Important bits printed (mounts not even designed).  Having fun ramming fluff into the transmission lines to dampen them.  Certainly more art than science.  Fortunately, REW, a calibrated microphone and lots of faff are bringing back the science part (iterate and save all the frequency responses).  Will report more fully soon.

in the mean time:

• REW - Room EQ Wizard (Get it, download it, enjoy it.  All sorts of awesome if you like audio - and it's free):
  • https://www.roomeqwizard.com/
• MiniDSP calibrated measurement microphone (does cost money, but... well, I wanted one):
  • https://www.minidsp.com/products/acoustic-measurement/umik-1