Originally Posted by chalugadp
Here it is
Maybe I'm the only guy who just knows what capacitors and resistors do
Hopefully I get this all right. I can't make out all the parts, so if I screw up something sorry about that. And these aren't gonna be in numerical order, because it'll make more sense this way.
2 & 6 go together on the woofer section. They're very simple. Just a 2 pole 12db/oct filter that starts around 400hz. The capacitor can be sized bigger or smaller to vary the slope a little bit. The inductor sets where the woofer starts to roll off.
5 & 11 Are tweeter resistors. The first one going into the tweeter circuit attenuates the very high frequencies and the last parallel resistor brings the whole tweeter level up or down. The las parallel resistor also flattens the impedance that the rest of the circuit reacts with.
10 & 14 make up the tweeter filter. Just like the woofer, this is a two pole 12db/oct filter. But in this case the cap sets where the roll off begins and the inductor can vary the shape/steepness. In this case, it starts to roll off around 3khz if I recall correctly and the inductor kicks in around 2000hz to shape the response a bit. XO at 1750hz. The numbers aren't exact. I'm going by memory. And this filter is also used to attenuate a peak in the response, so it's all a little confusing.
Now the mid section.
13 This big cap is a first order high pass filter starting around 1khz reaching -6db at the woofer XO around 650hz iirc. This is a fairly significant component.
8 & 12 These are the first parts of the low pass filter. Mids have a high pass and a low pass filter (commonly called bandpass filter). The inductor is the first pole in a 3rd order low pass filter and the cap is placed in parallel with this inductor. The cap steepens the filter and puts a notch in the response right around 7khz iirc. Basically, I was trying to shut the mids up very quickly above 2khz because side by side mids have major issues. So I need to slam them into shape, and these parts are the first of that.
7 & 9 are the second pole in the low pass filter. The cap is actually, the 1ohm resistor just damps its effect. It was size to provide a bit of boost right around 1.2khz where the mids had a hard time keeping up with the woofers and tweeter.
3 is the third and final pole in the low pass filter. Nothing special about it, except it was sized to star reacting right around the XO point iirc. I dunno. It was sized to get the shape and phase where I needed it.
1 &4 Perhaps the most interesting part of this XO actually. Single order high pass filters never work because as soon as you get to the Fs spike in the impedance, the filter is useless and your power handling goes to hell right at that point. That's about 150hz in this case. So you can either make it second order, or nuke that Fs spike with an LCR notch. Second order just wasn't working for me and an LCR is quite expensive because it uses an even bigger inductor and a huge cap. So what I did was just use this inductor and resistor to manipulate the mid's impedance. It makes for something like a 9db/oct roll off actually instead of a true 6db/oct. But that gave perfect summation (phase) and good power handling. And was very cost effective.
There you have it. All my secrets.
Hopefully it made sense.