Step 1: What you'll need
A broken headphone (the cheap ones), soldering iron, pliers, knife, screwdriver, tape, wide scotch tape, thin scotch tape, glue (a strong one and a normal one - as you can see, I do not have the normal one...) and a ruler (that I also don't have, so I used what I do have).
Take it apart carefully. Look for broken things or a loose wire. Here everything is ok, but usually this is where the fault lies.
As the speakers didn't had any problems, I didn't have to do nothing.
Start breaking with the pliers untill there's just the slot. (This is what will protect the phones).
Before you break it, remove the foam carefully ( Yeah, i forgot to take a pic for that...).
Then, you measure the slot and adapt the image to it's size.
The volume control had a loose wire, so i fixed. (Its really easy. There are markers to every wire, the hard part was soldering without really knowing how).
As it was hard to keep the wire in the right place, I made a tool with some hard wire.
Now, you'll glue the foam onto the slot and on the foam. Use the strong one. Let it dry for about 10 minutes. It can take more or less time to dry, depending on how much you used.
Use some internet image as reference and make your pattern. You can use this one or any of your choice, as long as you like it.
Cut the shapes and make a small cut in the middle of the black circle with the knife blade. Then remove the black circle leaving a small black outline.
With a ruler (a normal one, that you have and I do not...) fold the cubes. Do it on both sides.
When the glue is completely dry paste the foam and try to center both. Cut the excess foam leaving a small border. Put some glue in the border.