Woofers getting workout, but no bass

The cause of this problem is most likely very simple. Is the woofer pumping worse at the beginning of the record and then lessens as the tonearm moves toward the center of the LP. If so, the outer edge of the LP is probably not coupling with your platter. You may even be able to see light between the outer edge of the record and the platter when viewed on-plane from the front.

If you are using a clamp, try lessening the downward clamping pressure to see if that helps. If it is a problem with LP/Platter coupling, the best solution is a peripheral ring (like the one sold by TTweights and others), but some say that these rings deaden the sound as well. I don't have one so I don't personally know about that.

If the pumping occurs across the entire LP, then Cpk likely has indentified the cause(s) above.

Good luck.

Madfloyd, you system thread lists TW Acustic Raven One as your turntable.

If that's the table playing and your woofers are pumping it's not due to rumble. The Raven is a quiet turntable with very low rumble but it could be susceptible to mechanical feedback which causes low frequency pumping you describe.

Many turntables are sensitive to vibration from footfalls or speaker bass output. How was your Raven set up, a professional familiar with the product? What kind of stand is it resting on, and is your floor completely solid or perhaps pier and beam (suspended).

I may be way off on this, but if your woofers are moving like crazy, you should be able to hear it. If you are not hearing the bass, maybe your listening position is in a null. I have measured a 10db difference in bass by moving my listening position back 1.5 ft.
Is it possible for a woofer to be moving like mad, but not being able to hear the "subsonic" frequencies they are creating? My woofers are behind cloth at the back of the speakers so I can't see them.

you are experiencing a very typical phenomenon as Vegasears suggests. Only a filter that eliminates those lower frequencies will eliminate this. I would venture to say that the other possible causes mentioned may play a diminuative role also. Seek out an inexpensive filter online and try it out for you to see. Then, after concluding that this may be the case, you can start getting the typical audiophile paranoia of whether this is now altering the overall signature of the music.

Rumble filter
http://www.kabusa.com/rf1.htm