I posted this in the subwoofer forum but didn't get much traction. The sub is a commercial one but the mods are DIY. I had always heard to put fill in a sealed sub, but for a ported one, not so much.
https://www.avsforum.com/threads/re...&share_fid=47413&share_type=t&link_source=app
Results from adding poly fill batting to a ported sub
www.avsforum.com
https://www.avsforum.com/threads/re...&share_fid=47413&share_type=t&link_source=app
Results from adding poly fill batting to a ported sub

Results from adding poly fill batting to a ported sub
Playing around with REW, a MiniDSP and demoing different source material has revealed limitations of my sub, a Klipsch RW-12D. Pushing EQ boost below the port tune plus aggressive audio (Cloverfield Paradox e.g.) resulted in chuffing and high harmonic percentages, among other things. So before I...