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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 20th October 2018, 03:58 AM   #2551
DickLai is offline DickLai
diyAudio Member
Join Date: May 2018
Originally Posted by BYRTT View Post
Agree what pos hints and looking your mdat file shows some user stuff had to been understood in the long run, observed is IR (impulse response) which is ground for calculate phase is not alligned on timeline and actual about 11mS too early so for that use "Estimate IR delay" after each measurement or redo it for that mdat session you shared, also IR is inverted as far i can see so either invert it each time a new measurement has been done or go to "Preferences/Soundcard/Input Options" and tick on "Invert" so that any future measurements is inverted automatic. Info tells sweep is 2-200Hz lenght 256k and samplerate is 3000Hz, play around with these settings and mayby go a bit higher and think even a full bandwidth sweep will work, and that 3000Hz sample rate number sounds strange is that because source and output is listed as ASIO4ALL.

When pos talks minimum phase EQ also called IIR filter in digital domain he talks normal EQ as we know from analog gear and all EQ manupulation into REW is of minimum phase type, try understand normal our enviroment and musical instrument sound plus analog recording and reproducing gear is all of minimum phase type where phase pattern is predictable and follow amplitude domain, therefor if we EQ for example any non smooth amplitude error we also automatically repair phase, the confusing thing is probably in digital world we can also use FIR filters that can be either setup to behave as a minimum phase filter correction but it can also manipute phase on its own. In general use always IIR filters for any correction of a band pass and use only pure phase correction to repair if any real summing IIR XO point filters is used in system. In REW you can tell it to "Generate minimum Phase" and that trace show the phase that belongs to the measure amplitude and deviation relative to your measured phase is called excess phase and can for example be because measurments chain units is not calibrated or also in a acoustic domain measurment there can be tons of reflection that all sums or cancel into amplitude domain provided if they in perfect timed phase or some delayed cycles phase at arival time or out of phase. Try open your chart 10 again and "Estimate IR delay" as many times until dialog tells its at zero then "Generate minimum phase" and now see how phase for that measurment should have looked if it was perfect without any excess phase from non calibrated chain units and acoustic reflections. A help for acoustic reflections is adjust the time window especially at these low frq, try set "IR Windows" to FDW (frq dependant window) 6 widths in cycles before doing any EQ should help for filter out some reflections and not overdo EQ.

Other help can be generate textbook target files in Rephase as IR and import to REW so as to have some textbook graphs to look at and learn from, example is below where a band pass BW2 at 20Hz - LR8 at 100Hz was set to replicate something close to your curves.

From over here software the below attached pdf white paper should be good reading for frq as low as these also because frq is so low it should be possible using white papers nearfield method to set a perfect band pass at enclosure location and then via the shared spreadsheet over there called "Baffle Diffraction and Boundary Simulator v1.2" calculate and export a frd file to Rephase to be reverse EQed so that room nasty gain problems is corrected for.
Thanks a lot for your reply.
I am a newbie in using REW and EQ tools, reading a lot of related articles and trying to understand what has happened to my system and trying to fix them.

Yes I am using ASIO4All to do measurement, and using lefft speaker as reference timing to measure the subwoofer.

I will try the raw measure again with your suggestion and correct the inverted IR and align the time before posting it again.

Thanks for sharing the readings, it is very useful.

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