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
Holter, The SME V is too light for the Lyra Atlas, a cartridge of intermediate compliance. I suspect you are seeing the woofer take off up between 15 and 20 Hz. Add one or two grams to the head shell and let us know what happens. 
Get a test record with vertical and lateral resonance test tracks and see what happens. 
Hi mijostyn
Too light? I have not thought  that adding mass / weight to the Sme V would help. Seems that the Atlas sounds better without it. The resonance is a bit high - 7 hz ish -  using my hifi news test lp - but to get it down I would rather have to reduce the total arm and cart mass - or am i wrong? I am away now but will test your 'add two grams' proposal soon. Thanks!
The resonance is a bit high - 7 hz ish
That's on the low side. The window is 7-12Hz.
O Holter, the SME V is a very light tone arm. The Atlas/SME combo is fine. 7.5 Hz is a touch low but not low enough to cause trouble. I believe you have said that the woofer pumping is different with different records. 
I'll assume you have not beat your turntable with a sledge hammer. What you are seeing is rumble pressed into the record. The lath used to cut the record is rumbling! I have seen and heard this in a number of so called 180 gm audiophile pressings. Some of these companies are using old hand me down lathes that have been moved around and damaged. If the rumble happens to be around 7.5 Hz your tonearm and cartridge will amplify it. I use a digital subsonic filter. Just for fun I turned it off and played some of those bad pressings and sure enough my subs were flapping around like drunken sea gulls.