Understanding sweeps and measurments

[ErikG]

ignore for now, something is wrong…

When using REW regardless of mic used (UMIK1v2 and BeyerDynamic MM1 both at 48kHz) I get varying low end (under 200Hz) measurements in a way I find very troubling.
If I run a series of sweeps the measurements in the low end differ too much between identical sweeps (mic in a fixed position, I am placed very still at the same position relative to mic and speaker for each measurement.

Is this normal?
Perhaps influenced by sample rate?

As I decrease the smoothing the difference it is becoming more apparent. Thus I question wether the measurement/REW is correct, the mic is correct, or I am not looking at this the right way...

I mean I want to see where any issues are in detail in frequency so I can see if we have any structural low end issues remaining.
So in my mind I'd like to use the VAR smoothing as that gives me better detail in the low end showing me possible issues in the rooms response. But when multiple measurements differ in frequency and level when I look at VAR or fully without smoothing. I know without smoothing isn't "true" to the ear, but it OUGHT to be true to the measurement.

But when I run multiple measurements they are just varying too much for me to trust what they show.

Attached three identical measurements taken in a row, everything the same between them, only difference is the smoothing, chosen.

Measurements prior to any room EQ. This all started when I reacted to what the GLM alignment did on my Genelec 8351B speakers. I

Any thoughts on this?

 

[ErikG]

OK, so something is seriously wonky, with all measurements lately.

I’ll just have to figure out what.
when I checked the waterfall it looks like I have some very serious ringing gong on, like 2,5 seconds, and that is not the case, it’s a pretty snappy small room, so I guess something has gone totally haywire with how my Mac or REW interprets these measurements. And maybe that also relates to why I get different results when doing multiple measurements.

so ignore original post for now.

 

[John Mulcahy]

When you'd like some input on the data best posting an mdat, easier to see what might be going on with the file.