LP - Low Pass. It starts cutting frequencies by <x> dB/octave, above the frequency you set it to.
HP - High Pass. Same as low pass, but it cuts the frequencies below the frequency you set it to.
OFF - Probably self-evident, but that will be full-range.
You want HP. That will protect your mids from over excursion that will occur when they try to reproduce lower frequencies. Just set it to 100 Hz or so, then slowly take it down 'til you hear a bit of distortion, and then back it up a little. You'll probably want to do the one set of speakers, then set the other ones the same.
If you have subwoofers, you don't need the other speakers to produce the lows that the subs will take care of. You also will be able to run less power to the other speakers and not clip your amps or damage the speakers since producing low freq's uses lots of power and creates lots of heat that could damage speakers not designed for low range output.
My wife thinks I'm crazy when I'm talking to her in the car, suddenly make a pause and start analizing if the sound is perfect. I'm like : did you hear that?! that sounds right to you? I better make some changes! Man. I wasnt like that, AT ALL
I started with the intention of spending $200 and now I'm over the $1500. Thanks ecoustics forum ! you changed my life, and it was totally worth it !
