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TOPIC: Re: Linear phase IIR filters?

Re: Linear phase IIR filters? 8 years 6 months ago #4466

  • curryman
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Wow, great looking speaker! :)

Audiovolver from Audiodata is quite similar to your proposed setup (PC with accourate/bruteFIR), though I am not sure if it is multichannel. Quite pricey...

looking forward to follow your further developments ;)
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Re: Linear phase IIR filters? 8 years 6 months ago #4468

  • Jakster
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I just read through this thread again and I guess I wrote a little fast and didn´t read your entire posts - sorry about that.

WMTMW it is :-) and apparently it is possible to do this using IIR BIQUADS (however finding the allpass IIR filter (reverse phase filter) for each of your biquads and speaker response might not be trivial). I would still leave the whole IIR filter world and enter the FIR world, and thereby discard using the miniDSP.

I haven´t really started using Scilab yet - I used to work in matlab but since I can´t afford the licence I am going to start using scilab. Scilab should be able to create the filters you need, but if you´re not accostumed to matlab and digital signal processing in general, there is a steep learning curve (windowing, fft, ifft etc). I don´t know your theoretical background so if this in any way sounds patronizing, its not my intension - I just want to make sure that you understand that you need to design the filters from scratch - not via "point and drag" interfaces such as acourate. You also need another program to do the measuring of acoustic responses (fx holmimpulse or REW).


As you say you need your filter (IIR or FIR) combined with the acoustic response of your speaker unit to give the desired linear phase crossover response at depicted in your post. I´ve done this previosly and if I remember correctly we used a wiener filter (en.wikipedia.org/wiki/Wiener_filter) - though we used a different target response.

I have not created "arbitrary linear phase responses" (target functions), so I can´t give you much advice in this direction, other than it´s probably done in frequency domain and inverse fftéd.

regarding brutefir - I think Acourate has a brutefir usb linux version for free download (but it´s probably the same one as you saw). What kind of soundcard will you be using??

Amazing looking speakers by the way - a lot prettier than what I´ve got.
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Re: Linear phase IIR filters? 8 years 6 months ago #4473

  • Crumboo
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Hi, since this is getting off-topic I created another thread. :)
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Re: Linear phase IIR filters? 8 years 6 months ago #4722

  • Katz
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Might a future multichannel OpenDRC be 4x8, and can provide linear phase XO and EQ for three (L/C/R) 2-way speakers, and EQ for two subwoofers?

Could this be done now with two of the existing OpenDRC?

Sorry if that's a dumb question, but there's only a data sheet for the digital version, and I can't tell from that how many output channels there are.
__________________________________________
Noah
Last Edit: 8 years 6 months ago by Katz.
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Re: Linear phase IIR filters? 1 year 1 month ago #42984

  • eclipseaudio
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It's been a very long time but I just found this thread whilst searching for something else.

@Crumboo
Adding the @Jakster's comments, reverse IIR's can be emulated by creating a "maximum-phase" version of any common IIR filter, sampling the impulse response, and implementing this in a FIR filter block.

Our FIR Designer and FIR Creator products can do this. On the Mag Adjust tab, select a common IIR filter then set the phase to "Max." On the Export tab, set the Filter Delay equal to the Filter Length. Done!

BTW FIR Designer and FIR Creator also have the Keel/Horbach filters.

Kind regards,
Michael
Eclipse Audio
Maker of FIR Designer and FIR Creator - filter design tools for loudspeakers.
www.eclipseaudio.com
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