Back in the day when I was more into tinkering, Google (and Yahoo & Alta Vista... I'm showing my age) was a good source for technical papers. Now it's all geared to sell stuff and I can't find anything to refresh my knowledge of T-line theory.
My recollection tho was that USEFUL sound emerged from the end of the line. I've read that it's important that the line be damped, but never read that the goal is to absorb & kill that backwave.
Not to appear to be a Shahinian fanboy but wasn't the Contrabombarde a true TL that was flat to 16hz?
I saw & heard one once at CES and it was large-- but no bigger than a 70s console stereo.