Dear Rich,
thanks for your time in taking all those measurements, I appreciate and thank you
Actually the measurements in the range of from 20 Hz to 400 Hz show the same results...
at first sight one may think differently when looking at your graphs as your graph appears to be much smoother.
You may be inclined to believe that it is more accurate also because you mentioned that you are satisfied with your results without correction.
I have cut your Dirac graph so that it shows only the region of frequencies from 20 Hz to 2 KHz within a range of 50 dBs... here it is:
We then have to compare it with your other measurement, but in order to compare it we need to normalize it so that we are looking at it with the same scales and proportions... so your other graph here now shows the same 50 dBs range and the image has been properly scaled so that it is directly comparable.
Here it is...
Now one can clearly see that the behaviour is the same up to 400 Hz, the two measurements are consistent and you may even recognize the individual channels.
So there is no conflict in the measurements in the low frequency range up to 400 Hz while your other measurement shows a sizable dip after 1 KHz...
(others follow as in the past if we look at your full bandwidth graph)
Dirac's measurements, if properly taken and the mic calibration file is an individual one, are accurate... their validation has been discussed for example here:
http://www.computeraudiophile.com/f23-dsp-room-correction-and-multi-channel-audio/dirac-lives-graphs-how-accurate-23086/
My two cents as usual,
Flavio