Woofer sucking in and out


I have a problem with my analogue set up that once it starts play, the woofers of my speaker will move in and out like crazy, unrelated to the music! It relates with volume as when the volume is low, the woofers will not move as much. May it has to do with oscillation between cartridge and arm but my set up is new. The turntable is Acoustic Solid-Transparent and rega301 arm with cardas wiring and weight mods, Herron VTSP 3A pre and VTPH phono. I wonder if placement has anything to do with it or power connection.
I hope someone who has the same problem before can give me some hints.
Thanks.
luna
Tuning the resonant freq of cart/arm can damp some vibrations or at least reduce the excitability. It is part of the feedback loop. If the floor vibrates at higher frequency than the reson freq of the cart/arm, it will provide damping. If the floor freq is the same as the arm/cart reson frequency, the effect is amplified. If the floor freq is lower, the carm/cart tuning will not provide adequate damping. See Minus K article on transmissibility of vibration.

Some speakers have output below 20Hz. More so, while the floor will damp a lot of the higher audible frequencies, it may end up moving at a lower frequencies after being excited. Many of us feels the floor vibrates at heavy bass passages but we don't hear the floor playing bass.