My 8 year-old Mission 8" powered subwoofer has started popping under load. I was watching a hockey game and the subwoofer started "popping" almost like it was clipping. I checked the speaker cone and it was intact. The crossover is set to 80Hz on the speaker and the volume control is set to about 60%. Changing the crossover frequency did nothing...changing the volume control, however did. Higher, it popped more. The Audyssey setup has already been run. I ran the Test Tones and it "popped" as well. Only noticed this once after I ran the Audyssey and ran the Test Tones, so I reduced the volume of the Sub. The Sub never popped at any time in the last 8 years with my old JVC which had a fixed Subwoofer output signal and I ran it pretty hard over the years. My old JCV was rated at 100 Watts RMS per channel...this one is rated at 75W but I don't think this refers to the Sub signal. The Audyssey Dynamic EQ and Dynamic Volume were "on". I also noticed that the cable connection on the receiver was quite loose...I could turn the RCA connector extremely easily. Any idea what is happening here? Thanks.