Correcting group delay

[SoundRight]

I have read somewhere it is possible to correct for gd in bass reflex and presumably band pass subwoofers with dsp processing without effecting the original frequency response? Anybody have any observations on this....or does it require specifically programming ffr filters?

I am guessing it is not simple or others would be doing it. I have the simulated gd curve I am trying to correct and my guess is it can never be perfectly zeroed but at these ftequencies reducing it to single figures would be sufficient to "hear" the improvement?

 

[lcsaszar]

Just speculating. There is no negative delay, so you can't remove what is already there. Only option would be to variable add and make GD flat and constant over the useful range. But then the woofer will have higher GD at the XO than the mid/tweeter.

 

[SoundRight]

Hi,

Thank you. I understand you can't have negative delay. I read an article where using ffr filters in DSP it is possible to correct the GD curve of the subwoofer and I am wondering how this is achieved. If it is in DSP which I use in all my systems it is easy to delay the signals to the main speakers of course but this would only be relevant to matching the gd's of sub to mains?

 

[SoundRight]

Here's the article!

"Proc. of the 17th Int. Conference on Digital Audio Effects (DAFx-14), Erlangen, Germany, September 1-5, 2014" Article by Stephan Hertzog "Low frequency group delay equalization of vented boxes"

Problem is I didn't understand much of it..but it seems that a "time filter" response can be inverted to cancel the GD of the system.

Anybody able to put all this in to laymans terms..like having got the simulated response, impedance and GD curves how you go about creating a filter in DSP to achieve the results of "equalised" GD!!

 

[weltersys]

If it is in DSP which I use in all my systems it is easy to delay the signals to the main speakers of course but this would only be relevant to matching the gd's of sub to mains?

Yes.
You might check out this thread:
http://www.diyaudio.com/forums/mult...hase-linearization-eq-fir-filtering-tool.html

Around post #43 there are some discussions regarding EQ.

 

[SoundRight]

Thanks....will take a look.

 

[Viennatom_new]

there is no negative delay but delay can be compensated by adding matching delays for the other frequencies that are not affected.

 

[SoundRight]

Thanks Vienna...take a look at the article link...of course you can't have negative time!

 

[xrk971]

You might find useful info here:
http://www.diyaudio.com/forums/full-range/273971-group-delay-questions-analysis.html