I don't.
I can't even see any tolerances (+/- dB) specs on their website, let alone graphs of any kind, including a simple on-axis, let alone off axis, let alone 180 (behind the speaker). Lacking on a lot of technical detail and no clarification on sensitivity spec (1W or 2.83V)
Just dipole woofers stitched to monopole tweeter this is not state of the art dipole design like Sigfried Linkwitz or John Krevskovsky at all, and nowhere near the a Jamo R909 which clearly is the prototypical speaker of this class...