Earlier on I mentioned the problem with using a free field calibrated measurement mic within a near field setup.
And this is the red herring. Because of the close range at exact tweeter axis on axis you will get a rise in the high frequencies ( source:Beyer Dynamic):
Some food for thought:
The spinorama is based on generated reflections in a room and are based on anechoic measurements. But a room is not all about reflections. Below the Schroeder frequency the standing waves take over:
How predictive are the...