Using REW and rephase to generate amplitude and time domain corrections

[89reksal]

I'm trying to follow along with SwissBear's pdf tutorial linked above in this thread. I'm having a problem with convolving the rePhase correction impulse to my REW measurement. When I do the convolution with the settings shown (A*B) I end up with a new measurement at 152.9 dB, which is about double the original measurement. At this point, I don't know whether this is wrong (I'm assuming it is) or if it's ok how to I work with it at such an increase amplitude.

 

I've attached a screenshot that should help explain better.

 

Thanks in advance for any help.

[89reksal]

Thanks SwissBear. I assume I do that adjustment in the same window as the convolution? Using the "offset data" setting? That's how I've done it for now.

[89reksal]

Thanks SwissBear.

[89reksal]

I'm having a problem following along with SwissBear's guide. I think I've done the first 3 steps ok, but I'm lost on step 4. which reads as follows:

 

"4. Correction finalization
Once you have finalized the phase correction, you can import the initial averaged
measurement in rePhase and apply the REW filters. The result could look like this:"

 

I'm reading "Once you have finalized the phase correction" to mean once I have finished the phase correction in rePhase on the convolved (A*B) extended phase created in step 3. 

 

This part "you can import the initial averaged measurement in rePhase and apply the REW filters" has me lost. What do I do with the phase correction I just completed on the extended phase (shown in screenshot below)? Am I supposed to leave that as is in rePhase and now import my measurement that I eq'd in REW into the open window in rePhase that currently has the corrected excess phase with all settings from that phase correction? I'm sorry for the dumb questions but I'm pretty much lost at this point. I read the full 237 pages from the DIY thread but most of it seemed to be more focused on working with individual crossovers and I wasn't able to find an answer.

 

I've also included my original measurement files for left and right speakers in case they're of any use:

 

LR_Original.mdat.

 

These were initially done in Audiolense and imported into REW.

 

Thanks,

 

Bill 

 

 

[89reksal]

Thanks pkane2001. I ended up figuring it out and getting a filter working. I'm quite happy with the result, especially as a first attempt. I do have a few additional questions.

 

1) I'm wondering what the reason is for using a flat target in REW for the EQ (Speaker Type = None, instead of Full Range)

 

2) my excess phase generated from convolving A*B is a flat horizontal line from low to upper hf limit where it falls off at 90 degrees. It would seem there should be some kind of deviation from flat otherwise there is no excess phase to correct? Does mine sound correct?

 

3) once I have the excess phase corrected for phase in rePhase, I then load in my original measurement to apply the saved eq amplitude filter. As soon as I load the measurement, before applying the REW filters, the corrected phase in rePhase shifts up, maybe 90 to 180 degrees. Does that sound normal? Should I be readjusting the phase to correct for that shift before generating the final impulse?

 

4) My original measurement is 48k. I'm using jriver for convolution. Can I just change the rate in rePhase Impulse Settings to 44.1, 88.2 and 96 to create impulses for each sample rate I want to use in jriver, using the same 48k measurement and corrections? (My dac only goes up to 96k). That means I'd have to generate 8 impulses to make my 4 .cfg files for jriver convolver.

 

5) For my first attempt I did separate left and right channel mono corrections for phase (not using same correction for both channels). I read some discussion on using same phase correction for both channels. I'm wondering if there's a real preference on mono for each channel or same correction for both.

 

Thanks.

[89reksal]

Thanks pkane2001. 

 

54 minutes ago, pkane2001 said:

That doesn't sound right. I found that there's very little phase to correct with my headphones, but with my speaker system there were very large deviations. I suspect that you need to use REW to measure. Don't know much about Audiolense, but it looks like phase is either not being recorded or is not being imported correctly in REW.

 

I'm definitely getting phase information in my measurement so I'm pretty sure it's not an issue with the measurement. Just to clarify, I'm generating the excess phase directly from the convolved A*B measurement from Step 3 in SwissBear's guide. Is that the correct procedure? No need to generarte a minimum phase first? I'll redo to double check the steps I followed.

 

1 hour ago, pkane2001 said:

Wait.. I apply the PEQ filters only (not measurement) to the phase-corrected curve. I don't reload the amplitude corrected curve at that step.

 

It seems like I'm still not clear on this step then. It sounds like you're saying you apply the PEQ filters to the same measurement (excess phase of A*B) that you did the phase adjustment on in rePhase.  Here's the description from the guide step 4 (bold added by me):

 

"4. Correction finalization
Once you have finalized the phase correction, you can import the initial averaged
measurement in rePhase and apply the REW filters."

