I have a KSW-12 that sometimes makes a loud pop sound when I'm watching a DVD. On LOTR the opening scene where (Sarron) gets his finger cut off, just as the ring goes up in the air and lands on the ground, "POP". Now my sub never did this before. Even during Monsters, Inc "POP" Its like it can't handle a sharp bass punch anymore unless I turn down my sub and reduce LFE signal. Any Ideas? Do I have to return it for warranty service, its only a couple of years old?