by Pat Brown
Pat Brown points you to some additional resources on FIR Filters.
It’s been just over one year since I posted FIR-ward Thinking – Parts 1 and 2. How time flies. Robert Bernecker followed with his excellent A Simple Exercise in “Practitioner Level” FIR Filters in March of this year. If you have digested these and want to go farther, I have some resources that I can point you to.
1. Filter Hose
Filter Hose is a Windows software that generates FIR filters from imported measurements. Rather than try to list all of the details here, I will just point you to the website (http://www.hxaudiolab.com/filter-hose.html). There are some excellent video tutorials on the site. Take a few minutes to learn about the developers, Hadi Sumoro and Xian Yu. Their experience in professional loudspeaker design makes Filter Hose especially interesting.
Still in beta, FIRCapture is a special version of WaveCapture that includes a FIR generation engine. Since it is both a measurement platform and FIR generator, it is especially powerful for driver compensation in systems. It can produce both IIR and FIR filters, and includes a optimization engine that produces a set of parametric filters that will equalize a measured response in combination with FIR filtering. Thanks to this mixed phase technology powerful equalization in both frequency and time domain are achieved with a minimum of latency.
I will be using Filter Hose and FIRCapture in our OptEQ workshop on January 5-6, 2015 in Dallas. I’ll generate some FIRs on the fly and we’ll all have a listen and discuss the trade-offs between flat magnitude, linear phase, latency, etc. Deward Timothy and John Murray will be using SysTune and Smaart, respectively, so attendees will get a good look (and listen) at how these tools can be used to optimize a sound system. Our demo systems include a point source, point source array, passive straight line array, beam-steered line array, and a discrete box curved line array.
We are now seeing FIR filter implementation on a number of DSP platforms, so the interest in these powerful filters is growing fast. pb