Volti v Charney v Rethm

... my concern would be bass energy in a large room because of cancellation of the front and back output which are out of phase (this reduces bass by 6 db/octave).

I believe this is true in general,  but as per Ze'ev, not so much with his PAPs as his drivers?/implementation? reduces this typical OB cancelation (exactly how I do not recall). Unless Larryi has measured this cancelation himself or knows a reliable study showing this for the PAPs specifically,  I would ask Ze'ev directly if this is a concern. 

I was impressed with the bass of both the Quintet and Trio speakers I heard because I like fast and nimble woofers that can keep up with the kinds of midrange/treble drivers they use which are also very fast and dynamic sounding.  I also saw that PAP employs the kind of woofers I like which use pleated paper surrounds—those tend to deliver very clean and articulate bass—but because they also limit excursion, they don’t deliver deep bass at high volume levels.  I admit that I don’t prioritize extremely deep bass, so I did not evaluate the PAP speakers I heard for that aspect of performance.  My “concern” was hypothetical and raised as something to look into rather than something I actually heard.

I did see that PAP did employ one approach to reducing back wave cancellation—they effectively widened the baffle with small side supports that extend backwards like the side of a conventional speaker with no back.  This is commonly done with open baffle designs.  It is generally considered better to “widen” the baffle with such wings than to use a wide front panel because of problems with reflections off a wide baffle and diffraction issues.

Aside from the particular demands here--large room and high ceilings—my favorite speakers mentioned here are the Charney Companions with AER drivers and the Quintets.  If corner placement works, I would add the fieldcoil version of the Audio Note AN-E to my personal favorite list.

@larryi - Thanks for your informative post.