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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 28th October 2016, 05:03 PM   #1231
FoLLgoTT is offline FoLLgoTT  Germany
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@pos
Great work! Ist it possible to add 64 bit IEEE-754 format? BruteFIR doesn't seem to like the 64 Bit float WAV format.
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Old 28th October 2016, 08:09 PM   #1232
pos is offline pos  Europe
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nyt, thank you for the bug report

FoLLgoTT, good suggestion, thank you, I will send you a link to a 1.1.1 release candidate including a 64 bit IEEE format, if you can find some time to test it!
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Old 28th October 2016, 11:55 PM   #1233
SwissBear is offline SwissBear  Switzerland
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Quote:
Originally Posted by pos View Post
I plan on releasing it very soon to avoid misunderstanding from spreading, so if you have encountered bugs or typos, or if you have suggestions that can be easily implemented please tell me ASAP
Hi Pos,
- not sure it is a bug, but the directory in which the impulses are generated is not saved as part of the config file. So it has to be changed every time a modification is made
- for future versions:
- if you could use one run of optimization to generate multiple impulses with various sampling frequencies, it could be useful
- also, if you could import sets of amplitude corrections (gain EQ) from REW, (which has all the mechanics in place to generate this set of corrections to match a target curve), it could help avoid the manual entry of these corrections. This does not save the fine tuning of the curve inside rePhase; but helps using the optimization included in REW for this purpose.
- finally, I have considerably reduced the pre-ringing of my correction impulses trying to stick to the minimum phase curve related to the amplitude. Would it be possible to have the option to display this minimum phase curve in real time inside rePhase, to help this manual tuning ?
Thanks

Last edited by SwissBear; 29th October 2016 at 12:09 AM.
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Old 29th October 2016, 11:01 AM   #1234
SwissBear is offline SwissBear  Switzerland
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A quick illustration of the importance of sticking to the minimum phase in the low range to limit pre-ringing:
- two graphs before optimizing the phase response in the low range: the pre-ringing is quite substantial
- two graphs after optimizing the phase response to stick to the minimum phase curve: the pre-ringing has massively decreased
All charts with the same amplitude curve.

What remains to be sorted out is the divergence with minimum phase in the high frequencies range. May be related to the absence of mic phase calibration. Any suggestions welcome.
Attached Images
File Type: jpg Phase Comparison Before.jpg (203.7 KB, 188 views)
File Type: jpg Step before.jpg (157.5 KB, 179 views)
File Type: jpg Phase Comparison After.jpg (204.8 KB, 179 views)
File Type: jpg Step after.jpg (151.8 KB, 176 views)

Last edited by SwissBear; 29th October 2016 at 11:03 AM.
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Old 29th October 2016, 01:18 PM   #1235
skyunlimited is offline skyunlimited  Germany
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Hey Pos, if possible i woud like to test the 64bit Files in Brutefir too.

Regards
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Old 29th October 2016, 01:48 PM   #1236
pos is offline pos  Europe
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Hi SwissBear,

Thank you for the suggestions!

Quote:
Originally Posted by SwissBear View Post
- not sure it is a bug, but the directory in which the impulses are generated is not saved as part of the config file. So it has to be changed every time a modification is made
The directory part is dependent on your particular directory layout, and should not be saved in the settings.
The filename should not either, but it is, for historical reasons...

I will probably try to rework all this in a future release, and have the user choose a destination file *after* the generation process.

I would have to rethink a few things about the ergonomic principles at play though, as right now not only the filename but also the format is part of the settings, and that can be convenient at time.

The "noise floor" of the result curves also shows the real noise floor implied by the output format...

Well, I will have to think about all this some more.
Quote:
- if you could use one run of optimization to generate multiple impulses with various sampling frequencies, it could be useful
I can see your point!
This could be addressed by the above suggestion, if the user can save a given FIR several time, choosing a different format each time.

Quote:
- also, if you could import sets of amplitude corrections (gain EQ) from REW, (which has all the mechanics in place to generate this set of corrections to match a target curve), it could help avoid the manual entry of these corrections. This does not save the fine tuning of the curve inside rePhase; but helps using the optimization included in REW for this purpose.
Good suggestion again.
AFAIK there are several "profiles" to choose from in REW when generating the automated EQs, encompassing a number of usable EQ points, types (shelving, constant Q, etc.), parameters (BW vs Q, etc.) and limits (dB range).
When I looked into this a few months ago I found one "profile" that was close enough (17 EQ points max, only EQ, ideal to fit one paragraphic EQ bank).
I will have to look it up again. The ideal solution would be for REW to implement a rePhase profile

Quote:
- finally, I have considerably reduced the pre-ringing of my correction impulses trying to stick to the minimum phase curve related to the amplitude. Would it be possible to have the option to display this minimum phase curve in real time inside rePhase, to help this manual tuning ?
Thanks
Extracting an accurate full range minimum-phase curve is not as easy as it looks. And once you have it why not simply automatically apply the phase correction?
I don't think I will implement this feature, as you should not really need it if you start with minimum-phase EQs, adressing both magnitude and phase linearization, and then only apply phase linearization (preferably from the filter linearization tab) for the crossover points (not the system's high and low pass filters).

Quote:
Originally Posted by SwissBear View Post
What remains to be sorted out is the divergence with minimum phase in the high frequencies range. May be related to the absence of mic phase calibration. Any suggestions welcome.
You should play with measurement time offset to get a proper phase there, and not try to linearize anything that is outside of the scope of a crossover point.
Regarding the phase response of your mic, if it is not included in the calibration file you can try to "resynthesize" it using the measurement "compensate" (soon to be called "invert") functionality as explained above.
I did so with mine (coming from cross spectrum with no phase info) and I found it worked pretty well.
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Last edited by pos; 29th October 2016 at 01:55 PM.
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Old 29th October 2016, 04:38 PM   #1237
SwissBear is offline SwissBear  Switzerland
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Thanks for your detailed answer Pos. Will continue learning
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Old 29th October 2016, 04:52 PM   #1238
diyaudnut is offline diyaudnut  United States
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Hi pos, is the internal processing precision along updated to 64bit?
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Old 29th October 2016, 06:01 PM   #1239
pos is offline pos  Europe
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Quote:
Originally Posted by diyaudnut View Post
is the internal processing precision along updated to 64bit?
yes
And guess what: it always was
The txt output format, for example, always had 64 bit double precision.
I don't know were I got the idea that the FFT library I was using was working with 32 bit float precision
It is a library called fft4g, written by Takuya OOURA in 1999.
I also recently tried the industry standard FFTW, but could not record any difference in precision, or any significant/consistent speed gain.
FFTW has other advantages though, so I will pursue my tests with it...
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Old 29th October 2016, 06:12 PM   #1240
diyaudnut is offline diyaudnut  United States
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Quote:
Originally Posted by pos View Post
yes
And guess what: it always was
The txt output format, for example, always had 64 bit double precision.
I don't know were I got the idea that the FFT library I was using was working with 32 bit float precision
It is a library called fft4g, written by Takuya OOURA in 1999.
I also recently tried the industry standard FFTW, but could not record any difference in precision, or any significant/consistent speed gain.
FFTW has other advantages though, so I will pursue my tests with it...
Thats great . Thanks.
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