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I have 2 psi platform 2 wired to 4 ohms with a pioneer 3700bhs and I'm trying to find out what's a good crossover for the subwoofer? I have it go as high as 80hz but my question is can I set it for higher like 250hz? Like would it be efficient or not

So I got a new car and put my old setup in (skar lp1000 monoblock, Jensen w12 4 ohm single coil, 4 gauge), whenever I turn up the volume slightly my amp goes to protect. Multimeter says battery isn't dropping voltage but when I check at the amp I can drop from 12 to 9.5 on a small bump, ground...