This is a wiring diagram for Series-Parallel wiring for DVC (Dual Voice Coil) subs.. That means the voice coils on each individual sub are wired in series, the the subs are wired together in parallel. To calculate impedance for Series-Parallel wiring, enter the impedance of each vocie coil, the nuber of subs you are wiring, and then hit calculate. Hit reset to clear the fields.