Sound device

A sound device comprising:

• a frame;
• a magnet system having a magnetic gap, comprising:
• a yoke fixed to the frame;
• and
• a magnet fixed to the yoke;
• a vibration system mounted on the frame, comprising:
• a diaphragm fixed to the frame;
• and
• a coil fixed to the diaphragm and inserted into the magnetic gap;
• wherein
• the diaphragm comprises a rectangular dome and an edge surrounding the dome;
• the dome comprises two first protrusions opposite to each other and extending along a long axis of the dome, two second protrusions opposite to each other and extending along a short axis of the dome, and four third protrusions enclosed a rectangular shape with the two first protrusions and the two second protrusions;
• two ends of each of the four third protrusions connect with adjacent first protrusion and second protrusions;
• the two first protrusions, the two second protrusions and the four third protrusions are recessed towards the coil along a vibration direction of the diaphragm;
• a concave depth of each of the four third protrusions along the vibration direction is smaller than a concave depth of each of the two first protrusions and a concave depth of each of the two second protrusions along the vibration direction;
• a surface of each of the two first protrusions closest to the magnet along the vibration direction and a surface of each of the two second protrusions closest to the magnet along the vibration direction are both fixed to a surface of the coil facing the diaphragm.