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Old 22nd May 2013, 04:41 PM   #401
pos is offline pos  Europe
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Quote:
Originally Posted by luigichelli View Post
what if someone wants to do an ABX test of the phase linear system again the minimal phase version?

if i drop by 6 dBFS both the filtered and the original signal it would not be fair since the filtered would peak higher... should i put a limiter after the convolution, to tame the peaks?
For ABX you should reduce both signals by the same amount of course.
The RMS level should stay the same with or without phase linearization: only peaks level will change.
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Old 22nd May 2013, 05:05 PM   #402
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From the EASY FIR thread :
Quote:
Originally Posted by soundcheck View Post
1. Acourate DRC seems to do rather successful preringig reduction.
People are pretty positive about that feature which was developed
not long ago after years of having that preringing i.

Is rephase taking any actions to reduce the FIR filter associated preringing??
Hi soundcheck,

I don't know what was implemented in Acourate, but to my knowledge any specific amplitude+target curve should result in the same IR (with potentially different windowing shapes and length, of course).

Preringing becomes apparent when you have a linear-phase LP or HP filter (or you linearize the phase of a minimal-phase LP or HP).
The steeper the slope, the more important the prerining becomes.

If you are designing a multiway crossover using convolution, prerinings from matched LP and HP filters (ie amplitude complementary and phase coherent crossover) will cancel each other (as long as the summation is good, so you better match your polar responses and keep your drivers within reasonable distances, especially if you are looking for steep slopes, but that is also true for classical IIR filters, where postringing can become very long...).

If you are also using LP and HP linear-phase filters or linearizing the phase of minimal-phase filters (electrical IIR, or from the box, of natural driver rolloffs...) at the extremities of your loudspeaker frequency range, then you will not have any complementary filter to cancel the preringing, and it might become apparent when looking at the IR.

rePhase is not an automated tool, so you can choose for yourself what to correct and what to leave alone, so for example if you correct the phase of a bassreflex for example you have to know that some preringing will result (audibility of which is another issue...).
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Old 22nd May 2013, 11:24 PM   #403
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Quote:
Originally Posted by pos View Post
From the EASY FIR thread :
Hi soundcheck,

I don't know what was implemented in Acourate, but to my knowledge any specific amplitude+target curve should result in the same IR (with potentially different windowing shapes and length, of course).

Preringing becomes apparent when you have a linear-phase LP or HP filter (or you linearize the phase of a minimal-phase LP or HP).
The steeper the slope, the more important the prerining becomes.

If you are designing a multiway crossover using convolution, prerinings from matched LP and HP filters (ie amplitude complementary and phase coherent crossover) will cancel each other (as long as the summation is good, so you better match your polar responses and keep your drivers within reasonable distances, especially if you are looking for steep slopes, but that is also true for classical IIR filters, where postringing can become very long...).

If you are also using LP and HP linear-phase filters or linearizing the phase of minimal-phase filters (electrical IIR, or from the box, of natural driver rolloffs...) at the extremities of your loudspeaker frequency range, then you will not have any complementary filter to cancel the preringing, and it might become apparent when looking at the IR.

rePhase is not an automated tool, so you can choose for yourself what to correct and what to leave alone, so for example if you correct the phase of a bassreflex for example you have to know that some preringing will result (audibility of which is another issue...).


Hi,

Pre-ringing and post-ringing are typically not an issue.

http://www.bodziosoftware.com.au/Pre...And_Pulses.pdf

Best Regards,
Bohdan
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Old 23rd May 2013, 08:25 AM   #404
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Hi there.

Until now I thought the ringing issues are one of the biggest ( and audible) issues associated to FIRs.

DRC also puts some effort on the ringing part. See DRC chapter 4.2.1. + 4.2.2


Cheers
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Old 23rd May 2013, 08:44 AM   #405
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Quote:
Originally Posted by pos View Post
you have to know that some preringing will result (audibility of which is another issue...).
Quote:
Originally Posted by bohdan1232000 View Post
Pre-ringing and post-ringing are typically not an issue.
Hi Bohdan
By "is another issue" I meant "is another question", and a question that does not belong in this thread I think.
It is a general question when dealing with FIR filters. rePhase is just a tool and tries its best not to enforce any practice or dogma by letting the user do what he wants to do, may it result in prominent preringing or not.
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Last edited by pos; 23rd May 2013 at 08:55 AM.
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Old 23rd May 2013, 08:52 AM   #406
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Quote:
Originally Posted by soundcheck View Post
DRC also puts some effort on the ringing part. See DRC chapter 4.2.1. + 4.2.2
It does so by applying special frequency-dependent windowing, and affects the resulting phase correction curves as a result (the fft of the correction impulse), towards a minimum-phase behavior on the ends of the passband.
It has to resort to this technique as it is an automated tool based on impulse inversion.
In rePhase you are in charge of the whole amplitude/phase target, so it is up to you to make these decisions.
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Old 23rd May 2013, 09:02 AM   #407
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[QUOTE=bohdan1232000;3501057]Hi,

Pre-ringing and post-ringing are typically not an issue.

http://www.bodziosoftware.com.au/Pre...And_Pulses.pdf

Bohdan[/QUOTE

Hello,

Among the different origins of preringing (sampling, linear phase crossover, etc.) there is one that is never shown in any documents it is due to the phase linearisation of the basss loudspeaker in the very low frequency domain inside which the loudspeaker behaves as a high pass filter (eg. 4th order for a bass-reflex).

Pano use to say that when he used to listen to a phase linearized system he felt that the attacks were somewhat less dynamics, blurred or strange ( sorry, I don't remember the exact words he used). Others emitted the hypothesis that this large preringing due to the low frequency cut off + phase linearization could be a source of "perceived like" intermodulation phenomenon when during an excerpt with a mid and high frequency content a pulsive note having a very low frequency content arrives suddenly.

What do people on DiyAudio you think of that?

I am not myself convinced through the experiments I have done by the benefit of complete phase linearization through the whole range of audible frequency (but I am in the mid frequency range).

Also, from my readings I acquired the idea that its is somewhat useless to linearize the phase at low frequency (someone said below 150Hz other one below 250Hz).

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 23rd May 2013, 09:16 AM   #408
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Quote:
Originally Posted by Jmmlc View Post



I am not myself convinced through the experiments I have done by the benefit of complete phase linearization through the whole range of audible frequency (but I am in the mid frequency range).

Also, from my readings I acquired the idea that its is somewhat useless to linearize the phase at low frequency (someone said below 150Hz other one below 250Hz).

Jean-Michel Le Cléac'h
Bonjour Jean-Michel,

Care to name a few of these sources?

Thanks!
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Old 23rd May 2013, 09:27 AM   #409
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Quote:
Originally Posted by pos View Post
In rePhase you are in charge of the whole amplitude/phase target, so it is up to you to make these decisions.

Being in charge and being capable (at least at this stage) are two pretty different things.
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Old 23rd May 2013, 09:32 AM   #410
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The implications and recommendations are pretty much summed-up in post #402 above.
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Last edited by pos; 23rd May 2013 at 09:37 AM.
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