How to measure phase properly at home using REW?

[Krunok]

Here are 2 graphs that may be of interest. It shows the phase response of the same filter with and without phase correction of passive crossover in the rePhase:

Taken from 10cm, without gating and FDW:

Taken from 0.5m (50cm), without gating and with FDW of 8 cycles:

It seems that measurement taken at 10cm better shows when passive XO has not been corrected.

It also seems rePhase is doing very good job in correcting phase of the passive XO.

 

[RayDunzl]

My only thought is to measure very nearfield...

No timing/gating trickery used, just default measurements in REW.

JBL LSR 308, someplace close, default (125/500) gating window, distance don't remember:

At the listening position the JBL shows the endless wrapping.


However, my MartinLogans can give a flat phase measure at the listening position -10 feet, default (125/500) gating, crossover from panel to woofer is at 180Hz):

 

[Dogan]

Well, I am not providing any instructions here - I described and showed how I measured phase in different ways and I'm seeking an advice from folks with more experience/knowledge to say which of these measurements can be trusted most.

Your response look fine to me but I don't really have the experience to judge how good it is. I would suggest you apply FDW of 8 cycles (for example) instead of right window gating and adjust scale to +/-360 degs so we can compare it more easilly with my graphs.

Well, I am not providing any instructions here - I described and showed how I measured phase in different ways and I'm seeking an advice from folks with more experience/knowledge to say which of these measurements can be trusted most.

Your response look fine to me but I don't really have the experience to judge how good it is. I would suggest you apply FDW of 8 cycles (for example) instead of right window gating and adjust scale to +/-360 degs so we can compare it more easilly with my graphs.

Here it is. The XO at 80 Hz is more obvious now.

Dogan

 

[Krunok]

My only thought is to measure very nearfield...

No timing/gating trickery used, just default measurements in REW.

JBL LSR 308, someplace close, default (125/500) gating window, distance don't remember:


View attachment 24749

At the listening position the JBL shows the endless wrapping.


However, my MartinLogans can give a flat phase measure at the listening position -10 feet, default (125/500) gating, crossover from panel to woofer is at 180Hz):

View attachment 24750

I know you said you don't remember but was the "very close" distance like 10cm or comparable to that?
My measurement taken at 10cm also doesn't require any gating.

Btw, it is well known fact that MLs were built using stolen Borg techology so they shouldn't be compared with the speakers produced with Earth technology.

 

[RayDunzl]

I know you said you don't remember but was the "very close" distance like 10cm or comparable to that?

I'm thinking like a meter or so, but out in the middle of the room with the speaker and mic on a pair of barstools.

That measurement is from December 2016.

I'm not building/modifying speakers so I primarily measure from the listening position, since that is where I, uh, listen, and for where any DSP mods are perceived.

 

[MZKM]

I am. But when you ask me for a practical advice how to setup your home WiFi network to be able to stream HD video I wouldn't send you scientific paper as you would probably have a hard time extracting practical advice to solve your problem from it unless you have some serious background in networking.

Seconded. Also, as someone who has a degree in Mathematics, I glanced at that paper and noped out of there, I’m too lazy to diligently read such a paper just to figure out how measure my speakers.

 

[daftcombo]

Well, the reasion why you've been told not to measure phase under 100 Hz is probably because there, there are phase deviations due to the microphone or the soundcard if both are not calibrated in amplitude AND phase.

For my ECM8000, I have 3 columns in the calibration file: one for frequencies, one for amplitude, one for phase. Somebody on a forum sent me his. I guess he made it by trying his mic on a properly phased system.

Here is the beginning of the file i use. You can see pretty dramatic changes (around 90 degrees) from 20 hz to 100 Hz:


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Yes, I would advise not to correct anything under 100 Hz if your mic is not calibrated. Even a 10 degrees difference is audible in that area. If you over-correct by 80 degrees for example, you get something probably awful!

What mic do you have?

 

[Krunok]

Well, the reasion why you've been told not to measure phase under 100 Hz is probably because there, there are phase deviations due to the microphone or the soundcard if both are not calibrated in amplitude AND phase.

No, it had nothing to do with microphones phase accuracy. It was stateed that "Please note that, in order to avoid generating pre-ringing, you should avoid correcting the phase bellow 100Hz, which is not useful anyway."
Here is the link to the article.

Btw, read this about ECM8000 calibration file.

I am using Dayton Audio iMM-6 calibrated measruement mic which came with it's own calibration file.
It is the same mic as UMM-6 but in a small casing and with TRRS interface instead of USB.

Even a 10 degrees difference is audible in that area.

There are many articles backed up with blind tests stating stating exactly the opposite, but let's leave that aside as that is not the topic here.

