Woofer sucking in and out

When i had my old setup, the woofer pumping was mostly due to acoustic feedback via the floor. The speakers shook my suspended wook floor which shook the table and generated very low frequency output at the cartridge. Playing these inaubdilbe low frequencies suckup lots of power from the amps and displace the woofer cones outside of the linear operation zone. Distortion is generated at the amp level and at the speaker level. Bass is indistinct and spatial clues became weird probably from from increased THD + phase distortion. In addition, the wild woofers may generate a reactive load for the amps.

I got a minus K isolation and put this problem to rest.

The contribution from record warp is solved with a record weight along with a ring. However, acousic feedback is the key issue which magnifies warp problems.

Without properly addressing acoustic feedback, the record warp generate low freq signal from the cart - > speakers ->floor -> table -> cart -> speakers -> etc. The dance of the woofers is a result of positive feedback loop.

Subsonic filters will break this loop too. Betw the woofer dancing and phase shift with the filter, I take the filter anyday; but not all filters are the same though.

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.