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
Update: I have got a replacement for the broken cartridge, and I am very happy with the performance.

Some testing: The new Atlas makes it clearer that the subsonic effects (and possibly, the subsonic woofer pumping once per revolution) is part of the intended sound, e g in the introduction to Pink Floyd: Echoes. It resides in the recording (or my pressing) and is not in a fault in the system, even if the resonance frequency of my arm and cart is a bit low / challenging, so everything happening down at the end of the frequency scale is picked up.

I don’t hear much rumble or other unwanted effects, just a marvellous big soundscape.

On Rickie Lee Jones The evening, I no longer see any clear subsonic woofer pumping, just a lot of energy, in the woofers, coherent with what I hear.

So it seems, especially with the new Atlas - just look away from eventual woofer pumping (as long as the woofers don’t complain), give it a go, and enjoy the superior sound.

Pink Floyd’s Echoes is known to include "subsonic" effects. Maybe once per revolution - like they later experimented with heartbeats, on Dark side...or maybe on Echoes this is a not intended side effect, who knows. I have an early second pressing of the Meddle UK original, matrix side 2 (with Echoes): "SHVL 795 B-6" "11"? "1" and handwritten "HTM". HTM means Harry T Moss cutter extraordinaire at EMI UK. I have read that subsonic effects may happen due to record warp, but I cannot find any signs of this, with my copy.

Does it sound good? You bet!
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.