How can you not salivate over the Shiva 12. I've been trying to find a site I saw some time ago on this sub that was built into the floor. I think it was an Italian audio site that showed like 24 12" subs set in a "horn" made out of stone or concrete that ran under the guy’s listening room. Pretty spectacular looking.

I think one of your earlier posts said something to the effect that sonotube-type subs were mostly for HT. Are you familiar with Hsu subs. Very similar to sonotube construction, but from everything I've read are considered "audiophile" grade, that is accurate and very musical.

Finding the center of a circle can be done by several methods:
1) Center of mass. Assuming perfectly round and uniform density, the point at which it balances is the center.
2) Also, the longest cord (a line that connects two points on a circle's circumference) passes through the center. Simply measure the longest distance across the circle and mark a line. Do this several times around the circle and the intersection of the lines should be the center (or pretty close).....Colin