 

From that, I took it to mean that once I do the phase correction on the excess phase, then by using those settings on the initial averaged measurement which was imported into the same window as the excess phase measurement with same settings, in rePhase, I then import the REW eq settings (.xml file) for the PEQ correction, which together with the already loaded phase correction settings from the excess phase correction, gives the frequency and phase corrected impulse for that initial averaged measurement. In my case it's not an averaged measurement, it's the measurement imported from Audiolense. I'm just using the "initial averaged measurement" term to be consistent with the guide. Hopefully you (or anyone else) can see what I'm doing wrong, assuming my procedure is wrong.

 

Thanks again for taking the time to respond.

[89reksal]

Thanks. I'll go through everything again and see if I can figure out what's going on with the flat excess phase measurement. Even with the correction as I did it, compared to the frequency only corrections I did in REW, the improvement with the added phase correction is definitely noticeable. Well worth the time invested.

[89reksal]

22 hours ago, pkane2001 said:

I just looked at your measurements file. It appears that you've imported the data as an impulse response into REW? Can you try importing as a frequency response?

 

When I use the export measurement function in Audiolense, the measurements are exported in .pcm format. From the REW Help section it looked like this was ideal:

 

"Full range ETF measurements allow the impulse response to be exported in a .pcm raw data format, using the File -> Write Impulse As *.pcm option. Use REW's File - Import Impulse Response command to load these files. Importing the impulse response allows REW's Spectral Decay and Waterfall plots to be generated from the data (this is not possible when importing frequency response text files)."

 

I didn't try importing as frequency response instead since I couldn't see how to get Audiolense to export in any other format than .pcm.

 

I tried a couple more run throughs with SwissBear's procedure and I always get the flat excess phase. After thinking about it more, I believe the flat excess phase is ok. The flat line is showing the amplitude of the excess phase, not the phase. I believe there shouldn't be any difference in amplitude between the excess phase and my amplitude corrected measurement, thus the flat line I'm seeing. The difference between the two is phase, which is what I'm trying to adjust for in rePhase.

 

On 11/21/2017 at 7:27 AM, lasker98 said:

3) once I have the excess phase corrected for phase in rePhase, I then load in my original measurement to apply the saved eq amplitude filter. As soon as I load the measurement, before applying the REW filters, the corrected phase in rePhase shifts up, maybe 90 to 180 degrees. Does that sound normal? Should I be readjusting the phase to correct for that shift before generating the final impulse?

 

As for the phase shifting once I load in the original measurement for final correction, that also seems normal. It would seem the shift is because the phase corrections from the previous excess phase correction are still loaded in rephase, which are now being applied to the original measurement, which is exactly what is intended to remove the excess phase from the original measurement. As for my last sentence about readjusting for that shift, I would say definitely not, since that would be adding excess phase back in.

 

SwissBear's guide is showing how to do PEQ on the original measurement in REW, then how to correct the original measurement for excess phase only in rePhase, then applying that excess phase correction and the REW PEQ to the original measurement in rephase to create the impulse used for convolution. It's quite an elegant approach imo, since instead of looking at the phase of the original measurement and trying to figure out how and what to correct, we're working only on the excess phase, which is exactly the phase component we want to eliminate to end up with as close to minimum phase as possible.

 

Thanks again to all for your help.

[89reksal]

That would be great. Thank you.

[89reksal]

Very odd. That looks more like eq'd measurement before anything in rePhase. Here's screenshots of my full REW graphs window. You can kind of see the shapes in the thumbnails in the left sidebar. I've also included the excess phase as imported into rePhase prior to any corrections being applied (phase or frequency). I'm using 6 cycles FDW and psychoacoustic smoothing for the REW EQ.

 

 

 

[89reksal]

Here they are:

 

_09 _measurements.mdat

[89reksal]

Just a note for clarification on those measurements. The Left_original and Right_original are the imported measurements from Audiolense that were in the previously posted .mdat measurement file. They have no windowing or smoothing when imported, that's applied after importing into REW. 

 

In the .mdat file I just uploaded, those have the 6 cycles FDW and Psychoacoustic smoothing applied, as they were used in auto generating the REW EQ filters.

[89reksal]

That's much closer for sure. I appreciate you taking the time to look at my measurements. Would you mind posting the measurements you did to end up with the excess phase you posted? I'm very curious about what you did to get the one dip around 270 Hz.

Thanks.

[89reksal]

There's something odd going on. I load your measurements and see the dip on the "A times B-EP" ( I renamed it to "R_A tmes B-EP" so I was able to make new ones), although the dip is much less than on the screenshot you posted Wednesday. I generate a new "A times B" using the exact same Right_original and R-amplitude_09 and then from that generate a new excess phase version and the result is completely flat. I have no idea why we're getting different results using the same measurements. I'm using REW V5.19 Beta 7 in case that's different from the version you're on. I'm also running Windows 10.

 

I'm attaching my measurements which are the ones you uploaded plus the newly generated A times B and A times B-EP which were created the same as you originally did on the ones I renamed.

 

pkane_dip_02.mdat