It's been on/off for about a year. I thought it's because I have a few items on top of the sub, so I'd occasionally re-arrange them. Finally found a scene that consistently produces it and kept replaying it see what/where it's coming from.
Definitely from the back of the sub, seems like it's inside. Seems to only happen on low frequency scenes. It's a metallic rattle/vibration
VTF-15H MK2
Volume set around 10 oclock
Q = 0.5
Both ports open
EQ = 2 (tried closing off 1 or both ports, and changing EQ, no big difference in the rattle)
Crossover = out (but when I switch it to in, and change the cutoff to the lowest (30 hz, I think?) the rattle is still there, but less)
Listening at about -30db to -25db post AVR calibration (not loud)
I have a video:
https://drive.google.com/file/d/1lQO...ew?usp=sharing