What you will need is:
A pair of old/new speakers preferably with damaged dust caps
A pair of scissors
A sharp blade of your choice
Some old drinks cans uncrushed
Some glue of choice
A weight ( d cell battery or similar by weight)
And some steady hands that are patient
Step 1: Remove Old Centre Cap
Sorry don't have any in the making at the moment so you will just have to imagine the speaker with the centre cap removed
Step 2: Get Yourself a Couple of Drinks Cans
Step 3: In This Step All You Will Need Is Glue
I have added another few photos of a 2" speaker with the centre caps fitted the normal (convex) type way round they work ether way round and I think I will be fitting them in to the logs at the side of my tv?
Step 4: Tidy Up and Enjoy
Try not to get glue all over the cone like I did it won't affect the sound but it doesn't look professional.
Also try your very hardest not to let glue enter the coil gap or you can say goodbye to your defunct speaker as that woul be quite difficult to remove!
Iv managed in all the speakers I have don not to do this so it is safe enuf to do most speakers have a small lip from the coil to the cone just don't spill any down the hole!
Happy modifying the centres are very easy to polish before glueing in to place to give the look of expensive speakers.
Also most cans have a number stamped on the base this just gives the speaker a unique number once polished it's not visible so don't worry about it too much.