Again, an "active" sub is just being powered by the amp in the same box. The wiring is exactly the same. The amp is powered, and has a remote cable to switch it on/off with the car. The amp then just has 2 wires going to the sub (in most cases) which sends a current to move the cone.
If you buy separates you'll have a sub that literally just needs amped + and - wires connecting.