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
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.
 
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?
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.

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.
My audio friend Eirik came around today and helped me tighten the housing of the spindle on the Hanss player. Luckily the needed 2.5 mm Umbraco driver was included in the set I had bought. So - what was the result? Pumping: no difference. It did not go away. Sound: maybe a tiny bit more relaxed, less tense, but this may be my imagination. Eirik brought along some fine-sounding records and we played tracks from the Mofi edition of Dylan's Another side, and from the reissued Grateful Dead Cornell 1977 box. They sounded very good, and neither he nor I could find any clear indication of too much rumble. But he did remark on the LOOKS - the visual (subsonic) pumping of the woofers especially between tracks. It does not look like that in my system, he said.