JBL PB12 subwoofer: Good Bass but bad electronics We got this subwoofer as part of a home theater purchase from craigslist. I have been generally pleased with the bass it puts out for its size. It basically has a single 12" subwoofer which fires downwards and is ported to the back of the cabinet. The subwoofer does have a good set of features. It can accept speaker level inputs, RCA inputs or even the regular LFE input. There is a phase control switch, a cross over frequency knob and a level knob at the back to really fine tune the bass output. When it works, this sub does great. however, I recently found out that there is a problem with the amps in this subwoofer. At times, it will make a popping sound when turned on or off and it can randomly turn off. I called JBL but they say replacement amps are not available. In the event the amp does stop working, I have a feeling I might have to try using an external amplifier as the subwoofer can still be used.