doesnt have one.... bought it from DaGh0st... figured it out though... theres 3 slots for these jumper things... there's 4 slots for power wire. The 2 outside slots for the jumpers makes the subwoofer's voice coils wired in parallel, while putting a single jumper in the middle with no others makes it series. On the power wire holes, there's one that has in very small writing "series +" and another on the other side that says "series -" So i put the wires where they need to go, and the jumpers are pretty neat, no more extra wire needed, wire it just like a svc sub. Very happy with the sound output on such meager power. I would like more output from the 80-140hz range though, but i think i need more power for that.