i had a set of marshmallows with a broken cable so i gave this a try. for me, it was harder than this guy made it look to open up the marshmallow earbuds & expose the wires. in the end i managed to make it work and it did for a few months before they failed probably because i had soldered it badly. in trying to fix it i believe i made it worse, and so gave up and bought a new set of marshmallows, and when the cable finally goes kaput i'll try this hack again
www.youtube.com/watch?v=yLzs5aHv3jI