Riker,
Do these company's selling the "tube" design bass trap have any testing proof of their performance? It has been proven that the bass trap should "straddle" the corner for the best performance. This can only be done in in a rectangle shape.
I am not sure on the benefits of the round tube, before you build any or buy any, I would suggest going
here and asking Ethan and the other experts if such a design works.
I am assuming that he will say that it will not provide as a substantial improvement as the straddling bass trap designs would. The reason the straddling is optimum is because it leaves an air gap behind the trap which aids in further absorbtion.
Just a word of caution, there are alot of phony acoustic products on the web!
