Step 3: Drill holes and run your new wires
That meant I only had to drill two holes: one in the top of the left can, and one in the outside of the right can. A #36 drill bit was just right for the 22 gauge wire I used for the speakers.
One mistake I made when drilling the right can (which you can see in the picture) is that when I held the can down the drill bit was perpendicular to the ear-side of the can but at an angle to the surface. This made sticking wires through a little tricky since they had a tendency to get caught up on the inner layers of the plastic.
Next (I did this first, but it doesn't matter), cut two speaker wires for the left speaker (give yourself plenty of extra!) and run it through the headband. This is tricky; you'll need a stiff leader wire of the right diameter to make it through the small gap next to the actual headband wire; I used 1mm stainless steel safety/lock wire.
The trick here to make this easier is to flatten the band out as much as possible; having a friend hold it down while you feed the wire through helps a lot.
Finally, make a loop in your leader wire, loop your speaker wire through it, tighten it down as much as possible with some pliers, and pull the speaker wire through. (again, keeping the headband as flat as possible).
Now you can