Yeah baby....I found a mate

I'd disagree, as does the Tannoy distributor i've dealt with-DMT 12s fill up a room nicely-nicely sized footprint and more than enough bass. 15s are nice but the bigger drivers also mean slower response and greater overhang.

Give me a break, Slower response?...I would figure that an educated speaker guy from Tannoy would be ahead of such "folklore"...or is it the speaker fairies?

Yes genius, that's right. Free advice from someone who knows as well as a Tannoy dealer who knows better than you. Very doubtful that more bass than the 12s throw out's necessary unless you're reliving your teen metal phase, but if more's needed just throw in a sub.

Actually Tannoy and other companies should have followed the B&W example and used multiple moderate-sized drivers on their larger speakers rather than a single or double 15", precisely so as to avoid this.

B & W noticed the same laws of physics that you didn't pick up on and went with smaller drivers.

Are you sure B & W didn't go with multiple smaller drivers to avoid massive cabinets? Compare the cabinets of the 801 Matrix and Nautilus iterations.