I thought if I set the Low pass from the Head Unit to 80hz it wouldn't send any higher freq. to the amp? Or does the high and low pass filter on the Head unit only correspond to the speakers?

Right now i have two amps. One for my speakers and the other for the sub.

It does sound better when I have the amp set to full and the HU set at 80hz.

 

I have that same HU. My LPF is set at 80 HTZ, +4, 1-2 on the width. I would set the LPF on the amp to make sure (set it to LPF, then crank the HTZ level as high as it will go to make sure it does not cut any extra signals). Also, are you 100% sure you plugged the RCA's into the sub out? I made this mistake initially and it sounded like crap.

Also, make sure the sub option on the HU is "ON" instead of "OFF." If its set to "OFF" the LPF is disabled, which would explain how the signals above the setting are getting through

John

 

If you have full Fc control at the headunit you should set the amps to full range and let the superior electronic crossover in the HU do the work.

 

Thanks for the help guys!! Much appreciated!!!