Sorry to you [and the rest of the group] for throwing these things out with no explanation of what makes them tick or why it's so cool to have them tick in the first place.
The items that Redsy is addressing, along with why these filters [and all other AC filters] work is the term "Resonance"
Resonance in Electricity [or any Electromagnetic Radiation, such as Radio waves or Light waves], is very much the same thing that Sound Resonance is.
All things have a "Resonant Frequency". In Sound, if we match the Resonant Frequency of, say for instance a Crystal Champagne glass, we could cause it to shatter. [remember that old Audio tape commercial with the lady singer shattering the glass??].
Anyhow, the Resonant frequency of the glass is the frequency which it naturaly vibrates, like if you were to tap it with your finger. Match it and you make it shake. Shake it at a high amplitude and it shatters.
Well, the Inductors, Capacitors and Resistors in these filters have Resonant properties which, depending on their values, can be figured to Resonate at a certain Hz.
By figuring the frequency you want to pass through them, then finding the value [size] which equals the Resonant Frequency you want, they will "Shake" at those frequencies - which allows the desired frequencies to pass easily, but block others.
So to sum it up, the key on AC filters is Resonance! Shake those puppies at a desired Hz to pass that Hz! [that's the technical explanation
BTW: The Impedance Equalizer included on one Xover is to make the power amp see a more steady Impedance over the complete spread of the frequency spectrum. A Loudspeaker's voicecoil will not always have the rated Z through the spectrum of frequencies it operates on, which throws the total Q of everything to heck in a hand basket [technically speaking].