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Old 30th March 2005, 04:22 AM   #1
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Default Convolving digital filters?

Hi,

I am running a digital xover and room equalisation system using BruteFIR. Currently I have 1k tap xover filters feeding 65k DRC generated filters for room equalisation. I was wondering how I might convolve these two filters - my knowledge of octave is VERY basic, I just followed someone else's instructions to generate the xover filters!

I also wondered what would happen if I was to convolve a 65k tap filter with another 65k tap filter - how many taps would the resultant filter have?

Many thanks,

Chris
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Old 30th March 2005, 05:55 AM   #2
wimms is offline wimms  Estonia
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http://www.dspguide.com/pdfbook.htm
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Old 1st April 2005, 01:36 AM   #3
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I have read the book up to the convolution part, and think I understand what it is saying, but still don't know the answer to my question. Can anyone answer my questions directly? I have tried to understand it but don't really have the maths background to manage it!

Thanks,

Chris
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Old 1st April 2005, 02:00 AM   #4
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Default Re: Convolving digital filters?

Quote:
Originally posted by birkinshawc
Hi,

I am running a digital xover and room equalisation system using BruteFIR. Currently I have 1k tap xover filters feeding 65k DRC generated filters for room equalisation. I was wondering how I might convolve these two filters - my knowledge of octave is VERY basic, I just followed someone else's instructions to generate the xover filters!

I also wondered what would happen if I was to convolve a 65k tap filter with another 65k tap filter - how many taps would the resultant filter have?

Many thanks,

Chris
I'll answer your second question first - you'll see why in a moment. Convolving an m-tap FIR with an n-tap FIR gets you a FIR of length n+m, so you gain nothing computationally by convolving FIRs. You might even lose some efficiency if BruteFIR uses a partition larger than your crossover filter length, because then you'd be calculating zeros stuffed into the coefficient set to fill out the partition.

In my opinion, you're better off keeping the crossover and DRC separate because you can tweak them individually.


Cheers,
Francois.
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Old 1st April 2005, 02:17 AM   #5
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Thanks for the info, just what I needed to know!

Chris
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