REW measurement with loopback reference

Hello

I dont understand why measuring with a feedback - reference loop REW measures unreadable phase data. On the contrary, with no timing reference it measures a nice looking phase response.

Screen Shot 2023-03-05 at 12.37.15.png




Screen Shot 2023-03-05 at 12.37.35.png


No reference
Screen Shot 2023-03-05 at 12.38.02.png



with reference
Screen Shot 2023-03-05 at 12.38.58.png


When I do a sound test, the levels indicate the mic is on the measurement tab and the loopback is on the reference tab.

Thanks
A