"Why is one of the speakers working?"에 답변My daughter had the same problem. Only one speaker working. It turned out that the connector cable (the cable with the TRRS plugs on both sides; which transmits the signals from the audio source to the headphones) had a broken wire. I found out by checking the conductivity of the cables with an ohmmeter, probing sequentially the corresponding segments of the TRRS connectors (if you don't know what a TRRS connector is, check on Wikipedia under "phone connector (audio)"). The cable is very flexible and is coated with a very soft rubber-like plastic. It invites rolling up the cable to a tight coil, or playing with it and bending it strongly while listening to music. This is how one of the wires may have broken. So, before you dissassemble the headphones (and possibly damage them in the process), first check the cable leading to the headphones.