Also this site provides some good lessons and a weekly newsletter that pumps out some good information. They obviously show a bias to tube traps. ASC Hifi - High End Listening Rooms
Yup. I’m somewhat of an ASC TubeTraps fan myself as the pics suggest. In fact it was the paradigm shifting experience of first hearing an Art Noxon designed listening room treated by Tube Traps back in the mid 1980’s which inspired my life long interest in small room acoustics and acoustic treatments. By the way, each Tube Trap sports an aforementioned poly-cylindrical diffuser running down one side of the cylinder.