Audio Systems: Is a car stereo head unit bridgable?, stereo head unit, bridging an amp

Question
Basically, I'm running a Panasonic CQ-C1333U, car stereo head
unit, no amp, and powering (2) 5.25 dash speakers and (1) 6x9
in a box, between the front seats of a mini van. Since I'm only
running (1) 6x9, I have one un-used rear channel, can I bridge
that into the 6x9 I have connected, to get double power. If so,
how? I've heard the term bridging an amp before, but have never
done it.  Can I just connect both (-) wires together at the head,
then connect both (+) wires together, and connect my one 6x9
to that to get double power, or is this a crazy damaging idea?  I
appreciate your time. Thanks! - Brad

Answer
No sorry, it will not work at all that way. It wont damage anything, it just wont work, if you connect to both posatives you'll get practially nothing (much less sound) if you connect to both negs you get absolutly nothing and if you use a pos from one and a neg from the other you'll get the same thing as just using one channel.  If you connect the posatives and negatives of both channels together and put the speaker on that (this could damage the unit and is not how bridging works but) theoreticaly you could get more current this way but not more volatage and higher voltage is what you need and what real bridging does. I'd be happy to explain the technical reasons why if you're interested, let me know.  the best thing you can do to make use of that other channel is get another speaker.  make sure it's the same exact make and model and it's in the same size box or it will sound terrible playing with the other one.
Good luck and please let me know what you do.