, b1, and b2. These numbers are called the coefficients.
5.4.2
Using custom biquad programming
Each crossover block and parametric EQ filter has a selector that switches it to advanced mode:
In advanced mode, the biquad coefficients are pasted directly into the user interface. These coefficients must be
calculated using a filter design program – see the following sections for suggestions.
Note that when using a filter design program, the sample rate must be specified at the correct rate for the
plugin – 48 kHz for the PWR-ICE2-2x2-FIR plugin, and 96 kHz for the PWR-ICE2-2x2 plugin.
