I'm building a crossover using this schematic that I found here somewhere. Is it necessary to run the negative from the battery to the negative of the LF speaker? I'm going to bi-amp. Also for L4 I couldn't find a 3.5 mH inductor, just a 3.6. Is that going to make a difference? I know you can unwind the inductor slightly to change it's inductance, but I have no way to measure it.