FIR filters: how to get the filter coefficients? - diyAudio
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Old 25th August 2005, 08:10 PM   #1
4real is offline 4real  Netherlands
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Default FIR filters: how to get the filter coefficients?

Hey there.

To make one thing clear: I don't want to talk about the pro's and con's of FIR filters! So don't start on that

So, what do I want to talk about then? Well, I'm interested in experimenting with an active 3-way speaker system. For this, I would like to use BruteFIR (like some others here on the).

But the thing is: you'll need to create the filter coefficients yourzelf. And sadly, I'm not an expert on that (I know the basics though). So I'm looking for some free software (preferably linux command line tools), to create nice phase-linear filters with as little pre-ringing as possible, with a fairly small tab size. Up until now, I didn't find anything usable. I looked at the sources of AlmusVCU (same author as BruteFIR), and found some stuff there to create some bastic filters, but I'd have to hack it a lot to create a usefull tool . So If you know some great tools, or some tutorial to use Matlab or Octave, please let me know! Also something to visualize the coefficients (frequency response) would be great.
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Old 25th August 2005, 09:28 PM   #2
4real is offline 4real  Netherlands
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Here a java applet that should do the trick:

http://www.dsptutor.freeuk.com/remez...terDesign.html

I only need to know if the coefficients are compatible with BruteFIR.
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Old 26th August 2005, 03:40 AM   #3
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Momentum Data Systems makes some nice design packages. You can get a demo version of QED 1000 to play around with, but it won't give coefficients unless you purchase it for $895 (dongle protected). There is a student version for $99 with fewer features. You will have to see if you can live with its limitations.

http://www.mds.com/Products/product....=QED%2DCOMPARE
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Old 26th August 2005, 03:53 AM   #4
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If you do this for a living, you could do far worse than ScopeFIR. It's a nice little Windows package with all the graphing you could possibly want, including graphs of imported coefficients, which comes in quite useful when using subtractive FIRs for the other band ((delayed signal) - FIR LP = FIR HP).

http://www.iowegian.com

It's a hundred bucks; I've gotten many times that much use from it.

Frankie-Bob says two thumbs up!


Francois.

disclaimer: no ties to iowegian whatsoever, just a satisfied customer.
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Old 26th August 2005, 09:30 AM   #5
4real is offline 4real  Netherlands
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All very nice, but there are two problems: those are Windows tools, and those are NOT free


3'rd problem is that I want to integrate in into a home-made crosover designer that will spit out a BruteFIR config file automagicly.
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Old 26th August 2005, 11:11 AM   #6
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http://www.geocities.com/weiruan97/dfd/dfilter.html

And i got a few more of which i do not have the links available currently.

grtz

Simon
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Old 26th August 2005, 11:20 AM   #7
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Quote:
And i got a few more of which i do not have the links available currently.
I do

http://www.nauticom.net/www/jdtaft/

grtz

ST
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Old 26th August 2005, 11:35 AM   #8
4real is offline 4real  Netherlands
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Thanks those look great.

But I still think my first java applet is the most usable, since I also have sources of that one.
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Old 26th August 2005, 02:37 PM   #9
RR is offline RR  Europe
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Hi:

Try this Octave script:

http://www.duffroomcorrection.com/wiki/User:Birkinshawc
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Old 26th August 2005, 02:40 PM   #10
4real is offline 4real  Netherlands
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Thanks! That is really nice! I'll look into that as soon as possible!
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