I currently have a 12W0 8 ohm JL sub powered by an old Pioneer receiver. Because I have no crossover on my receiver (Dolby Pro-Logic so no LFE), I've been thinking about making a passive crossover for the sub. From what I understand from the little reading I've been doing, I have to wire a coil in series to make a first order lowpass filter. I'm sure it's probably way more complicated than that, but for me it's a start. What I want to know is if anyone can point me towards a website that goes into the specifics about what I needto do to make a passive lowpass filter for my sub. Thanks.