 

[Krunok]

Here are another 2 graphs showing the effects of rePhase correcting phase of the passive crossover:

Step response, 0.5m, no passive XO correction:

Step response, 0.5m, with passive XO correction:

I would say the difference is pretty drastic.

 

[Krunok]

My only thought is to measure very nearfield...

No timing/gating trickery used, just default measurements in REW.

JBL LSR 308, someplace close, default (125/500) gating window, distance don't remember:


View attachment 24749

At the listening position the JBL shows the endless wrapping.

I'm guessing this graph was measured after correction?
As you can see my phase graph is quite similar to the one of your JBLs. I'm also getting endless wrapping at LP.

I have concluded that 0.5m distance works best for me. It required FDW of 8 cycles but phase graph seems consistent and accurate.

 

[Krunok]

Here it is. The XO at 80 Hz is more obvious now.

Dogan

It looks fine now. Maybe you can try to unwrap it and reduce # of cycles to 7 or 6 if necessary.

 

[Krunok]

This also seen as a group delay offset (doesn't go to zero a high freq).

This is GD graph for ungated measurement taken at 0.5m. As you can seee it goes to 0 at HF.
This GD graph corresponds to phase graph from post #15

Adding FDW of 8 cycles fixes the wrapping of phase graph. Do you think that method is ok?

 

[daftcombo]

No, it had nothing to do with microphones phase accuracy. It was stateed that "Please note that, in order to avoid generating pre-ringing, you should avoid correcting the phase bellow 100Hz, which is not useful anyway."
Here is the link to the article..

It's maybe the only area where the phase corrections are audible. Really puzzled to read that they advise not to correct here!
Anyway, 90° with or without calibration in that specific area makes a difference. The guy who sent me the mic file is very serious, with electronic engineer school backround, etc. he is on a DIY forum. Not random posts on a forum.

Btw, read this about ECM8000 calibration file..

True that all mics differ but average corrections are still better than nothing. The best you could do would be to calibrate yours on a reference system with flat phase.

I am using Dayton Audio iMM-6 calibrated measruement mic which came with it's own calibration file.
It is the same mic as UMM-6 but in a small casing and with TRRS interface instead of USB..

Good but you need to get the file with the phase column. Ask for it to Dayton. They should sen it to you for your specific mic, with your unit number.

There are many articles backed up with blind tests stating stating exactly the opposite, but let's leave that aside as that is not the topic here.

If the tests are made for the 40 Hz - 150 hz area, link me please.

 

[daftcombo]

This is GD graph for ungated measurement taken at 0.5m. As you can seee it goes to 0 at HF.
This GD graph corresponds to phase graph from post #15

View attachment 24794


Adding FDW of 8 cycles fixes the wrapping of phase graph. Do you think that method is ok?

View attachment 24795

In my opinion, the rising in the 30-150 Hz range corresponds exactly to your mic phase deviation.

Your phase is flat, that's why any correction will sound worse.

 

[Krunok]

Anyway, 90° with or without calibration in that specific area makes a difference. The guy who sent me the mic file is very serious, with electronic engineer school backround, etc. he is on a DIY forum. Not random posts on a forum.

If that calibration file is not a result of precise measruement of your particular microphone (your own specimen) then I wouldn't rely on it.

If the tests are made for the 40 Hz - 150 hz area, link me please.

Just use forum search, it has been discussed here on more than one occasion.

You can also read this article, it provides many info about measuring speakers in time domain.

 

[Krunok]

In my opinion, the rising in the 30-150 Hz range corresponds exactly to your mic phase deviation.

Your phase is flat, that's why any correction will sound worse.

Take a look at the phase graph Ray posted in post #42 (upper one, for JBL). Don't you find it strange that his calibrated UMIK-1 is showing similar "phase deviation"?

 

[daftcombo]

How do you know it is calibrated in phase?
The point of calibrating is to have a flat curve when recording a flat system.

 

[daftcombo]

Come on, you wrote that correcting the phase in the bass department sounded "awful". Then you wrote that a lot of ABX showed that you couldn't hear a difference. What's the truth?

 

[Krunok]

Come on, you wrote that correcting the phase in the bass department sounded "awful". Then you wrote that a lot of ABX showed that you couldn't hear a difference. What's the truth?

M8, chill a little, you've stated your opinion so no need to bombard this thread.

 

[daftcombo]

Yes, I'm curious of other people opinion too. As I wrote before, I am not a specialist.

But the "you should avoid correcting the phase bellow 100Hz" is nonsense. People who build their own speakers need to measure the phase in the bass frequencies too, and set it in a way or another. It is not just about "avoid correcting" commercial speakers.
Perhaps that area needs a special treatment. I also read that under 300 Hz, people should correct to have minimal phase and not linear phase in order to avoid pre-ringing. I for one have better results with linear phase set with a calibrated mic.