Nice to see my last post was ignored.
Joe: I've measured the voltage drop from the alt to the battery/ fuse box positive. Its about a third of a volt. I lose another third of a volt going back to my distribution block in the trunk. So at the amps I'm at 13.3 V with the alt putting out 14 V at its output terminal.
Dimming in my car is typically noticeable when the voltage drops below 13, say 12.5 V. In the neighborhood of where the battery starts to add current to the system. The only thing that brings the voltage down this low is holding at least two of the window buttons down when the windows are already fully closed or opened. (I realize this damages them hence not doing it for more than a split second if I can help it)
The question is, do you have dimming exactly when the bass hits in your music? Or does it come and go?
It seems like you're asking too much from the stock alt.
My system pulling 100% of its supposed wattage ratings, should be asking for 1080 watts and at 13.3 V that'd be 81.2 amps. That leaves 30 amps for the car to run granted the alternator is putting out its full rating. Which isn't likely considering i keep the rev's as low as possible which means lowest output from the alt possible. Also, when the alt heats up, it puts out less.
Now... Crown, a reputable supplier of pro amps, suggests that severe clipping occurs at 1/3 continuous power output which means my system only draws 27.1 A when running full tilt.
If you're pushing your amps to their limits, they're going to draw rediculous amounts of power and your alt just isn't capable of dealing with that.
If you have a true 650 watt amp and you actually get 650 watts out of it, and its class A/B, its drawing between 1000-1300 watts. depending on the voltage (13-14V), thats 100 to 71.4 amps of current. I'm not sure your car can run on 25 amps, I'm a little doubtful considering how much crap cars have to power these days.
So the real answer would be, get a HO alternator and upgrade the wiring to handle your higher output alternator.
