I can't really salivate over a speaker sonstruction that
can double as a load-bearing support for a house. :-)

Just too much.

But the Sonotube construct intrigues me and Bill Fitzmaurice
made mention that some sub drivers were on deal at MCM.

The Shiva costs about $130. Does Eminence or any of the
others in the 8" to maybe 10" range meet the requirements
of a sonotube? They show 2 drivers and a longish port on the
interior. And where do you put your plate amp?

I think the sonotube can be built with off the shelf
parts from Home Depot including the circular top and bottom.

A groove would have to be cut in pre-made small size
'table tops' they have to accept the tube. A 4" hole saw
can make the port cutout for either carpet roll core or
PVC.

My high school geometry tells me you need the radius
of a circle to find the center. Are there any methods I missed
which can calculate the center w/out a radius?

Alternately, here's a kit I posted some months ago from
CSS:

• Sonotube kit