Polarity?
 

hey i got the colour codes for the wires but the diagram i have doesn't say the polarity of the wires.. i think i got some of the wires backwards cause i have no bass,

you are correct, you have no bass because they are out of phase and cancelling each other out...

i'm pretty sure the polarities have been posted before, try a search.

what would happen if you got em mixed up?

just that, you lose bass and stereo imaging, as well as gain phase shifting.

the times when using this to an advantage is for front to rear tuning, not left to right, or with shifting the subwoofers 180deg. out of phase.