HU is a Kenwood kmm-bt318u. Only 2.5v for preouts but I have had the HPF set at 100hz for front and back, tried 150, and I've tried at 250. Right now I'm keeping them at 180hz with a slope of -24db and I still get the noise. The old 4 channel was a Hifonics brutus 616.4 and I swapped it out just...