Hi Ozzy,
can you share a little more about your DIY HFT Bell tweak.
I take it you got some 1/4" copper caps but what did you use to put inside.
I was at a guys place and experienced what initial looked like bare room, no room acoustic panels or even plants noticeable but actually had HFT's + the FEQ - most defiantly transformed the space. Was nice enough to remove and go through the process, I was kinda shocked with the difference and now intrigued with what you wrote.