Rippling cones

@hleeid,

I use the KAB rumble filter that the Cable Co sells, but I bought mine from KAB.  Your Rega being lightweight is not the problem.  My 40+ pound VPI Prime suffered from the same problem.  After trying a 4 inch thick maple slab, springs, pods, wall shelf, etc. I bought the KAB and have zero problems now.  
I have been using mine for 7 years and it is dead quiet, no noise, no hiss no nothing.  I run mine through a processor loop  on my preamp.  It is money well spent.

hleeid, you wouldn't. Feedback sounds like a howling noise. A cartridge that is too compliant for the tonearm can make this worse. A stiffer, less compliant cartridge might calm it down a little. If you want to know what is the environment and what is on the record simply put your stylus down on a stationary record and turn the volume up. Walk around the room watching the woofers. Jump a few times. This is the environment. What you see playing the record is a combination of the two. 

@cleeds , I respectfully disagree on this one. I have a number of records on which the rumble is atrocious. All records have some rumble to an extremely variable degree from almost dead quiet to ridiculous. The worst have been done rather recently, I suspect on poorly maintained older lathes. The rumble is usually rhythmical so I know it is the lathe. One record had me convinced my bearing had gone bad. 

As we have seen on a number of threads, low frequency trash can cause a lot of trouble with little cones. The LS 50s do nothing under 50 Hz so I would use a high pass filter set there and not only will the rumble stop but the speaker will get a lot cleaner and go louder safely. The other solution is to use a digital two way crossover and cross to subs at 100 Hz. MiniDSP makes a wonderful inexpensive one. Isolating a turntable is important but it will not fix this problem. This occurs with all systems but those with large woofers and subwoofers do not notice it as much unless they play really loud. Even so in a powerful full range system a high pass digital filter set a 18 Hz is a wonderful thing. You can use slopes as steep as 10th order without harm.

@noromance - have you tried either filter? quite the price difference!

Only the KAB when I had a LP12. Don't use any now. Using springs instead.

@stereo5 

Your Rega being lightweight is not the problem. My 40+ pound VPI Prime suffered from the same problem.

Only a problem weighing down the springs!

@noromance 

True enough.