my friend has a stock headunit and is getting his signal using only one side of the high input from only 1 speaker in the car and he has 2 4 ohm 15s bridged at 2 ohms to only the 2 channels that are hooked up and it was working fine yesterday and today he said he turned it up and it went into protection.ive never had a 4 channel before and im not sure if i can run each bridged pair at 2 ohms