Metallic rattle from back of VTF-15H MK2 sub

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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

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Clarification: it's less of a rattle more of a high speed ticking sound. When I run the test tones CD, it's audible in all the frequency ranges (I just don't notice it normally since the other speakers are on), but more prominent on #11 - 25Hz

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I've narrowed down the issue! If I press down on the outside of the Q-control knob, the rattle/metalic vibration fully stops. How do I fix it?

(pressing any other knob doesn't help)

[Kevin_Hsu]

Hi there,

Sorry to hear that. Try pulling off the knob and tighten the nut around the threading on the potentiometer with a small wrench or pliers. Play that same material and see if it rattles.

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Alright, that was easier than I thought... the washer on the back of the Q-control knob was rattling against the enclosure. Tightened the nut, and all gone. Thanks Kevin!

[Kevin_Hsu]

Glad to hear it bud!