How to measure phase properly at home using REW?

[JohnPM]

Probably some monitoring active on the "mains" outputs, meaning some of the input signal is being routed back to the outputs. Monitoring must be completely off.

 

[Digital_Thor]

When is measuring with a frequency depending windows better than doing it gated?
I know that a gated measurement is limited by the first reflection - but I should think that it gives me a more precise result, than trying to capture my speakers output from the listening position. Especially since I'm only able to EQ speaker issues - not the room.

 

[mamba76]

When trying to do room EQ measurements with REW you will find a lot of information on the Net. You have option to do RTA measurement with pink noise using moving microphone method. Another option is to make several sweeps at and around your LP and use "Average the response" feature under All SPL tab. If you want to preserve timing information you can rely on a single sweep or use Vector average (although that one tends to result in a weird frequency response, but there you have it).

However, with phase measurements things are getting a little tricky. let's assume for simpicity you have a done a single sweep and that it contains accurate info. You fixed the IR delay and your phase is shown wrapped in REW. But what now?

At the very beginning you will soon realise that it gets much harder to get phase response displayed correctly in REW as your distance between microphone and speaker gets bigger. If you measured from 10cm distance chances are you would not need to apply any gating and/or frequency dependent windowing to show pahse correctly.
If you measure from 0.5m or 2m you will probably need to make some adjustments under IR Window settings to get the phase displayed properly. But if you measure from your LP whivh is say 4 meters from your speakers and reflections in your room are pretty high you may realise that displaying phase correctly presents quite a challenge.

This is how it looks when I do it in my room with my left speaker, measured from app 2m, no gating:



With right window of 3ms (doesn't display correctly with higher value):


With FDW of 3 cycles (doesn't display correctly with higher value):


Here I would like to say that when I measure phase from 10cm no gating nor FDW is required to display phase correctly. As measuring distance increases the reflections are building up so I have to apply more and mroe gating to display phase.

Phase overlayed (3ms vs FDW 3cycl):


Step overlayed (3ms vs FDW 3cycl):


GD overlayed (3ms vs FDW 3cycl):


So, after all of these graphs a few question arises, like for example:

- what is the optimum distance to measure phase in your room? Very close to the speaker, say 10cm, or at your LP?
- what is the optimum way to adjust your measurement? Applaying right window time gating, FDW, or both?
- should we even bother with all this? Does getting the phase flat matters at all?

I would like to add here that, when i wasHi doing manual correction of my room/speakers response I didn't rely much on measuring uncorrected phase response. Once I fixed amplitude response in rePhase I corrected phase of my filters so it would be as close to 0 as possible to stay minimum phase and I entered data about my crossover (LR 24dB/oct at 1800Hz) so the rePhase can take it into account. The graphs above are showing the results of that.

Hi. Please show me how you get REW to overlay the phase and frequency response? The first picture is shown phase unwrapped then you changed right IR window to 3ms - is that phase or FR we are looking at. Im messing about with more interest the phase info REW offers and cannot get the data displayed the way some people can (like the rephase vid on youtube). Can you provide a walk through or steps to set REW for this display from default settings. Hope this makes some sense. Thanks

 

[CauliflowerEars]

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.

Would you say the Dayton Audio IMM-6 is good enough for room acoustic measurements for room treatment?
Or better get the ECM8000 or even UMIK-1 / Dayton Audio UMM-6?
The ECM8000 would also need an interface, bringing the costs up to the UMIK-1 level anyway ...

I'm just getting into my living room measurement and not sure what's enough. Would prefer to spend the money on the treatment and/or upgrading the system.