I want to use a 4th-order Linkwitz-Riley filter as a crossover in my system, but I don't see it available in the SigmaStudio library. How can I build this?
A 4th-order Linkwitz-Riley filter can be implemented by connecting two 2nd-order biquad filters in series. One series pair of these filters can be used for the high-pass, and a second series pair can be used for the low pass. When all of these filters are set to the same corner frequency, the corner of the resulting Linkwitz-Riley filters will both be at -6 dB. This results in a flat overall frequency response at the outputs.
This can also be implemented easily with SigmaStudio's crossover blocks, available in the Filters library. There are both 2-way and 3-way crossover blocks available. Clicking on the crossover block will bring up a design window where you can select the filter type and frequency, which is all displayed on a frequency response graph. By default, the filters are selected to be a 24 dB/octave (4th order, as described above) Linkwitz-Riley.See the image below for an example of a 2-way crossover set to 2 kHz corner frequency.
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