Why do my bass drivers shake violently listening to vinyl

Hi all, OP just checking back in. The KAB rumble filter resolved the issue. It would be nice to establish root cause, but for now I'm happy. Speaking of compliance, does anyone know if there would be a compliance issue with my AT VM760SLC mounted on the stock Technics SL1200GR arm? I also may consider purchasing the after market footers KAB sells on their site. Thanks for all the great discussion and happy holidays to all. -Joe

It sounds incredible! I'm just concerned that I may be doing damage to my speakers. 

@sbank No. None of that is happening. And this isn't the first time I've seen this. It happened with a completely different set of speakers and different cart, on the same table. I thought it was something particular to those other speakers. 

@erik_squires Excellent post!! 

I suspected it was dangerous. The excursion or cone travel is pretty extreme and it seems to be as you said with no spring holding back the driver. 

And, yes, I have a springy wooden floor in a second floor bedroom and a cheap Pangea audio rack.

I could try plugging the port although with the Treo's they are located on the bottom. I will absolutely look into getting a rumble filter.

Thanks all!!

@williewonka how can I tell if the bearings have any play in them? Not sure what you're referring to.

@artemus_5 I noticed this any time any record is playing. It is not genre specific. And like I said, there is no discernible audio issue. Just the bass drivers going in and out like mad. 

Thanks @stereo5 I think that is the route I will go down. For my own understanding, is this a turntable feedback loop? The low frequencies being put out by the speaker are traveling along the floor, into the rack, picked up and amplified by the cartridge and phono pre and sent back out the speakers further exacerbating the issue?

I really appreciate everyone's responses. This has been a big help....

@williewonka interesting thread before it went off topic. The KAB rumble filter was brought up. Here is an excerpt from their site which accurately describes what I am seeing:

Getting into LP's and startled at the big speaker cone movements that you're seeing? Thinking a better turntable will help? It may not! This very low frequency energy is called rumble. Much of it is actually cut into the record groove when the master disc was made. But the main source is feedback exciting the natural stylus/arm resonance between 7 and 12 hz. This produces a slow easily visible in and out motion of your woofers. If you cannot see this motion, the RF-1 will not solve your feedback problem. If you can see this motion, the RF-1 will solve your feedback problem.

• Do the woofers visibly pulse in and out i.e. you can see the movement - Yes
• Is the "shaking" consistent for every album - Yes
• are the albums warped, so the pulsing matches the album warps - No
• is the platter free from warps - Yes
• is the bearing in good shape - Brand new Technics 1210GR
• is the stylus clean and in good condition - Yes brand new AT VM760SLC
• what kind of stylus are you using
• does your phono stage have a sub-sonic filter - Not sure. It is a Herron VTPH-1. I'll have to research that.

@melm It seems my cart is a very popular choice according to the Technics SL1200 FAcebook group. Many users using this cart.

"Working" from home today so I moved the TT from within the dormer area on the Pangea shelf to outside of the dormer on a much more stable IKEA Kallax shelf. (see Audionoobie's system pics) Was pic 4, now is pic 3. 

Same problem....

Seems like I'll be looking for a rumble filter.

@yogiboy Technics SL1210GR arm and AT VM760SLC cart. 

Arm = 12 g
Cart = 8 g
Fastener Mass = .5 g (guessed)
Compliance = 10 x 10-6 cm/Dyne  

Tonearm Resonant Frequency = 11.12 Hz

I purchased the KAB rumble filter. As soon as it comes in I will post my findings. Thanks all for the enlightening discussion. 

@limomangus I haven't been listening to my vinyl rig since I discovered the issue. Streaming only.