i am just about to do my first installation ever and i have alpine type-r 6x9 speakers for the rear deck. could anyone tell me which of the two tabs is the negative and which is the positive? one tab is bigger than the other.

in theory it does not matter as long as both speakers correspond.

thats what i thought but then someone said they will cancel out and get no sound. anyone know the proper thing to do?

make the larger one positive

Yes.

That'* why you asked me which was which....

Pay attention to which tab each wire came off and do the 9v battery test. Take a 9v battery and touch the posts on the tabs. If the speaker jumps up, you have the polarities correct. Pos is pos and neg is neg. If it pulls into the cage, there backwards. Its that easy. you can now figure out which wire is pos.