What Do You Think . . . and How Does It Work?

Kenjit, I’d say millercarbon is correct and the effects of pressure on the inner walls of a tube (incidentally, specifically engineered to uniformly hold pressure) is a great idea. Cabinet resonance would be low using this material and geometry, especially if you used schedule 80. Talk about inexpensive DIY!

If designing a tube shaped cabinet, it would be logical to use at least an inch or two larger radius (inner dimension of the tube) than the ports on the driver basket to allow the driver to breathe correctly, with a beveled edge on the baffle to allow unrestricted airflow from the back pressure of the driver.

The bazooka style used in car audio worked well.

Kenjit, explain to me why it wouldn’t work??
(Oh and I don’t specifically think it’s not the material so much as the geometry of a tube that makes it such a good idea).

Kenjit, um... concrete pipe?
And yeah, certainly competitive with other devices claimed as state of the art. A cabinet's audible colouration (coloration) has a significant signature to the overall sound, a tube will do well in such a situation as the tube itself lends to withstand pressure from the driver.

Let's face facts though, best engineered for sound quality, isn't necessarily aesthetically the most pleasant.