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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

Showing 2 responses by toddc2

toddc2
19 posts
 
@o_holter - You mentioned earlier in the thread about an XLR filter. I was struggling with the same woofer pumping problem and finally commissioned Dan Satoni at DTS electronics to build a custom balanced high pass filter for me. Problem solved with no obvious loss of sonic performance. I know Dan has a minimum board order of 5 units so I am pretty sure he can quickly build another one for you if interested. It wasn't exactly cheap ($550 CAD) but I feel it was an exceptional value at that price.

Todd

VPI Classic 3 w/Lyra Delos -> Whest PS.RDT30 SE -> Custom Filter -> ARC Ref2 MkII -> ARC VT100 MkIII -> Magico S1
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
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