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?  


o_holter
Same problem on 3 different Turntables. As a last resort, I bought a KAB rumble filter which I run via the tape loop. I do not notice any less bass and my system really swings. The filter even uses audiophile parts in it. New it was 179.00 but I saw one on here a couple of weeks ago for around 100.00 That, is a good deal. Regardless at what others will tell you, in my system it did not cut the quality of the bass or the deep bass. I can rattle the windows playing vinyl if I want.  The sun has absolutely nothing to do with it.

Ok, the sun was a herring. I thought that the temp might cause a solder break to open a fraction more. It was just a thought.

I've heard of a rumble filter but I have no idea how it works.

These mismatches exist and you’ll never figure out why, nor will you ever fix it. Just enjoy the music. SME V is arguably the best tonearm in the world ever made. And Lyra makes superb high end MC cartridges, even if I’m not the biggest fan.

Rumble filters not only ruin the bass, but suck the life out of the entire system.
Subsonic/rumble filters are crap! You have to use a combination of things 1. record clamp 2. Cart/tonearm compliance 3. Isolation 4.overall setup... I still get woofer pumping but not nearly to the extent it was happening before. I find that using a turntable with a great clamping system (not just a puck or weight) helps a lot to avoid these effects and having the turntable on a piece of granite will be a big plus in helping kill the pumping. Also, finding the right cart/tonearm combo makes all the difference as well. At this level things really need to be in proper order (turntable setup) because things are so sensitive double check table for level, VTF, VTA, ect... 



Matt M