Car Stereos: installing amp, ohm subwoofer, mono amplifier

Question
I have a 4ch amp head unit has front and rear outputs how can I hook a sub to that also using the same amp also how can I tell which speakers wires are front and which are rear in my chevy silverado 1500

Answer
Hi,

Generally, you'd be better off adding a second, mono amplifier to drive the subwoofer, if you want to keep running the front and rear speakers from the 4-channel amplifier.  However, there are a couple options for running the speakers and sub from a 4-channel amp.

First, you could let the 4-channel amp run the front speakers, connect the rear speakers to the head unit, and bridge the amplifier's rear channel outputs to drive a 4-ohm subwoofer.  This is what I'd recommend, because the rear speakers are relatively unimportant to your overall sound, so it's not much of a sacrifice to run them at the head unit's power level.

Another option is to combine the front and rear speakers to the amplifier's front speaker outputs, and bridge the rear outputs for a sub.  The disadvantage here is that you'll lose the ability to adjust the relative volume of the front and rear speakers--they'll both play at the same level (assuming they're similar speakers) so you won't have the option to make the fronts a bit louder, or vice versa.  You can do this only if you're using 4-ohm speakers in the front and rear locations.

In your truck, I'd consider running new speaker wire from the amplifier to the speakers, because it's relatively easy to run new wiring into the doors of a Silverado.  However, if you want to use the factory wiring, here are the wire colors:

Front left:  (+) tan  (-) gray
Front right  (+) light green (-) dark green
Rear left:   (+) dark brown (-) yellow
Rear right:  (+) dark blue  (-) light blue

Hope this helps!

Brian