Alright sir. But before we go forward, we need to be sure you have the same tweeter. I know they are the same on the C6 and the C8. I assume they are in the C2 and C4 but I don't know that for sure. You may want to research this and be sure that your C4 uses the same 5DR53063 tweeter that my C6 does.
You could just pull your broken one out and see if it is stamped on the side. If you haven't done so be fore, here is the procedure (assuming it is the same as my C6): You will need to first pull the upper woofer. To do so, remove the ring that covers the screws, then the screws holding in the woofer. Once the woofer is out, then reach up inside and you can turn the tweeters clockwise and this will unlock them and you can pull them out of the woofer hole.
Lets hope yours matches mine and the hunt is over. It took me years to get mine.