How to fix woofer pumping

move speakers farther away from turntable.

Sounds like the arm and cartridge do not mate well.

Sometimes you don't have the option of moving your turntable - or anything else, for that matter.

I got the KAB rumble filter - and believe me, it works like a charm.

It does not have the slightest effect on playback.

Thanks all for the responses.

Anyone have any information on how to tell if the arm/cart are a good match?

Check your cart alignment.

Putty, if the mechanical resonance of the arm/cartridge arrangement falls outside of 7-12Hz, you will have problems. I don't recall my arm theory all that well but on one side of that window you can get pumping effects. The resonance is a product of the effective mass of the arm, and the compliance of the cartridge (which would be too high if you have pumping). Intuitively, it seems to me you will need to reduce the mass of the system somehow, or go to a cartridge that has a stiffer cantilever.

The *other* thing that can cause pumping is weak filter caps in the electronics. If this is the case you should be able to maintain the effect for a few seconds or indefinitely upon lifting the arm off the LP. Try that before anything else.

Putty, you might check out the cartridge database, they have a wealth of info and helpful calculators. There is info on cartridge and arm compatability there.
http://www.cartridgedb.com/