Ground loop or shorted speaker?

[TheUgster]

Howdy guys, just installed a pair of Infinity Kappa 5x7s in the front doors of my truck, along with a new headunit. I took my time, soldering and heatshrinking all the wires for the harness, and carefully installed the speakers. When I turned the system on (KOEO), I heard static from the passenger side, and when I started it up, ALTERNATOR WHINE. I unscrewed the right speaker again, set it on the floor, turned the system back on... No noise. I went to reinstall the speaker with the key in the Accessory position, and the screw made tiny sparks as it contacted the speaker screw hole and door.

Again, this is only on the passenger side. It doesn't appear to do this with the old speaker, however that one was original to my truck, and as such was in pretty poor shape. Thusfar I've checked the resistance of all the wires going to that side, everything from the head unit to the wiring looks good. I took the passenger footwell cover off, and realized that the negative speaker wire grounds to the chassis. Is it supposed to be this way? I was under the impression that both wires had to go back to the HU first, which was grounded thusly. Let me know what you guys think, I'm really scratching my head here.

 

[Psychopete]

check the ohm load between the speaker terminals with a multimeter while it's disconnected

 

[Loud Ranger]

it shouldnt be a common ground like your describing, is that the only speaker that is grounded like that? My vote goes to running some new wire just to know its right. The hard part is getting it thru the rubber elbow in the door but a coat hanger helps a lot.