Returning to my original posit (and hopefully someone within JBL can reply) it seems prima facie odd that a doubling of the the components results in a reduced a sensitivity rating, OR, what are the in-house sensitivity rating protocol differences that produce this result?
There seems to be a discrepancy of about 1.5 dB from the STX 835 spec sheet's 96 dB "passive mode" sensitivity compared to the FR chart, which looks to be more like 97.5 dB in free field.
Since the cabinet is designed to be flown, it shows measurement in both free field and half space.
The half space measurement shows 100 dB sensitivity at 50 Hz, rising to 104 dB at 70 Hz.
Using the 2226 spec sheet, we can interpolate from the 60 watt chart that the "0" line on the frequency response curve of a 5 cubic foot vented cabinet is 97 dB 1 watt one meter half space, about 96 dB at 50 Hz.
The STX 835 (probably about 4 cubic foot net per driver) is as much as 8 dB more sensitive than the 5 foot vented cabinet, but rolls off at about 12 dB per octave from 70 Hz, at 40 Hz the two boxes are about the same sensitivity.
Classic illustration of Hoffmann's Iron Law, low, loud, or small-pick two.
Also an illustration that using a single sensitivity figure is useless, you need to look at the FR graph to determine where the sensitivity is derived.
Anyway, thanks for the links, this is the first time I ever saw JBL underate (even if only by 1.5 dB) sensitivity on one of their cabinets.