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
Ag insider logo xs@2x
rauliruegas
9,123 posts
 
@o_holter : problem is that you just noted it and could be many thing. Even that speakers can't reproduce the frequency the woofer movements are affecting the quality level performance of what you are listening.

Even a mistmatch impedances between phono stage and line stage could be ( for whatever reason. ) the source. The electronic very low bass oscilations are more frequently that what we can imagine.

You have to make several tests about because exist no rules to make a sure diagnosis about.

R.
Ag insider logo xs@2x
cleeds
2,065 posts
 
o_holter
Thanks Cleeds, but I don't agree. Please prove the case. Why does the arm kill the cartridge?
The SME V is a terrific arm, but your woofer pumping problem simply suggests you've mounted the wrong phono cartridge to it. There's no reason to suffer such a problem, imo, and using a subsonic filter is treating the symptom rather than the disease.
Ag insider logo xs@2x
cleeds
2,065 posts
 
Question for @o_holter : Did you buy this cartridge used?
If so, all bets are off. You can't be exactly sure of what you have.
atmasphere's avatar
atmasphere
7,068 posts
 
@o_holter 

Raul's suggestion that the cantilever suspension is failing could be an explanation, but the problem I have with that is the cartridge must be pretty new so this seems really unlikely.

I looked at the specs of the ARC used in the review; it cuts off at 10Hz. Your preamp, if still the Io, is only specced to 20Hz (at which point its within 0.25db, suggesting that it can go down considerably further). So its an unknown as to whether that's an influence. Your amps are full power to 1 Hz. I use similar amps in my system at home, but I don't get the woofer pumping, although that was a problem when using the SME5 and has not come back while using the Triplanar (which I see was used in the article you linked, so this problem may not have shown up).

A filter will introduce phase shift, and in a full range system such as yours, will be audible as less bass impact. So its probably best to solve this with elegance rather than brute force.
amg56's avatar
amg56
666 posts
 
@o_holter Does this happen when the woofer and other equipment is not in the sun?
More to discover