A search on "woofer pumping" shows 22 threads.
Tbromgard
I recommended spending some time isolating your TT, Gear and speakers better so they are not affected by structure feedback. The speakers can in fact be aimed at your TT - sound pressure (acoustic feedback) itself is not the problem. When the acoustic feedback is absorbed by the rack, shelves, floor and walls around your TT, gear and speakers and changes to structure feedback - this then becomes the problem - if your TT, Speakers, gear are not isolated properly. See also the last 30 or so posts on Copernican.
IMO - Any filter not recommended by the speaker manufacturer themselves should be considered a 2nd option only after isolation attempts fail. Its a band aid, another layer.
Good luck.
Tbromgard
I recommended spending some time isolating your TT, Gear and speakers better so they are not affected by structure feedback. The speakers can in fact be aimed at your TT - sound pressure (acoustic feedback) itself is not the problem. When the acoustic feedback is absorbed by the rack, shelves, floor and walls around your TT, gear and speakers and changes to structure feedback - this then becomes the problem - if your TT, Speakers, gear are not isolated properly. See also the last 30 or so posts on Copernican.
IMO - Any filter not recommended by the speaker manufacturer themselves should be considered a 2nd option only after isolation attempts fail. Its a band aid, another layer.
Good luck.