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Multi-Way Conventional loudspeakers with crossovers

rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
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Old 5th April 2017, 09:47 PM   #1851
sax512 is offline sax512
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Originally Posted by torgeirs View Post

The discussion is when two highorder filters that IS timeshifted (different distance to each speaker element) will generate clearly audible artifacts.
Got it. But that's not a problem of pre-ringing, as indicated by many by the pre-peak part of the impulse response. Again, it's probably worth repeating, those pre-peak ripples are SUPPOSED to be there.

You're talking about two drivers producing the same range of frequencies and the artifacts that result.
I completely agree with you and that's why after listening to my first full range I never went back to 2 or more ways speakers.
Still, it is a completely different thing.

I think what most people have a hard time to grasp is that a Dirac impulse excitement as input to a brickwall filter, ideally, SHOULD produce an infinite output waveform.
I'm also convinced this is closely related to the fact that people think of a brickwall filter as an interpolator, while it is nothing like that. It is a device that adds sinc functions that are proportional to the samples at its input.

Last edited by sax512; 5th April 2017 at 09:50 PM.
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Old 5th April 2017, 09:48 PM   #1852
mark100 is offline mark100  United States
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rePhase, a loudspeaker phase linearization, EQ and FIR filtering tool
Ok, let me add a followup question after reading further posts...

The time shift being discussed...where exactly is it coming from?

(I know even tiny shifts of a couple of samples, 0.04ms, of pure delay, are easily audible at 6300hz, with pink noise tuning a bms coax CD.)
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Old 6th April 2017, 06:52 AM   #1853
wesayso is offline wesayso  Netherlands
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Inter driver distances when moving off axis.
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Old 6th April 2017, 07:30 AM   #1854
torgeirs is offline torgeirs  Norway
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Originally Posted by mark100 View Post
Hi, I'm having trouble following along...
What do you mean by one filter is time shifted?

Doesn't proper time alignment mean both filters stay in sync (phase) throughout crossover overlap?
I must be missing something, because I know 1ms is a gigantic time misalignment between drivers.

Do you maybe mean 1 ms worth of latency, eg say using complementary LR FIR filters, both side of crossover with 48 taps at a 48kHz sampling?
Or maybe the LPF is using 96 taps, and the HPF 48 taps, for a net 1ms difference between passbands, that needs be offset with delay elsewhere?

I guess I'm asking how can you shift only one filter?
What I was trying to say was that i doubt there will be off axis artifacts with a 24dB/oct filter. Analog, IIR or FIR. With artifacts I mean sounds that is heard as seperate noiselike sounds.
And, yes, its the difference in pathlength. Of course also both filters are shiftet in time as you sit away from the speakers:-)
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Old 6th April 2017, 07:39 AM   #1855
wesayso is offline wesayso  Netherlands
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As an exercise, create a perfect Dirac pulse in RePhase and import it in REW. It wil look like that straight pointy thing. Now shift it in time in REW (controls: t=0 offset). See how there's ripple both in front and after the pulse? Does this mean if I press play too late I get pré ringing?
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Last edited by wesayso; 6th April 2017 at 07:55 AM.
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Old 6th April 2017, 07:42 AM   #1856
torgeirs is offline torgeirs  Norway
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@Sax512: I think it is interesting to see how ringing interacts when combined with a time shift. The finnish paper show that there can be very small changes in frequensy response, 0.1 dB, and still artifacts can be heard. So I still believe the time response is the reason.
(The time response do not look as an dirac at all, asymetric, huge sidelobes, not uniformly falling sidelobes etc., So we are not talking small ripples here)
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Old 6th April 2017, 07:52 AM   #1857
torgeirs is offline torgeirs  Norway
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Quote:
Originally Posted by wesayso View Post
As an exercise, create a perfect Dirac pulse in REW. It wil look like that straight pointy thing. Now shift it in time in REW (controls: t=0 offset). See how there's ripple both in front and after the pulse? Does this mean if I press play too late I get pré ringing?
My understanding is that rew shift the impulse response inside the window. Then it is not symetric anymore, and you have extra ripples
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Old 6th April 2017, 08:09 AM   #1858
jmbee is offline jmbee  France
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Originally Posted by torgeirs View Post
My understanding is that rew shift the impulse response inside the window. Then it is not symetric anymore, and you have extra ripples

As i see in Rew, it's a problem of extrapolation between samples. If the impulse is time shifted of an exact lenth of one or X samples, ringing desappears.
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Old 6th April 2017, 08:13 AM   #1859
torgeirs is offline torgeirs  Norway
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Ok, thank you for clearing that up. I was wrong about shifting inside the window.
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Old 6th April 2017, 08:21 AM   #1860
torgeirs is offline torgeirs  Norway
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Originally Posted by mark100 View Post
Ok, let me add a followup question after reading further posts...

The time shift being discussed...where exactly is it coming from?

(I know even tiny shifts of a couple of samples, 0.04ms, of pure delay, are easily audible at 6300hz, with pink noise tuning a bms coax CD.)
So the bms coax should not be affected by these effects if the drivers are perfectly time alligned and have same directivity at the frequency i question.
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