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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?  


Ag insider logo xs@2xo_holter
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o_holter OP
977 posts
 
Thanks. Trying to get in touch with Lyra.
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o_holter OP
977 posts
 
Oh no. Worst case scenario. Trying to fasten the lead clips to the Atlas, to get it back on to the arm, something has gone wroing. Cartrudge first gave strange distorted sound, we adjusted some more, but then it just sailed across the record. Cause - no diamond. It is gone. Without any external hits, stresses etc that we can see. Maybe it just did not like this thread. Anyway it is no longer there. Atlas - caput.
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rauliruegas
13,103 posts
 
Dear @o_holter : Sorry to hear that.  That happened to me twice and I remember that in a trip to Houston in a firned home place just when we wanted to listen his great audio system suddenly the stylus tip just " was not there ", by coincide was a Lyra too: Titan .

R.
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o_holter OP
977 posts
 
Nothing so bad it isn’t some good also. I am trying to find a way out, how to repair it for a reasonable cost. This should not happen, for a moderately used (not misused) cartridge. Such things - diamonds falling off, cantilevers breaking, cantilevers or diamonds not precisely tuned - are known to happen, across cart makers. As users we hope for better quality control and follow-up when sub-optimal units have been sold.

I think we now have a very clear main suspect, not suggested by anyone in this otherwise very rich thread. That is: 1) the Atlas showed increased signs of woofer pumping, over some months. Abnormal, when comparing to the Clavis and Titan. 2) For a short period, the diamond was half-loose from the cantilever, with blurred sound. 3) Next, it broke off, from the cantilever (this happened through normal, careful handling)  All this points to a gradually increasing defect in the diamond / cantilever connection. Assuming that a potential crack or breakup can indeed give some strange bass / subsonic pumping effects at first. I am no engineer, but it seems highly possible, and fits the data in my case.


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o_holter OP
977 posts
 
I thank you all for all suggestions in this thread. My problem of woofer pumping is 'solved'. No diamond, no pumping. No woman no cry. Maybe, it was mainly a result of usage. It has 1200 or 1300 hours use, in my estimate. I will try to fix the Atlas. But this thread is now at rest from my side, since the problem is gone.  
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