Trying to figure out best course to run additional speakers in 2007 Four Winds Class C (with Ford chassis). Would prefer to intercept factory wiring between cab stereo and rear BR speakers that are located over the bed in underside of cabinet. Seeking to mount additional pair in living area, ceiling if possible/practical. Opposing pair of slidouts (sofa/bed and dinnette area) in living area makes running wire thru walls from cab stereo impractical. Suggestions?
The factory connector for the rear speakers is in the driver's B-pillar. I would pull the trim around the cab opening, and run the wiring there to the cabover. Once in the cabover you can fish it through the wall, to the upper corners. Then run the wiring in the upper corner hidden with some 1/4 round trim. That's what I would anyways.
2000 Ford E350 DRW Wagon, V10 - 385,000 miles
2014 CreekSide 31KQBS (QuadSlide bunkhouse)
Be careful intercepting factory wiring and adding speakers to the same circuit.
The impedance of the speakers is usually matched to the output of the stereo. In plain English, the impedance is the resistance of the speakers. They are basically a big resister. If you add more speakers on the same wires, you alter the resistance of the overall circuit and could change the output requirements of the stereo itself. The circuits need to be balanced.
For example, if you have a pair of 8 ohm speakers and you add another pair of 8 ohm speakers, then you are changing the resistive value of the circuit.
Now this is from 30 years ago when I used to mess around with this stuff all the time. Maybe todays standards are different and you can do this. I really don't know as much about these things in todays world, only from yesteryear when I was a puppy......
2007 GMC 3500 dually ext. cab 4X4 LBZ
Duramax / Allison Fire Red
^^^^ x2 ^^^^
With that being said, stereos these days can handle 'overloads' better than back in the day. Personally, no, I wouldn't parallel a 2nd set of speakers along with the stock set, especially since a person almost never knows what the stock speakers impedance values are, whether or not they have crossovers on them, and so on. If you've got 8 ohm speakers in there, and you add another pair of 8 ohm speakers (or worse 4 ohm), you're doubling (or tripling) the load on the output amp of the stereo. Stock units won't put up with it.
Best bet is to get an aftermarket unit, even a cheap one, with more outputs, and even better a set of RCA jack outputs that feed an external amp, and run the new speakers off those.
And wireless is a good option, especially with 12v running everywhere in the first place. Wouldn't take much to put a cheap FM transmitter up front and a 2nd cheap stereo in back tuned to the transmitter's output.