The evidence available strongly indicates which measurements are most likely to be incorrect.
Already in January
@napilopez had
posted the following comparison (Klippel means ASR measurement)
View attachment 68193
This already indicated that something could be wrong with the ASR measurement.
Then Amir took a second sample. The second measurement also shows the strange behaviour above 4-5kHz and below 100Hz.
Not sure if the measurement conditions were identical (fitting error, resolution,...).
The second one measured pretty much the same:
View attachment 68195
If we are generous, the deviation of the two samples is +-0.5dB in the range 60-11000Hz:
View attachment 68196
This means that the first sample also worked correctly.
Now we also have the new measurements from Neumann and the confirmation of the measurement by Klippel himself.
As already mentioned, the deviations of the ASR measurements in the upper frequency range were due to Amir making measurements with the mic protection cage. Only the low frequency behavior is still a mystery.
If that were all, I would agree with Amir and others in their doubts that the measurement by Neumann and Klippel could be a "golden sample" that was corrected in the bass range.
I have smoothed the frequency responses a little bit to be able to see the deviations better.
View attachment 68197
But in the meantime we have so many ASR measurements that differ significantly in the low bass frequency range from the manufacturer's specifications or measurements in audio magazines that it makes it very likely that the problem lies with the ASR NFS.
To confirm this, we actually do not need the Neumann sample anymore.
Apart from that, the ASR measurements up to 10-12kHz now correspond very well with other measurements.