OK, here are the 288 plots redone. 50dB scale, 1/6th octave smoothing.
Please not that driver #2 was measured off axis. Also see below driver #1 which appears to have a better response. It was not measured off axis.

On the driver #2 plot you will also see the H2 distortion. It rises below about 700Hz. This is true for both drivers, tho not shown. H3 is similar and on both drivers.
288 511E 50dB
288 D1