I suggest getting rid of the problem rather then covering it up with a filter. Linns do best on very lightweight small tables ( probably the Dual too). The next thing to think about is the cartridge/arm compatibility..you don't mention the arm or cart. A major mismatch here would actually make the cartridge mistrack you don't mention that. These large subsonic excursions are caused by waves...many times the front of your supporting table will move differently than the back. If your table that supports the turntables are close to the wall, either anchor the table to the wall, or put a prop between the table and the wall to prevent the table from moving inappropriately....I would try these things first before clamping down your system with a filter.
Low frequency problem while playing vinyl
Has anyone experienced (and knows a cure for) a very low frequency problem while playing records. Just recently I hooked up two old turn tables, Linn LP12 (1980s) and Dual 704 (1980) in my system and the woofers of my speakers are almost jumping out of the speaker cabinets while I am listening to a record. Displacement at least 0.5 inch if not more and the keep "pumping". Needless to say that I didn't experience this issue years ago when I used to play records regularly.
amps: Krell Ev202/350MCx
speakers: Thiel CS7 + smart sub
phono amp: Valvet
amps: Krell Ev202/350MCx
speakers: Thiel CS7 + smart sub
phono amp: Valvet