Anyone wish they had a rumble subsonic filter?

A good rumble filter will attenuate differential signal, which is vertical groove modulation, without affecting horizontal modulation. If you have a single subwoofer (or two) driven in mono (mixed Left and Right) this will solve your problem. I bet you could Google "rumble filter" and find a diy kit.
By the way, the pumping of your woofer cones does affect the sound although you may be used to it and not notice.

I have KAB's rumble filter ($170) and it completely solved my problem. At first I didn't understand why my woofers were going nuts, then once I finally learned what the problem was, I was able to get a separate rumble filter and life is good.

Michael

Dear 240zracer: The Eldartford suggestion: run the subwoofer in mono way is really the best one because you don't have to add any other " stage " ( rumble filter ) to the signal.

Like Eldartford already posted the pumping in your woofer cones are adding intermodulation distortion and certainly makes a degradation to the signal reproduction.

Regards and enjoy the music.
Raul.

Couple of things guys. This is a three-way stereo speaker, not a subwoofer. I just looked at the KAB. It turns everything below 180Hz to a mono signal. Seems like a rumble filter should only operate from about 18Hz down like the ones on my old integrated amps used to do.

I was going to add a high-pass filter at 18Hz to my woofer crossovers, but that passive method requires some very large caps and inductors. Might have to revisit that. Also noticed the Bellari phono preamp has a rumble filter. Pretty nice feature on an inexpensive unit.