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Multi-Way Conventional loudspeakers with crossovers

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Old 1st January 2013, 10:58 PM   #181
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Quote:
Originally Posted by Pano View Post
OK, but if it's a "perfect impulse" (1 sample on, all others off) it should do nothing, right?
Don't forget to make sure the amplitude response over 20 - 20k Hz is matched to better than 0.1dB for the two impulse responses.
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Old 1st January 2013, 11:27 PM   #182
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Originally Posted by john k... View Post
Why? Because you don't know what the effect of the convolution engine is. Yes a perfect impulse should do nothing but which is why it's a good check on whether the convolution engine introduces any artifacts of its own.
you're right,i've been traped several times.
that may leads to wrong conclusion.

with jriver,send a sine at 1 or 2 kHz,check the level and adjust with/without convolution.(with yours ears)
once adjusted,try with musical file.
vsthost allows more flexible adjustemnt in this way but level must be matched perfectly.

Last edited by thierry38efd; 1st January 2013 at 11:43 PM.
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Old 2nd January 2013, 12:43 AM   #183
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I tried it with a perfect impulse and no impulse. Same to my ears. I'd have to measure or use the diffmaker software to tell if there is a difference. I'll try that.
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Old 2nd January 2013, 04:43 AM   #184
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Originally Posted by kgrlee View Post
The off axis vertical impulses show loadsa pre-impulse as expected and discussed by Greenfield.

You'll excuse me my old fashioned prejudice as a commercial speaker designer for more than half my life, that finds pre-impulse evil except for certain anti-aliasing filters.
An impulse response is complete characterization of system, the IR doesnít have a pre-impulse; this is confusing a causal source of information with the transmission of information. IR of transmission system describes what will happen to information that is being transmitted through the system via convolution.

As old fashioned speaker designer, self interested prejudice against tools that flatten the playing field is understandable, but is not an excuse for calling time domain behavior of linear phase filters with frequency dependent amplitude evil.

You see the sense with anti-aliasing filters. See the rest of it.
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Old 2nd January 2013, 04:50 AM   #185
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Originally Posted by Pano View Post
What will that sound like? Will I even hear it? Time will tell.

Hi Pano,

This may be helpful to you.

http://www.bodziosoftware.com.au/Att...udspeakers.pdf

Best Regards,
Bohdan
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Old 2nd January 2013, 08:04 AM   #186
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example of 3 impulses responses

a acausal one,centered at t=0,and two causal shift in time.

Click the image to open in full size.

phase resulting,note the linear X axe.

Click the image to open in full size.

Click the image to open in full size.
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Old 2nd January 2013, 10:11 AM   #187
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Originally Posted by Barleywater View Post
An impulse response is complete characterization of system, the IR doesnít have a pre-impulse; this is confusing a causal source of information with the transmission of information.
I think what is being referred to is the effect of summing of axis. At linear phase filter has pre-ringing. But the sum of a HP and LP, at the design point, sums to a perfect impulse. As you move off axis the times of flight for the woofer and tweeter become different and the sum is not longer a perfect impulse. This reveals the pre-ringing, typically in the tweeter's impulse.
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Old 2nd January 2013, 10:22 AM   #188
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Here is an example of the effect of moving off axis for a linear phase LR4 type crossover and a normal. causal LR4 crossover. I've posted this figure many time in the past.

Click the image to open in full size.

The upper trace in each plot if the input or reference impulse. The lower trace is the measured impulse at the positions indicated. The upper set of plots is for the linear phase system, the lower set for the normal LR4. What you see, particularly in the 15 degree vertical plot, is the development of the pre-response of the linear phase crossover. Of course, it can be argued that with a normal crossover the tweeter response always leads the woofer.
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Old 2nd January 2013, 12:34 PM   #189
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Hi John,

In above, what is spectrum of reference? And what are driver diameters, what is vertical spacing of acoustic centers, and what is crossover frequency?

Edit:
Sorry, see fine print: 2kHz, but spacing?

And, on axis response should return reference for linear phase conditions, but doesn't, indicating error in level matching. Almost looks like polarity reversal.

Last edited by Barleywater; 2nd January 2013 at 12:57 PM.
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Old 2nd January 2013, 01:11 PM   #190
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Just add coffee. Top plots.....
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