If you compare Amirs measurement of the Neumann 310 you will see the dip is missing and also above 5 khz the level is a bit lower. I tend to believe the further you measure more deviation there will be.
A bit off-topic perhaps, but please note that S&R KH310 measurement is also at 2m (the same distance that NFS calculates CEA2034 data for), so measurement distance shouldn't be the cause of the (very small) deviations between the two.
Here is the digitized S&R measurement overlaid with the ASR one:
The bass dip in ASR measurement is only -1,5dB vs S&R and the HF difference above 10kHz is at most <2dB. The rest matches very nicely (except the much higher resolution of the NFS measurement). Note that this is actually within
manufacturer specified unit-to-unit tolerance of ±0.87dB (100Hz to 10kHz).
The bass dip in ASR measurement may also be explained by the relatively cold temperature when doing the scan, from the review:
Temperature was 58 degrees F initially. Past experience indicates that there may be some impact on bass response of Neumann speakers so a second measurement was performed after heating up the room to 68 degrees (it dropped back to 64 at the end of testing).
Note the temperature dependence of LF performance is explained in
KH80 measurement #3:
Suspicion quickly went after the temperature difference for when I tested mine (in winter) and theirs (temperature controlled at 21 degrees C). Guy showed me a couple of useful slides from Klippel indicating changes in speaker parameters based on temperature:
And:
So Guy put a unit in the fridge overnight and then made measurements in the morning every 3 minutes as the speaker and its components warmed up. Here are his results, normalized to 21 degree C (black line):
As we see in the bottom blue line, lower temp most definitely created the dip around 80 Hz and gradually disappeared as the speaker warmed up.
Since we're talking only ~1,5dB difference, several degrees in temperature difference might cover it. Another explanation could be related to the splicing/calibration method employed in the S&R measurement - but I'd personally bet on the temperature.
For the HF difference I can think of three very likely reasons for the deviation - different microphone calibrations, tweeter unit tolerances and/or differences in air absorption coefficient (due to e.g. different temperature, humidity...).
In short, it is IMHO very unlikely that S&R measurements would be invalid due to them sometimes measuring from further away, since they seem to be doing so in anechoic conditions. In my opinion the two KH310 measurements match really well to one another in all of the important ways - and actually nicely showcase how comparable results can be even when obtained by very different methods.