my HU has both HPF and LPF slope settings, 1-3 on each. manual doesnt say what db just that there slope settings. ive messed with them a bit and they do make a difference in the sound. from what i understand they are there to blend the speakers together, subwoofer and door speakers. guess im just suppose to set these to what sounds best, seeing as they done have any specific db setting numbers on them, just 1, 2, or 3. is that all id be listening for, what sounds good.