I used Cardas “chassis wire”. These are Litz stranded and ends *must* be tinned in a solder pot. Cardas can do this but they charge something like $5 per end - ouch! So, I bought a cheap solder pot. My entire project used Cardas solder (which is leaded, I did all soldering outdoors or in my greenhouse). Woofer input is Cardas 15 ga + 17.5 ga (effective 14 ga), output to woofer is 15 ga. Coax input is Cardas15 ga, output to coax is 17.5 ga.