Ask and ye shall receive.
Measured 1W 1M SPL is blue, modeled is red.
We measured outdoors over a driveway, so this was not a perfect 2pi measurement by any means. Ambient noise was ~50 dB, so >25 dB down from the measurement levels. This measurement is certainly adequate to verify the performance of the design. We are essentially flat (+/- 3 dB) from 25 Hz to 100 Hz. 2.83 V yields about 86 dB at 1M, which is very close to the prediction.
Drive voltage from amplifier was set at 2.83V into an 8-ohm resistor with my most accurate voltmeter. My equipment is probably accurate to a dB, and should be flat within the area I have presented. Measurements were made with REW using the equipment I have described elsewhere.
I also did a little experiment with HolmImpulse.
Measured SPL and THD:
Hmmm, it is a 25 Hz tapped horn design and the THD takes over below that, pretty much as I expected, and exactly as theory predicts. I did not bother with the higher harmonics - they were buried in the noise.