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
Testing DSD recordings made by the same cart-arm combo on a different player, the VPI HW19, some years ago. Not quite the same, since the recording was made with the Lyra titan i cart, not the Atlas. Yet they have the same compliance and should behave fairly equal.

Is there woofer pumping? Yes some. A bit less? Maybe, not sure yet. The jury is out.

Listening to my older recordings, I hear a poorer recording and flatter, more restricted sound than with my current Tascam DA-3000 recordings (and direct vinyl playback). Not strange, these recordings were made by the little Korg MR-1, punching above its class, but still limited, with single ended connections while I now go balanced, to the Tascam. My general impression is: when I went from standard DSD recording (Korg MR-1) to double speed DSD (Tascam DA-3000) I clearly got better sound and more bass. But maybe a bit more woofer pumping too? I am not sure. I will have to check this out.
Conclusion so far - maybe, just, live with it, until the next cart change.
Facts:
- Pumping carried over to the secondary system - clearly not amp or speaker dependent (digital LP recordings).
- Arm bearing, turntable, drive, belts etc - no indication of misbehaviour
- Maybe the leeway in the Hanss bearing plays a role, I will know soon when I get the tool to tighten it (i doubt it makes much of a diff, based on testing so far) - including: if the Hanss misbehaves, why do I see pumping also on my VPI HW19 recordings - ?
- Getting a balanced filter seems difficult. E g the KAB single ended filter would need an extra box. This combo (or cludge) would probably not be good for sound quality, compared to direct balanced.
- I suspect that a rumble filter, properly installed (in the phono stage) might help my sound.
- I see woofer pumping clealry before or between the music tracks on the LP, with the stylus in the groove. This goes on more or less, depending on the LP. The pumping is clearly related to the revolution of the record, it repeats once per cycle.
- When the music is playing and the stylus in working within the music track, I don’t see much pumping. I suspect that this is because the woofer is now in the grip of the musical energetic vibrations.
- However, it may be that the woofers are still made to "work" down below in ways not optimal to the sound. In simple terms, more stress, less peace. Not sure.
- I have a feeling that woofer pumping is related to more listening fatigue. But I am not sure. Testing different records, I also find a bit of the opposite rule - pumping is related to good, involving sound.
- If I had serious "underlying pumping problems" with analog/vinyl, I would have selected the digital source, in my system (since digital music shows no pumping). Yet that’s not the case. Digital music sounds much poorer in my system. More harsh and flat - and not much more "peaceful". Although this may also be due to the fact that my analog chain is better than my digital chain.

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.
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?