I understand how to use the reactance equations (for capacitor, xc=1/(2PiFC), & for inductor xL=2PiFL when the filter circuit is of first order to get the component values I need, but I don't understand how the math works when the circuit is of second order. The man at the electronics store told me to simply put boxes around the components, treat them as resistors, and solve. Okay, so for the capacitors I did that in figure #2 & or inductors, see figure #3. That's what I don't get. When resistors are in series, you simply add them. When in parallel, it's 1/Rtotal=1/R1+1/R2 ... This is a series-parallel circuit though! I watched some Youtube videos titled "series-parallel resistor circuits" & they simply... uh, let's suppose you have one resistor, R1, in series with 3 resistors, R2, R3, R4, that are in parallel. The Youtube mentor ignored the singe resistor R1 in series & focused on the ones in parallel, so R2, R3, & R4. He combined them, drew a big box around them, & called it R2. Then all that was left was R1 and "R2" which were now in series. Simple, yeah. But, in my circuit, there is a load present. Wouldn't that matter? So is it really just R1+R2? I can't decide whether or not it's a series circuit. Yeah the two resistors are in series, but not with respect to the load (the speaker) And how does this all fit into the reactance equation? So for capacitor, you have xc=1/(2PiFC). Would I simply solve for C, then take that figure toss it in the parallel capacitor equation? Lastly, the instantaneous impedance listed at each speaker, the tweeter 4 ohm, and woofer 4 ohm ...well I lied. Tweeter is more like 3.3 ohm around desired x over point and wooer ...well the manufacturer decided not to include it to keep people like me from getting decent results I guess? How is that going to work? Now how in the world does that work with the reactance equation? XC is no longer 4 ohms.