If the sub farted, but the speakers still work...then it's probably a poor contact on the subwoofer driver.
If those are any bit similar to the Stereo version of the S-80, then the amp for that system is inside the subwoofer, so it either lies in the wire going to the woofer, or in the woofer itself.
Those speakers are a pain in the rump to open up. I had to service the volume pot on my old stereo S-80 set...that was unpleasant. Just be patient, and have your computer up, and document EVERY step you take to open it up....it comes in handy later if you are having trouble putting it back together, trust me on this.
Once you get it working, you will probably like them. Just make sure the subwoofer is down around your feet...it IS directional, due to the frequency limitations of NXT panels the size of the satellites on that system.