Why are my woofers pumping?

Since the problem is mainly gone, the thread should end soon. But it would be nice with a conclusion. I had woofer pumping, I changed some things in my system, and then the pumping (or most of it) went away. Why? Not clear.

Maybe the most likely reason - for now - is that I took out the platter and reinstalled it, with a little change of the ball and spindle position, making the drive work a bit more smoothly.

However my "audio intuition" is not quite satisfied with this explanation. The pumping error seems more like a yes/no proposition, as if you throw a switch - it is there, or not there - maybe mainly resonance-related (or even electric, e g could it even be influenced by static electricity?). So far I have not been able to reproduce the error. So I dont know exactly what makes the woofers start pumping. But it seems fairly clear that if it was only the drive, or player imperfections, the pumping / rumble problems would have been much more constant. 

@o_holter

I too had reduced my woofer pumping with each of the following steps:

1. Cartridge setup tweaked by my VPI dealer
2. Replaced my cartridge
3. Added a Symposium Seque ISO platform
4. Added Symposium VPI footers
5. Added a custom 2" walnut platform sitting on RollerBlock Jr’s under the Seque
6. Swapped my Quadraspire Q4 Evo rack with a Massif Audio Design rack (no obvious change)
7. I have an older Classic 3 and tried damping the arm with VPI damping oil, that didn’t help...

Each of these changes reduced the pumping (well, more or less) and a couple of times I thought my issue was resolved. I think your intuition is probably correct in that this problem might not be resolved.

PM me if the problem returns, I might be open to sending my filter out for you to try.

Todd

I've had that same issue. I bought the rumble filter....it degraded the sound and didn't cure the problem either.
I actually had a post on these forums and someone recommended moving the turntable away from the speakers.
I moved my speakers out into the room as much as I could and the problem was solved. I now rarely get this to happen....and when it does I lower the volume a couple notches and it goes away.
I'm convinced that if I could move the turntable completely away from my my speakers...there would be no issues.
The issue is with your cartridge and speakers. That's my opinion.

The Atlas sounds real good, now, with 100 ohm loading (+1 to Atmasphere). Playing Nik Bartsch: Continuum (great sound) for example, but also older overlooked classics like Joe Walsh: No peace in the city. I love this cartridge. The woofers are energetic, yes, but I cannot see much pumping.
 
Toddc2 - this reminds me of all the tweaking I did with my VPI HW19 - every little bit helped - sand box - ceramic cones - name it. I will take you up on your kindly offer to try the filter, if the pumping persists.

krelldog - I see what you mean - and I also position my speakers quite far into the room. I think best practice is to move the whole stero system away from the wall behind the speakers but thats not very possible, in my case. Which filter did you try?

The interesting thing is: it happens at certain intervals per revolution of the record (playing silent grooves between tracks). If I turn up speed to 45, the pattern is repeated, only faster. This seems to indicate that player rumble or drive problems are NOT the main issue.

Boy, that sure sounds like a drive issue to me!

But it sounds like this is mostly solved :)   I would put a drop of oil on the platter bearing for good measure...