Desolder the four speaker wires connecting the speaker to the motherboard using a soldering station.

If you're unfamiliar with soldering or desoldering check out this guide How To Solder and Desolder Connections

Be sure to wear protective eye wear. Also, keep in mind that the soldering iron will become extremely hot.

The tool in the picture is not required for this step. It is just being used to point out the wires.