I have an exact cabinet copy of the JBL B-460. I set it up in my home theater with a re-coned 2445. I drive it with an Adcom 555 in bridged mode. When a DD movie puts out high volume to it it will put out an awful rumble. The cone appears to move clearly. I tried a 2440 and had no problems. I'm guessing that perhaps I have an electrical feedback problem? I was thinking of an 8-50 ohm damping resistor in parallel? Perhaps a problem at resonant frequency and might need a series resister,cap,coil in series tuned to the frequency? Any ideas or suggestions gentlemen?