To answer question from Mr. Peyek in article Speaker Types, here I explain how to repair and restore old speaker. Almost old speaker damage at its foam. Foam is a ring foam holds speaker cone from speaker bracket. In main figure, we can see that the speaker damage at speaker foam.

First, unscrew the speaker from the cabinet, marking the color codes of the cables. Then, remove all the foam rests from the basket and also foam on the center of cone.
If there is no dust cover, make sure to avoid crumbs falling into the speaker coil area. You can cover it with glass cap. I used transparent packing tape for protecting the voice coil area. Be sure to remove the tape quickly after, because it might get hard to remove later.

After you remove all foam rest cleanly, remove the packing tape from voice coil gap.
Apply plenty of glue to the edge of the cone. Be sure to apply glue flat enough. Use your finger or the handle of a spoon along the edge. Then put the new foam ring on the cone.

Apply glue to the frame then push the cone down, so the foam ring is pressed into the glue of the frame. Use your finger or the handle of a spoon to press the surround the frame along the edge. You can use a coffee cup or a plate for large speaker diameter, put it on the cone, and then leave it for some hours, or simply the next evening..
In this step, a shim has to be closed in the voice coil, in order to align the voice coil center. If the shim is not centered correctly, it will produce noise later. I am using paper as shims here, but plastic is much better, it is more flexible and easy to center it.

When the glue of the shim had become dry, I assembled the speaker to the cabinets. Ok, I connected and listened it. They sounded good. But I did not know how they sounded before. I really cannot say the sound as same as before. But I am sure it would never been better than factory assembling.