FIR filters

jami schorling

New member
Aug 21, 2019
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germany
Hi Mark,

With the latest updates in Version 1.5, I've come up with some example screenshots which might help.

Lets say after filtering, you want the mid driver to have a response of LR24 HPF minimum phase at 100 Hz and LR24 LPF linear phase at 650 Hz.

In FIR Designer,
- choose the "Direct Design" mode
- set two of the filters on the Magnitude Design tab (one to Min LRHPF 4th order & another to Lin LRLPF 4th order)
- set the filter delay and length fairly large so there is negligible error from windowing (e.g. 2048 and 4096 samples)
- export (e.g. to 24 bit wav file.)

View attachment 202086 View attachment 202079 View attachment 202078

This file will be the "Target"

In FIR Designer
- In the menu, select Project -> New
- Go to the Target tab, select File and Load the above WAV file. Set the delay to minus the filter delay from Direct Design above. (e.g. -2048 samples)
- Go to the Import tab, load your measurement, then take a look at the way I've configured the settings on the all the tabs.
- The result is you have a FIR filter that will filter the driver to meet your target magnitude and phase response, including crossovers, down to -12 dB on the sides or a little lower.

View attachment 202083 View attachment 202077 View attachment 202082 View attachment 202084 View attachment 202081 View attachment 202080 View attachment 202085

I'll email you the files too.

Best,
Michael

Since I didn't know about APL C5, I followed your approach but for APL Workshop - Defining per Driver Target Curves, then measure the drivers seperately (either with or without IIR-crossovers) and then combine them and correct possible phase issues in the crossover region with delay/allpass filters. Results are good so far, although I haven't been able to recreate a TDA graph that comes close to Peter Morris results.
 

ghaze stor

New member
Nov 20, 2022
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I would check out some of the papers Bennett posted in post 17. Dave details quite well his different applications and processes. Just a note that much of what he is doing may be protected under patents, so I wouldn't except other companies to be able to implement his technology without specific agreements.