I'm going to start of by explaining what they are and how they work. This is going to get a little deep at times. But if you have any questions feel free to ask I will try to make it as basic as possible.
Okay now for the basics there are three basic kinds of passive crossover networks. Low pass, High pass, and bandpass or pass band which is actually a combination of the high and low pass.
A low pass consists of an inductor or coil also sometimes called a choke. As the audio signal passes through them and the frequency rises the inductive reactance of the coil rises. Which means it becomes harder to pass the signal through the coil effectively cutting off or choking the the high frequencies beyond the predetermined crossover point. All this junk means is that a low pass crossover will allow frequencies below the crossover point to pass, but chokes the frequencies beyond it.
A high pass crossover consists of a capacitor. Which does the exact opposite of what a coil does. As the frequency decreases the caps reactance increases. Which filters out the lower frequencies. All this junk means is that a high pass crossover will allow the frequencies above the crossover point to pass, but filters the frequencies below it.
Now a bandpass or pass band ( how ever you want to say it ) is a combination of a coil and a capacitor ( low pass and high pass) All this junk means is that a band pass filter allows a range of frequencies to pass above a selected crossover frequency and below another selected crossover frequency, filtering out all frequencies outside of this band.
Any questions so far ?