Hello everyone! I am troubleshooting an older Pioneer powered subwoofer I recently acquired. When connected to the "A" speaker output on my reciever the level is minimal with repeated clicking from inside the cabinet, something switching. I removed the 12" speaker from the Pioneer and checked resistance on 200 Ohm setting the reading is 1.3. If I push in on the cone the reading fluctuates wildly from -18 to 43. To test the Pioneer subwoofer amp I attached a passive 4ohm Sony 10" sub to it. It sounds great, but there is a clicking and popping noise coming from somewhere in the circuit board on the Pioneer, like something is tripping, but the fuse is fine. I'm apprehensive of what prolonged use might do to the circuit board. Is something overheating in the subwoofer's amp because I'm using the 4ohm Sony sub? Is the 12" speaker blown and shorting the amp? Any pointers, tips or info greatly appreciated. Thanks for your time. I have researched this particular subwoofer for a long time and can find little info on it.