Pretty easy if you can solder reasonably well. It get's harder if you chose a difficult wire to work with. I bought a Rat Shack 1/8 inch stereo to 1/8 inch stereo cable, cut one end off, opened up the phones and soldered it in, put them back together and was done in about half an hour. Basic hand tools and a soldering iron were all I needed. Mine are MDR-7506's but they are identical as far as I can tell from pictures.