It would be crossover wiring sending higher frequencies to tweeter and lower frequencies to the larger speaker.
I couldn't find a wiring diagram showing the Rangers ever had that but 2012 wiring can be scarce.
You can't combine them but your new speaker may have a built-in crossover if it has a tweeter and "woofer" setup then it will have crossover board on the back and you can by pass that to hook 2 wires to the tweeter and 2 to the woofer.
Which 2 go where would be harder to figure out unless it is obvious on the wiring from the old speaker.
You can turn radio on and then hook up 2 wires to a speaker and if it sound high than thats the tweeter hook up making the other pair the woofer.
If you have an OHM meter set it at lowest setting, 100-200ohms then measure old speaker, speakers come in 4ohm, 8ohm, 16ohm, OHM meter won't be super accurate measuring speaker ohms but close enough to find out what you have.
If old speakers are 4ohms and new speakers are 8ohms then it is OK to use the new
If old are 8ohms and new are 4ohms then you could have a problem at high volume, blowing the amp.
Last edited by RonD; 07-22-2015 at 11:08 AM.