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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
 
Back testing my cottage system playing SACDs. System is good enough to show the considerable step up from CD sound. Almost as good as my vinyl rips. And like before - with digital sources i see no pumping.
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o_holter OP
977 posts
 
Back home testing woofer pumping on Pink Floyd: The Wall, the dreaded thing happens, my neighbour (house is vertically divided) rings my door bell and asks me to turn it down PLEASE. It happened after I played the "shotgun" drum/bass effects in the intro - "there were certain teachers"...Another brick in the wall. Volume close to the wall to the neighbour maybe 92db.
Since it was early evening, not late at night, I went over to him, rang his door bell, and protested. They have lived there for 4-5 years and not complained before. The dividing wall is sturdy cement you took away some isolation. Etc. But - well - I guess, no more woofer testing, at the moment.
I HATE the feeling that my music "bothers" someone else - don't know about you.
 
atmasphere's avatar
atmasphere
11,874 posts
 
Just as a FWIW- the digital recordings you made may not have the subsonic information that is pumping your woofers, so I would not use such recordings as the results might be inconclusive.
Have you tried greasing the platter bearing yet?
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o_holter OP
977 posts
 
Atmasphere - thanks for hanging on, what would A-gon do without such good advisors.

Today I received the millimeter version tool that should help tighten the housing of the Hanss bearing. When I get my friend over we will turn the whole heavy player on its side and then try to tighten it. We will also give the bearing a bit more oil - this should be just thin "sewing machine oil", says some audo importers over here - Hanss does not specify.

My suspicion is: it won't make much of a difference. But we'll see.

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o_holter OP
977 posts
 
My short summary, so far.
Vinyl rips from my main rig, made on my DSD recorders, played back at my modest cottage system, are able to reproduce subsonic pumping. When I play digital including advanced digital at the cottage system - SACD - there is no such pumping. With vinyl yes, some pumping, varying with the record.
This seems very similar to my findings, regarding my main system at home.
The pumping seems to happen with the cart-arm combo regardless of the player (VPI vs Hanss) - although I have not checked this much.
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