Shaker500 Middle Wire harness?

[warrior86]

what is the middle wire harness for on the shaker500?

reason i ask is because i tried wiring up my aftermarket pioneer single din to the harnesses I bought and then plugging them into the car and everyone says just need 2 harnesses. Either way the pioneer didnt work but i dont think it was related because the harness's. The reason is because I tried another cd player and that at least powered on!

So yea, just wondering what the middle one is for?

 

[warrior86]

also.....

When I had my subs plugged into my pioneer unit in my old car, I could control the output of the subs seperately through the head unit. If I have the subs that are in the doors connect AS Well, will there be 2 places in my my head unit, like... input 1 settings and then input 2 settings???