2. analog
  3. 135607-5312

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
o_holter OP
980 posts
 
Thanks, all!
Atmasphere - you may be right. But Lyra does not warn, and web debate does not complain, using the Atlas on the SME V - so i wonder.
Czarivey - good suggestion, but I doubt speakers or airborn feedback is the cause. Sounds (looks) much more "physical".
Invictus - yes, I see what you mean, but investigating more, using my eyes, plus my finger on the woofer cone, and my ears - my feeling is, this pumping has messed up my musical image. The SME V has an effective mass of 10.5 g I think. The Atlas has a compliance of 12. The calculators I’ve tried pushes this into ca ok "green" 10 hz territorry. Am I overlooking something? Is the Atlas really ca 22?

atmasphere's avatar
atmasphere
12,171 posts
 
Atmasphere - you may be right. But Lyra does not warn, and web debate does not complain, using the Atlas on the SME V - so i wonder.
It might be that some of those debaters don't have the bottom end bandwidth in their systems that yours has.

I went from the SME5 to the Triplanar and that helped get rid of that problem in my system. The SME5 seemed like it was a higher mass arm than the Triplanar. 
o_holter OP
980 posts
 
It is a long-term discussion -
https://forum.audiogon.com/discussions/how-to-change-effective-mass-of-a-sme-v
Atmasphere, isn’t your Triplanar arm mass higher than the SME V?
I should get the arm mass down, to get the resonance frequency up - true?
Increasing the arm mass is not difficult, decreasing it is the trick ;-)
cleeds
6,272 posts
 
I agree with @atmasphere that cartridge compliance is almost certainly too high, although placing the turntable too close to your woofers may exacerbate the problem. Short of replacing the cartridge and/or counterweight, you might also see if you can lessen the problem with damping. You write that you "tried to strip my arm of extras, cleaned the damping trough," so it’s not clear that you’re using any damping at all. Is that correct?
cleeds
6,272 posts
 
atmasphere
It might be that some of those debaters don’t have the bottom end bandwidth in their systems that yours has.
That’s possible. It’s also possible that the debaters have absolutely no experience with the arm, or with your arm/cartridge combo. There are many self-proclaimed vinyl "experts" on the web who have no idea what they’re talking about.
More to discover