4 Channel Stereo to Mono Output

[sick472]

Sorry for posting this here, but my patience is running out in the electrical section for Truck Audio (it seems a bit slow over there). MODS - you can delete without prejudice should you be so inclined, but it does apply to those of us that contend with the lack of audio space with the fuel tanks in the cab...

Now, I'm nowhere near a stereo guru so be easy on me...I am wanting to make my Sony DSX-GS80 4x100W car stereo drive the 4 speakers, but in mono for each. It also has the RCA connections for a sub which I will be using a compact sub woofer under the seat. I assume the sub woofer will not be affected should I succeed in making the 4 speakers mono.

With the fuel tank behind the seat of my 72 C10, I am limited on space for speakers and decided to build a center console to put 6x9's in. One faces the driver's legs and the other faces the passenger's legs. I will be mounting smaller speakers under the seat facing forward. This is not very conducive to the effects of stereo sound hence making it all mono. I am just wanting decent volume and not an unbalanced sound in the cab.

I have read that a single speaker can be made to produce mono sound by using the "+" of one channel and the "-" of another. This is great for those with the single stock speaker in the center of the dash, but can it be used to turn all the speakers to mono?

If I was not so worried about ruining my new stereo equipment, I would try to...

Use the front left "+" and the front right "-" for the smaller left speaker under the seat and the rear "+" and the rear "-" for the 6x9 on the left side of the console. Vice-Versa for the right speakers.

Any thoughts from those with more stereo knowledge?

Some unfinished eye candy for the photo lovers. I still have to add cup holders, sand and stain...