Originally Posted by RonRizz

Its not as complicated as it sounds.... Briefly put, (or as brief as I can make it) Human hearing is 20 hertz to 20k hertz. There are 10 "octaves" therein. (frequencies) To move up the scale one full Octave is to double the frequency. so your octaves would be 20, 40, 80, 160 hertz, and so on... up to 20,000.
Component speakers are designed so the proper frequencies make it to the proper speakers. They do this with crossover networks, or "filters"
Low pass filters leave frequencies below their point through to the speaker
High pass filters leave frequencies above their point through to the speaker
So in a typical setup, A Subwoofer will see 20 to 80 hertz. A low pass filter keeps anything over 80 hertz from getting to the Sub.
A Midrange will use both a high and a low pass filter. 80 hertz high pass, and 3200 hertz low pass. This means the Midrange will see frequencies from 80 to 3200 hertz. A tweeter will get a high pass filter at 3200 hertz, so it only sees frequencies at 3200 hertz and above, to 20k Hertz.

So in this setup, my crossover points are......80 Hertz, and 3200 hertz.
A crossover "slope" is the number of decibels a filter will allow to pass for every octave beyond that set point. they are typically at 12 decibels per octave. for example, lets say you are playing some music at 100 decibels. because your Subwoofers Low pass crossover (filter) is set at 80 hertz, your subwoofer will see frequencies above that, but at a greatly diminished amount. (in this case 12 db per octave) so your next octave is 160 hertz......100db minus 12db=88db, next would be 320hz.....88db minus 12db=76db....easy peasy.
Realize that a difference of 3db in volume is much bigger than you think.