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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?  


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Showing 1 response by mattmiller

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mattmiller
1,479 posts
 
Subsonic/rumble filters are crap! You have to use a combination of things 1. record clamp 2. Cart/tonearm compliance 3. Isolation 4.overall setup... I still get woofer pumping but not nearly to the extent it was happening before. I find that using a turntable with a great clamping system (not just a puck or weight) helps a lot to avoid these effects and having the turntable on a piece of granite will be a big plus in helping kill the pumping. Also, finding the right cart/tonearm combo makes all the difference as well. At this level things really need to be in proper order (turntable setup) because things are so sensitive double check table for level, VTF, VTA, ect... 



Matt M



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