Crossovers, and other weird bits

[big_steve_x]

what are cross overs, what is a low pass filter etc high pass filter, what does my amp need to do to power 2 subs, and how do i power tweeters, an amp or sumthin?
and lastly, whats this 2 way 3 way and 4 way thing about
oh an a really basic question what size speakers go into NORMAL nova doors?

[adam5]

speakers in nova doors
======================
use 6.5 inch
low pass filter/high pass filter
================================
low pass filters out any high frequencys (i.e. only lets low noise through = good for subs!) high pass filters out low fequencys (i.e. only lets high freq noise through = good for mid/tweeters
amp to power 2 subs
===================
two channels or the ability to run in series (or is it paralel my electronics is a bit dusty)
cross overs
===========
split audio signal up dependant on frequency.

hth