Rear Deck Shaker Speakers

Well I have seen all the posts about changing speakers and such and I went out to my car, cralwed in the trunk and took a look at the rear deck speakers. They are screwed in and then there is a harness there. No aftermarket speaker will have the male end of that harness installed on it, it will have + and - leads. How do you only change the speakers without chaning the head unit etc? I saw there were two silver wires connected to this harness of some sort I assume that it was the + and - of the speakers connected to the male end of the harness? Can anybody give me some insight. Thanks in advance!