Diaphragm with partitions for rectangle slim speaker

A diaphragm with partitions for rectangle slim speaker is provided to suppress internal deformation due to heat generated from a coil by using a structure of the partitions thereof. A diaphragm(20) has a rectangular shape and is coupled with a voice coil former(10). The diaphragm includes partitions(21). The partitions are inserted into an internal space(11) of the voice coil former. A prominent rim(27) is formed on a backside of the diaphragm. The partitions are inserted into the inside of the prominent rim. A projection is formed at a lower end of the partition. The voice coil former is coupled with the projection when the partitions are inserted into the internal space of the voice coil former.