A moving coil loudspeaker has an interchangeable magnet assembly with a plurality of interchangeable magnet segments configured to be circumferentially disposed about a voice coil within the loudspeaker. Heat sink members can be arranged in between the magnet segments to absorb excess heat generated during operation of the loud speaker. In one embodiment, the magnet assembly has at least one annular magnetic member made up of the plurality of magnet segments, a plurality of heat sink members disposed in between the magnet segments, an annular first plate adjacent a first side of the annular magnetic member, and a yoke member having a second plate adjacent a second side of the annular magnetic member and a central cylindrical portion configured to pass through a central opening in the annular magnetic member.