HELP-woofer moves alot when playing lps

And what system would that be, Inna? If you call listening to records "experimenting," no wonder we intrigue you.

Isn't analog playback fun? The old adage, "Ignorance is bliss." holds true. Just like an onion, we peel back the layers just to find more layers. Cartridge alignment, cartridge tracking, VTF, VTA, suspended turntables, rigid turntables, high mass, low mass, wood floors, concrete floors, ported speakers, unported speakers, wiring, tubes, on and on. No wonder so many young people walk around with mp3 players plugged into their heads!
I love this hobby! I really do. As frustrating as it is when things go wrong, it is just as rewarding when finding a solution. It is like we each become an active participant in the music. So many good solutions to overcome the typical problems. And Audiogon provides us with a great support group when we hit a wall. There, I just wanted to say that.
I think everyone is right regarding what has been said on this page. All the different types of turntables, speakers, and electronics in-between lead to many different solutions. I experienced the woofer issue years ago too. I could even induce feedback in my system by cranking the volume. That lead me down the path of isolation and to my current turntable which I think, like many great turntables out there, provides a firm foundation for the spinning record.
I have also experienced the occasional record with built-in rumble that excites the woofers. Mostly, I do not have much of an issue because I simply do not play music at ear splitting levels like I did in the 70s and 80s. But for those that do- then solutions like a low pass filter are perfectly reasonable. For some of us purists, the idea of a filter risks missing out on some of the music. For example, an organist who uses the 16ft pedal to give his music a certain character. Or how about the cannon fire on Terlarc's pressing of the 1812 Overture. There's a test for your cartridge/tonearm. The grooves in the record make nearly a right angle turn! So hopefully, the low pass filter is needed only for those certain records with high rumble. I remember years ago playing one of my favorites, Dark Side of the Moon, cranked way up. The woofers were excited as soon as the needle was dropped into the grooves, but the most fun was watching them pump out the heartbeat. Bragging rights to those whose speakers could blow out a match. :) Of course, I'm much too mature for that now.

I had this same issue in my system....tore my hair out until someone suggested that it is some kind of RF...from airport, etc. I replaced my cables with shielded ones, and the pumping was gone. ...I'm not saying that is YOUR problem, but it was mine. ..by the way, you CAN change the mismatch of cartridge/arm by adding weight to the cartridge end of the arm.

No, that's not that, I do listen to records but don't have such damn thing.

Just got a KAB filter and installed it. Much better!!!

One thing that is for certein is that many records are often not flat, but have minor warps that cause this great displacement of the woofers due to the low frequency. It's not the problem of the table, the cart, ot the isoltaion. It IS the record and the ONLY way to solve this is to use a low pass filter. It is down 3 dB at 18 Hz and continues down at a steep 18 dB per octave from there. This is not going to cause any negative effects. And bass is in mono anyway from 140 Hz on down and the filter also removes any vertical rumble in this region.

The KAB has in fact has tightened up the bass in my system. Highly recommended!