Great before and after posts on Dirac! I've seen similar impressive before and after results in my system under Trinnov, as measured by both the frequency and impulse response plots generated by REW.
Do you get time/distance measures and also phase measures, like in REW, even without a loopback? I thought the loopback was required to get a consistent timing reference.
Loopback would only be needed to correct the device's FR or to get absolute time values. There's no need to for a timing reference with any of these measurements I have posted. Yes, fuzzmeasure does give absolute time value measurements. Here's a video explaining how it works in fuzzmeasure: