I have 1 12 inch Memphis m5 with a jl audio 500 watt amp pushing it everytime I turn the volume up it hits but then starts going in an out I have it grounded straight to the body of my car with a 4 gauge pos an neg also have a 300 watt fuse even tried a capacitor but still did it. All set up as 1 ohm I even tested the amp with a multimeter an it never went below 14 volts. Any idea what's making it do that