My 12 x 24 room with cathedral ceilings poses some acoustic challenges. As you have always said, the more traps I add, the better the sound. I have about 12 in the room, but the corners aren't covered very well.
So I was going to build some DIY tube traps, then I saw your comment "most of the DIYs I've seen are a joke...." So I ask: Why?
I was planning to make them a minimum of 16" in circumference.
Is 2" thick fiberglass pipe insulation better than 1" or is there some disadvantage to using 2"?
Just for fun I googled tube traps VS... and google filled in "real traps" so I checked a few of the threads. If you still want to build tube traps after checking out these discussions, maybe there is someone here who can help point you in the right direction.
If you haven't, ask yourself why you're considering a resonant absorber. More than likely, it's because you have some kind of peak or decay issue in the first three octaves. Should that be the case, know that there is no specification of which I'm aware that says you need a particular decay time for that range. In the spirit of self-promotion, here's a video I made recently which talks about this. Ethan, of course, had a phenomenal one up which included balloons and more detail but I can't find it.