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?
