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Why are my woofers pumping?

The other day, with sunlight direct from the side, I noticed that the woofers in my speakers are pumping in and out, much more than I was aware of, when the stylus is in the groove, even between tracks (no music).  I can see it, even if I don’t hear it. Why does it happen? The woofers behave normally (no pumping) with digital music, and when the stylus it lifted from the groove, so it is not the speakers, amps, preamp or phono stage. 

I’ve read that the typical reason for woofer pumping is that the cartridge / arm resonance is too low.  I tested, with my Hifi News test record, and yes, the lateral test puts the resonance at 7 hz or so – too low (but I’ve seen some doubts about the results from that test record).  It is strange, since the combo I use – Lyra Atlas cartridge and  SME V arm (on a Hanss T-30 player) is supposed to work well. I tried to strip my arm of extras, cleaned the damping trough, etc – but it did not help much.

Anyone has an idea, why it happens, or what to do about it?  


o_holter
toddc2
19 posts
 
@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
krelldog
325 posts
 
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.
o_holter OP
980 posts
 
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?

atmasphere's avatar
atmasphere
12,103 posts
 
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...
krelldog
325 posts
 
I think it was the KAB filter....or something similar to that.

I'm not saying its not a good product....it just didn't work for me.
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