Why the woofer moves badly when playing certain LPs

Hi Starbusters, many lacquers are now cut on old poorly maintained lathes. They can produce prodigious amounts of rumble coming from both the main bearing and the worm drive of the cutter head. This will cause your woofers to bounce around and even bottom out. With most speakers the rumble is so low down you won't hear it and if you have grill cloth on your speakers you might not even notice it. In my case having four large subwoofers the whole house shakes. I have already sent three records back this year alone due to this problem. It can be made worse by poor tonearm/cartridge matching but I do not think that is your problem. At best this robs you of power and Doppler distorts everything else the woofer carries. At worse it makes you whole house shake. When you get a record like that send it back and complain. Unfortunately, most people do not recognize this problem so do not complain. 

Ralph you need to come to my house and I will demonstrate. Most of the bad records are coming from the likes of Warner. The lathe is the only mechanical step in the process now. So it is the lathe by default. When I first got one of these records I thought my turntable was shot. I put another record on, quiet as a mouse. Since then I must have returned at least 20 records for this problem. I may be a bit more sensitive to it because my bass goes ruler flat down to 18 Hz then rolls off at 80 dB/Oct (digital filter). You will notice that Starbusters only notices this with NEW records. Not old ones. It therefore could not be a cartridge tonearm miss match. Until about 10 years ago I had never had this problem. So I am waiting for anyone else to give me a more logical explanation. 

Ralph the 18Hz is as measured. I use room control.

Other than both Starbusters and myself being head cases. Geoffkait, keep your mouth shut.

Absolutely mc. Mostly with small warps and surface irregularities. Not all new records are bad. Some are terrific and there are several companies that consistently put out great product. I can't remember having trouble with built in rumble in the past but I certainly had a lot of trouble with noisy pressings particularly with popular music. Classical pressings were always much better. Rock was hit or miss. I have some old DECCA records that are astonishing. 

Your woofer is playing the warps and surface irregularities. All that is certainly less than 10 Hz. That arm does not look all that heavy and I would think the AT would do fine in it. If you want to know for sure you have to get a Hi Fi News test record which has both vertical and lateral resonance bands and you will be able to determine exactly where your resonance frequencies are. If they are below 8 Hz you have a miss match and Ralph is correct. It could still be rumble from the lathe in which case your resonance frequency will be above 8 Hz and it would be the only possible explanation. But if it were rumble I would think you would also hear something as there are components in rumble above 18 Hz as the rumble I am talking about in certain records is more than audible and I also never turn my filter off. There is certainly a fault in those records as you say many do not do this. If you do not have a miss match the only solutions would be get a subsonic filter or don't play those records.
I use a digital brick wall filter at 18 Hz as I have an 8000 watt subwoofer system and at the volumes I frequently listen at I would probably launch woofer cones across the room. Actually what happens is the voice coils hit their end stop and make a very disconcerting bang. Without the filter you can't hear anything down there the house just shakes and you waste a ton of power until the voice coils bottom out. IMHO anyone who listens to vinyl and has a subwoofer system needs a subsonic filter. Even if they have a properly set up tonearm. Unfortunately in the analog world this is impossible to do effectively  without attenuating the bass or causing sonic degradation. But in the digital world it is no problem. What ever degradation is caused by digitizing your phone amp is more than made up for by digital bass management and room control. 

Cleeds, have you actually impulse tested your system and looked at the frequency response curve? Are you using digital room control? Being meticulous with setup is very important and it will certainly help but even if you have your tonearm set at say 12 Hz there is still going to be plenty of rubbish below 10 Hz that is going to get through. With the volume high enough everybody's woofers are going to flap at least a little unless they have a filter and in analog it would have to start rolling off at about 30 Hz.
It is true that sealed systems will flap less than ported ones because pressure does not build up within the enclosure. 
This may well not be a case of rumble in the record as I previously thought but there is certainly an element of record quality here and speaking from personal experience there are many modern pressings with rumble built in. 

Cleeds, since when is a resonance point a "brick wall" situation. The resonance peaks then rolls off. If your woofers do not move at all visibly and you are playing vinyl either your woofers do not go down very low or your cartridge is too stiff for your tonearm and your bass is rolling off prematurely. I suppose you could also be listening at the volume of a mouse squeak. I would never use an analog filter. It would damage the bass too much but digital is a whole other world. I could survive without it but volumes with certain records would have to be limited and It might rob enough power to affect the room control function. There are no downsides to a digital filter up to 80 dB/oct. With a 3 dB down point at 18 Hz the effect is totally inaudible. 
The problem Cleeds is that the source is vinyl, a medium that is imperfect at best. So, treating it at it's source means not playing records.

I am not a big fan of periphery clamps. It is a lot of extra weight on your platter's bearing and they are a PITA to use. Vacuum or reflex clamping are better solutions. Vacuum will remove some of what we are seeing but not all of it. Starbusters, get one of these  https://www.musicdirect.com/analog-accessories/hifi-news-test-lp-producers-cut
and tell us what your resonance frequencies are. This could be a great learning experience. If there is a miss match here it will be fun to see how correcting it changes your woofer flap. 

Ish_mail, I shall assume you have an SME. Great table. Great clamp.
I am not sure what it would take to bottom out a Clearaudio bearing but they do make a peripheral clamp for their tables so I would assume that it works OK. I do not think I can tell much difference between reflex clamping and vacuum (I have both). Certainly, the vacuum method subjects the record to less stress but I have never seen a record cracked by reflex clamping. The SOTA vacuum system is brilliant but admittedly more complicated than a reflex clamp. The Michell reflex clamp will work with just about any turntable playing 130 gm or less records But when it comes to 150 grams and up you have to push down so hard on the bearing to flex the record into the platter you might eventually damage the bearing. The threaded version you have is brilliant, just hold the platter and tighten it down. 

Cleeds, what your equipment is speced at has nothing to do with your system's bass performance. Judging by your opinion you do not have any bass. Impulse test your system. I'll bet there is nothing below 40 Hz.