can't be really a coincidence but probably be a systematic error.
The measurement is difficult and there are inaccuracies, but I think that the general trend is correct.
I repeated the measurement two times with near-field sweeps, and two times with mid-field MMM. Here are the differences (since each curve is a difference between two speakers, this is the result from 8 individual measurements) :
We can see a lot of variations on the purple curve, that should be perfectly identical to the blue one. They are caused by acoustic reflections on my body while I was sitting not far from the microphone, not paying attention to be in the exact same position.
The blue curve is cleaner because I was standing still at the exact same position, away from the mic, during the two measurements for this curve.
The comparison between both speakers measured 2 meters away with a moving microphone and a pink noise show a very different pattern. I can't explain this. I expect the sound level to be different between the two speakers, but not the geometry of the sound field !
But the two comparisons (red and green) give the same kind of result.
Same curves with 1/3 octave smoothing :
And here is the result of B over A vs A over B, calculated with no smoothing, then smoothed 1/24th octave, in order to evaluate the internal calculation accuracy of REW :
The Neumann measurement show large variations in low frequencies because the microphone was in an acoustic null of the front bass reflex port, I think, and what we see below 60 Hz is noise, while the back port of the JBL provided some useful signal since 30 Hz where the microphone was located.
EDIT : Each speaker was positioned at the same place within 5 mm. I didn't evaluate the error caused by small variations in the position of the speakers within these 5mm.
EDIT 2 : the 4 curves above are for the JBL 305p, always the same speaker vs the other.
