Flexibility really matters when it comes to innovative speaker design. As DIYers and speaker designers ourselves, we came to realize that miniDSP platforms could be used for both basic and advanced digital signal processing applications. While textbook filter implementation like Butterworth, Linkwitz Riley, and Bessel work in 80% of configurations, some speaker designers may want to investigate novel IIR filter implementation like:
- Filters currently not implemented inthe basic mode
- Cascaded filters
- Custom filters developed on 3rd party software
The following section will teach you how to use our advance programming.
DISCLAIMER: The following section assumes that you have some basic understanding of filtering and Digital Signal Processing. Testing the accuracy of a filter before loading it to the miniDSP must be performed ahead. Once loaded inside the miniDSP, you should first confirm the overall transfer function to confirm that your biquad computations are correct. miniDSP cannot be liable of incorrect/unstable plug-in biquad settings being loaded into the platform.
miniDSP filtering is based on 2nd order linear recursive filtering, also called a Biquad digital filter. A biquad contains two poles and two zeroes with a transfer function expressed as follow in the Z domain.
All filters of miniDSP (PEQ/Shelf/Graphic EQ/Low Pass/High Pass) are all implemented using the 5 coefficients of the a 2nd order filter. (a1/a2/b0/b1/b2). Note that a1 and a2 need to have sign inverted (times -1) due to the DSP implementation.
Biquad programming on miniDSP plug-ins is allowed on all biquad objects of the DSP structures. There are currently 2 places were custom biquad can be implemented:
Adding them up together, a total of 68 biquads will give you all the flexibility you need to create your custom processing.
Advanced Biquad programming trully opens the door to a new range of filtering applications such as: