Sub Sonics and woofer pumping

I had a similar issue with my Kuzma Stabi R turntable that was on a HRS platform sitting on an audio rack.  I was getting acoustic feedback resonance between the audio rack and the turntable causing the woofers to pump heavily as soon as the needle hit the record. I had to further isolate my turntable by replacing the regular feet on my HRS platform with low frequency absorbing feet. I suspect that your turntable needs similar isolation.    

Its probably the rack. Different approaches can be taken. Here's mine:https://systems.audiogon.com/systems/8367
A good relatively simple way to see if this is indeed the problem is to set your turntable up on the floor. The best rack is no rack and the floor is pretty hard to beat. If the floor is indeed better then we know its the rack. The next step is either a better rack, or use something like a shelf with mass like sand, or springs, or something to help reduce rack vibrations from reaching the turntable.

Yeah. Maybe. The thing is sound isn’t up loud enough to cause vibration In the turntable. 

Are you saying the operation of the TT is causing the pumping?

Here's a good explanation -

https://www.audioadvice.com/videos-reviews/why-does-my-turntable-make-a-loud-feedback-sound-when-i-turn-up-the-volume/#:~:text=The%20cantilever%20on%20the%20end,what%20creates%20the%20feedback%20loop.&text=The%20bad%20news%20is%2C%20even,muddier%20than%20it%20should%20be.

Never said one word about feedback. Gave you the steps to figure it out. Try it on the floor. Good luck.

Last lemming, you have several problems culminating in amplification of rumble. The most significant one is that you are using a very stiff cartridge in a uni pivot arm. Your resonance frequency is too high and you are amplifying rumble inherent in records. You will need to add mass to the head shell. In order to determine how much you will need a test record with resonance tracks like the Hi Fi News Analog Test LP. You want to get that resonance frequency down below 10 Hz. Uni pivot arms are a problem because they have a third degree of freedom and a third resonance point, the rotary one. The best way to avoid issues with rotary resonance is to use a compliant cartridge like an Ortofon 2M series cartridge. They run around 20 X 10-6 cm/dyne. The Nagaoka is 8.5 X 10-6 cm/dyne. It is a great cartridge but it was designed for a heavy gimbal arm. I think you can get the rumble down to acceptable levels by tuning the system. If you can't then there are only three solutions, change the cartridge, change the tonearm, get a rumble filter. My preference would be a new arm. The Nagaoka will work perfectly in an Ortofon arm and they are relatively inexpensive. Soundsmith sells a dandy set of graduated head shell screws. Put the heaviest (Stainless) screws on and tell us what happens! 

I changed out my counter wt from 140 gr to 180 and I added a head shell wt, can’t remember the weight but it was about the size of a dime and about as thick as a nickel. 
No change to the woofer pumping. 
I do have the Soundsmith weights, but they are too short to use on the cart. 

Does the pumping happen with the needle still up??

Last_lemming are the woofers pumping at normal listening levels or just when you turn it up?
The Nagaoka is very stiff and we really do not know where you are.
It would help if you could get the Hi Fi News Test LP. Then we can know for sure. It also is a lot of fun to test other parameters. Very Useful.
Here,  https://www.amazon.com/Tonearm-Headshell-Cartridge-Weights-turntables/dp/B01B8ONJVI and  https://www.amazon.com/Ultimate-Analogue-Test-Lp/dp/B001GBA71Y/ref=asc_df_B001GBA71Y/?tag=hyprod-20&linkCode=df0&hvadid=312149562874&hvpos=&hvnetw=g&hvrand=501746434509243117&h

Woops Wrong test LP. This one  https://www.amazon.com/HIFI-NEWS-Test-Producers-Cut/dp/B00KMCL1PE

another option is get a phono stage with an effective subsonic filter - higher lehmanns have that feature for example

but other advice is spot on... best to find the source of rumble, but it may be coming from the TT/cart itself coupled with records

Not that I think it’s relevant to your immediate problem, but increasing the weight of your counterweight actually has the paradoxical effect of reducing the effective mass of your tone arm, because effective mass is affected by the square of the distance between the pivot and the center of mass of the counterweight. Therefore, when you went from 140 g to 180 g, you then moved The counterweight closer to the pivot to reset VTF. Thus you reduced the quantity that is squared in the calculation. You actually would be better off to use a slightly lighter weight counterweight and move it further away from the pivot. If you want to increase effective mass.

As to your immediate problem, absent undetected and unknown problems with your equipment that none of us are privy to, I suggest you need to move your turntable to another spot in your listening room, and see if that helps. Putting it on the floor like Miller carbon suggested is also a reasonable idea, but put it on the floor in another part of your room, if you can.

Curious as to why and when you changed to BearPaws and what difference you noticed?

Never said what TT support/rack you’re using,?

Just looked at your system page. Here’s my assessment:

I know we have to deal with our own environment but having a tt in the corner/behind a speaker is probably THE worst placement for a tt, especially on a high rack.

I have an inexpensive solution for you, get one more maple shelf just like you now have under your tt and place four appropriate load rated springs between the two maple shelves. If you have access to a drill press, recess the springs 1/8" into the upper & lower shelves. This step isn’t necessary but advised. Thank me later.

Look at my system page.

Also, make sure your two VTA tower screws are tight.

So I’m noticing that on the lead in grooves where there is no sound yet but the record is playing my woofer appears to “pump” exactly once on every revolution. Also the pumping is more pronounced at the beginning of the record vs the end. 
Could have to do with the edges of records being a bit more warped than closer to the hole, but that’s just a guess. 
Is this vertical movement of the arm to blame?  And if so what is the solution here?  I changed cart thinking it was related to compliance, but this cart pumps as much as the last cart, and the new Grado i. Using now is suggested by VPI. 

I could add some wt to the head shell. But when I did that Nagaoka it didn’t change anything.  But I still could try I suppose. 

I could try setting the TT on the ground but presents issues of its own. iC’s aren’t long enough. 
I can’t buy another cart, so that’s out. 

Last_lemming, are you saying this occurs with more than one record??
the lead in grooves seem to be the noisiest park of the record. If this is just one record you have either a warp or a low frequency pulse at one point on the record. No big deal. If it is happening with every record you have a much more serious problem with the bearing or platter. The Cartridge is doing what it is supposed to do. If you are worried about the tonearms resonance frequency get a test record and check where it is. Very easy to do. 

You have two systems.  Have you tried the turntable in the other system?  Same issue there?  If not, I think @slaw may have pointed out what the issue is - placement.

It happens with every record to one degree or another. On the quite passages (lead in groove, etc). That’s why I don’t think it’s a resonant thing. If there is no music how could resonance contribute that much to the pumping.  I suppose the lead in groove could have low freq vibration. 
I will try and do a thorough inspection of platter bearing and arm pivot point. 
You know i do use the 2nd pivot point modification- I wonder if that could be causing the issues?  That’s easy enough check, I’ll just disengage it. 

Given what you’ve said about the rumble being worst in the lead in groove it would be worthwhile to try a periphery ring. I use one and it is very beneficial in terms of vertical movement of the record. 

I recently added the 2nd pivot point to my VPI Classic 2 and it didn't create rumble, nor have I read of any reports of that in the extensive research I did before adding it.  How hard would it be to take the turntable into the other room and see if it has the same issue or not?

Ok. So it’s got something to do with the cart and the tone arm. Which is weird since VPI suggests the cart. 
I have a record that has a bump in the vinyl, the pumping corresponds with the bump.  Weirdly the right channel is pumping more than the rest regardless of how the antiskate is set. 
I’d like to use the calculator on vinyl engine to check resonance, but I don’t know what values to use for the 10” 3D tone arm. 
Does anyone know what I should input to check?