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Multi-Way Conventional loudspeakers with crossovers

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Old 5th January 2013, 02:15 PM   #251
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Quote:
Originally Posted by more10 View Post
Personally I will not enjoy listening to a system not knowing exactly what it is doing.
I am totally with you on this, and would not stand any risk for my precious compression drivers... (2450SL+Truextent diaphragms and ET703 tweeters)
I think it is okay to buy several miniSHARC cards ($175 apiece) for such a crossover.

Knowing exactly what is going on is also the reason why I would prefer a direct convolution to a FFT one., even if the later *can* be made as good (good enough) as the former...

Last edited by pos; 5th January 2013 at 02:18 PM.
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Old 5th January 2013, 02:30 PM   #252
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I am getting the Truextents for Radian 1 inch drivers. These will not come close to any PCs or Behringers :-)
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Old 5th January 2013, 02:59 PM   #253
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what is the MTBF of a eval. board pushed to the limits ?

8 long straight convolutions during hours will be a good test.(under max thermal limit).
a good power supply and fan added should increase lifetime/failure.

IMHO,wise way is to use IIR Xover and a FIR in front of.(or FFT conv. for high FR resolution and low cpu consumption ).

Last edited by thierry38efd; 5th January 2013 at 03:07 PM.
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Old 5th January 2013, 03:42 PM   #254
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Knowing exactly what is going on requires understanding that Fourier transform is gateway between time and frequency domains, theoretically no information is lost.

Losses to math noise are inconsequential next to transducer performance.

All convolution processing uses fundamental math found for numerical methods of producing Fourier transforms.
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Old 5th January 2013, 04:36 PM   #255
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How do you know how miniDSP (or any other manufacturer) will implement their FFT convolution?
I have had bad (albeit very limited) experiences with SIR, so I would prefer to stay with a direct, straight forward convolution if possible (even if that implies using several miniSHARCs, if they do not implement downsampling), and this will also give the shortest processing time for a given impulse length.
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Old 5th January 2013, 04:47 PM   #256
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Quote:
Losses to math noise are inconsequential next to transducer performance.
i think too.
during listening,with a "flat" IR loaded in the convlover,switching bypass has no effect on quality sound perceived.
loopback sound card measurement shows no more THD and IMD.(also partitioned FFT).

that's why i don't understand why direct convolution is better (except a huge cpu load+power supply+EMI).

a challenge to extract the best of a standalone DSP ?

Last edited by thierry38efd; 5th January 2013 at 04:51 PM.
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Old 5th January 2013, 05:01 PM   #257
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Thierry, have you tired SIR?

For one thing, as already said direct convolution will give the shortest possible "processing" time for a given impulse.
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Old 5th January 2013, 05:22 PM   #258
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Originally Posted by pos View Post
Thierry, have you tired SIR?

For one thing, as already said direct convolution will give the shortest possible "processing" time for a given impulse.
i've tried:
SIR v1.011
VSTconvolver
LeCab2 (till 65000 taps )

a very short one (the given impulse)
a capture from the excellent book linked before (about DSP)
chapter 18.3

Click the image to open in full size.

may a 200/300 taps IR in a direct engine is little faster than FFT engine.

i go to try a direct conv. to compare process time.
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Old 5th January 2013, 05:43 PM   #259
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Quote:
Originally Posted by more10 View Post
These will not come close to any PCs or Behringers :-)
I understand the fear of PC based crossovers (I've had the problem), but the Behringer? Never had one output what it was not supposed to, ever. You can set it wrong, but you can do that with a DSP board.

What's your experience?
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Old 5th January 2013, 05:51 PM   #260
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Thierry, I am talking about real elapsed time (delay), not CPU time.
In direct convolution with a hardware solution like the openDRC and a DAC, you can expect only a few ms of delay in addition to the "normal" delay implied by the impulse (depending on the position of the peak within the impulse).
A PC would already add some buffering delay for the soundcard, and some more if FFT is used...
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