i have a rockford fosgate RFP4210, its a dual 4 ohm sub and an kenwood kac 7251 amp that supposely push 460w X 1 in ohm. just wonder what would be the best way to wire the sub to amp. thanks

 

these are your two options:

parallel wiring


series wiring


that amp is only stable at 4 ohms when bridged. so wiring your sub to parallel isn't a good option. but when you wire into a series, your sub won't see much power when you bridge your amp. you could wire each voice coil to each channel. but if you do this, use a rca spliter split either the L or R on the rca coming from the HU, then connect it to your amp. so it'll be something like:

L-----x (not used)
R------ (use y spliter, run to amp L and R input)

this will let the voice coils get the same signal from the amp. easiest way imo is to get a mono amp.