I also have an 18" Velodyne subwoofer. The cone excursion is servo controlled in a real feedback loop, right where it matters. The Velodyne blends in superbly so I only become aware of it when particularly low notes play!
@jsalemo277
Speakers like the KEF Reference series produce huge volumes for their size, in part because they use aluminium for the voice coils. Aluminium is 4 times more conductive than copper, weight for weight.
I am convinced that to get a great soundstage, you cannot go past apparent single point speakers, like KEF, Fyne, later Quad electrostatics, Tannoy ...