Subwoofer rumble issue

This filter you bought, is for very low arm cartridge 7-12hz resonance (below 20hz), this you can’t feel or hear, it’s just very slow woofer movement.
I think from what you described you problem is far higher, around 30-70hz this you feel and hear like an ever increasing earthquake.

If you have floor standers with half decent low bass as your main speakers, try doing the "donk" test again but with the subwoofer/s turned off this time. try it even if they are just stand mounts also.

Cheers George

+1 georgehifi
A subsonic filter will not solve the problem! The table is what you should address!
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=47974

And what’s causing the problem with the table? The subwoofer. The REL is driving the room. It’s the structureborne vibration, seismic plus Rel. The resonant frequencies Fr of the cartridge and tonearm are circa 8-12 Hz, the platter can be even higher. Some rooms are incredibly microphonic, especially the upper floors of buildings. Some racks/stands amplify the vibration. The REL weighs only 42 lb so my cryo’d Baby Prometheans would be sufficient to properly isolate the REL. $48 free shipping, cannot beat with stick!

Just out of curiosity, try inverting the phase on the subwoofer and see if it makes a difference. 

@kalali yep tried that. Nearly took the whole building down. Yikes!