Step 1: What you'll need
As the speakers didn't had any problems, I didn't have to do nothing.
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.
As it was hard to keep the wire in the right place, I made a tool with some hard wire.
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.