First things first: pull the foam out of the hearing protection. That was easy!
Next, disassemble the headphones. Mine had small phillips screws holding the band together, and tri-wing screws holding the phones together. Why did this company think that it was important to keep people from opening the headphones they bought, I don't know. A security-head screwdriver bit set like this one
or this one
is a useful thing to have on hand anyway. (If you don't have a set and are itching to open your headphones, you could just use a rotary tool to grind through the three screw posts.)
Make a note (or photo) of which wires go to what.
Finally, use an exacto knife to cut through the glue that's holding the speakers to the grill, and use a small flat-head screwdriver to pry the speakers off. Go slow!