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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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audiotomb's avatar
audiotomb
1,112 posts
 
I had significant woofer pumping

https://forum.audiogon.com/discussions/rumble-issues-see-old-thread-update#1559764

Tried everything

then did the feather test

a light feather should be able to move a tone arm

the bearing in my tonearm wasn't moving vertically

all the movement was the cantilever going up and down creating the woofer pumping
Ag insider logo xs@2x
o_holter OP
977 posts
 
Audiotomb - very interesting. I think my arm floats fine but will check when i get home. The HFN record lateral test shows very visible and sonic resonance ca 7hz while the vertical test is much less obvious (the test tone warbles a bit between ca 10 to 5hz).

"If you have rumble problems, get a light feather!" Who said this hobby was boring?
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o_holter OP
977 posts
 
Update: situation in the system at the cottage seems like with the main system at home. Vinyl records including DSD recordings of these made by the same cart-arm-phono-preamp in the main system, create pumping, more or less. Its not just Meddle, but e g Glass and Shankar too and Sade: Love is... When I play digital from the Oppo player I have here - no pumping so far at least, testing SACD Moody Blues: On the threshold, and CD Spirit: Sardonicus.

There is pumping with vinyl but maybe it disturbs less with the smaller speakers and less linear amp here. I also note that there are more energetic vibration from the vinyl (slightly touching the cones) compared to the sacd and cd. My ears tell me I prefer vinyl - this is why i bother to make recordings. 
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o_holter OP
977 posts
 
It seems that to use the single ended Kab filter from the balanced outputs of my phono stage (having tested that these sound better than the single ended outputs) I will also need a converter box. It becomes complicated.  If KAB was next door of course I would have tried it by now, but it means shipping across the Atlantic and maybe taxes just to have a try. Kevin at KAB has been helpful.
ct0517's avatar
ct0517
2,041 posts
 
o-holter

if you have addressed the turntable, and your amplifier is not blowing its brains out, then it leaves one thing - acoustic feedback. 
what is under the hard wood floors in your room. Do wood beams run under the floor ?   
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