Music speaker devices come in all shapes and sizes. Some of them are small and designed to fit in your pocket, while others are large and meant to be placed on a table or desk. They can be powered by batteries or plugs into an electrical outlet. Most music speaker devices have two speakers: one that faces forward and one that faces backward. This allows the device to project the sound in all directions. However, some devices have just one speaker, which means the sound is directed straight out of the device.