I just got my Jl Audio Amp 300/4. I just got it all installed and hooked up. What I was wondering is whether or not its better to use the Crossover built into my Alpine Head Unit or use the Crossovers built into my Amps. I have the Alpine 9831 HU, JL Audio 300/4 amp, and JL Audio E1200 for my 10" sub. Does anyone know about the 12db/24db filter setting for the crossover on the JL Audio's? What range should I set my LPF/HPF's at? I have them both at 80Hz through my Alpine HU crossover and I have both of my crossovers turned off on the amps. Please let me know what you guys think. Sorry for being such a newb.

 

Either x-over will work just fine. If you set it at the amp, you don't have to worry about re-setting it via the HU if you ever lose power to it.

The 12/24db setting refers to the slope of the x-over, per octave. A 24db per octave slope is much sharper than a 12db per octave slope. This means that the cut-off for frequencies sent to the sub will be sharper at 24db than 12db. How to set it depends on numerous variables, including vehicle accoustics, sub response curves, mid-range driver response curves, etc. Good news is, it doesn't cost anything to experiment...

EVERYONE is a newb once, so don't be sorry. You don't mention what door speakers you are using, so I'll tell you how I set mine up:

I have my doors set to x-over at 80 HZ, with an 18db/octave slope. This prevents really low bass from making it to them and causing distortion. The subs are crossed over at 100HZ, with a 24db/octave slope. This allows me the best SQL and SPL without having audible distortion.

Good luck and keep posting...

 

Thanks for all the good info B-man. Right now I have the Alpine Type R door speakers in the front and rear. I did run into a little bit of a problem. My HU pushes about 4v into the RCA's coming out of the back at higher levels. My amp has a setting for Low Input (up to 2v) and a High Input (up to 8v). I'm kind of split between the two so either I have a dominant mid to high range or a dominant subwoofer. I read on the JL Audio sight how to calibrate the Input sensitivity and they mention using a CD with a sine wave test tone of 0db reference value at various frequencies for the doors vs. the subwoofer. Does anyone know where I could possibly download these tones? I will try out your setup once I get the input sensitivity tweaked in. Again, thanks man.

 

Of course you can do the " timley " thing, trial by error.
By messing around with the xovers on both your HU and amps, you may find pure audio bliss.
I had my system in for about 3 months, it sounded great. One day, cleaning up the garage, I found my HU manual. I didnt realize HALF of the functions and features I had been missing out on. It just opened a door to a whole new world of listening enjoyment. Try different settings, and amp xover combos. Who knows?

 

to do sine wive or pink noise you would need a rta to find the flat curve then set crossover and eq settings