There is no substitute for cubic inch or in this case surface area

@dynamiclinearity Thank you for pointing out Q = 0.707 (1/√2) resulting in flattest freq. response. Do you happen to know how is it derived? 

@asvjerry 

24" =  452.4 sq in.

nah nah nah nah nah!

Hartleys kickin' butt.......

And BTW you can't see them move and will play subsonic.

"Just doin' a little Hartley hammerin'....." *L*
Keeps the skin supple....try that excuse on the sig other... ;)) 

Let me know if it works at all....😎

We had a 32" Clarion sub in our possession for quite a while.  In a 6 cu ft sealed enclosure it would rattle the rafters in our (and adjacent) building -- while moving about 1/4". 

Thoughts on the OPs observations:

What might be happening here an aggregate of amplitude, detail, and dispersion. While smaller drivers are very good at projecting an image from wall to wall, they may be a couple of dbs short of a glorious presentation.  And, have to work pretty hard when dynamic passages demand that the drivers to move large distances. When you have large bass drivers of dipping well into the subsonic region and producing massive amounts of bass, the speaker designer can "open up" the other drivers (or choose higher efficiency drivers) and let them play, thus increasing the dynamic range of the entire musical bandwidth, and lower overall distortion.

At lower levels, the system is just humming along with low distortion and plenty of dynamic headroom on reserve.  This lower distortion also keeps spacial cues intact, thus providing a coherent soundstage, while maintaining detail and focus.  In this way, the speaker with more "cubic inches" may, in fact, provide a more realistic presentation than a smaller example.