Moving-coil loudspeaker

A moving-coil loudspeaker comprising:

• a front cover, a vibration system, and a magnetic circuit system arranged one on top of the other;
• the front cover including a third conductive material layer;
• the vibration system including a diaphragm, a spider, and a voice coil combined one on top of the other, the diaphragm comprising a diaphragm body part with a surround portion and a diaphragm reinforcing part combined with the diaphragm body part at a lower central location of the diaphragm body part;
• and
• the magnetic circuit system including a center washer, a center magnet, and a magnetic yoke combined one on top of the other;
• wherein the diaphragm reinforcing part comprises a first conductive material layer, the spider comprises a second conductive material layer, and the diaphragm reinforcing part and the spider are bonded by an insulative adhesive;
• and
• wherein the first and second conductive material layers functioning as a movable plate, and the third conductive material layer functioning as a fixed plate constitute a capacitor structure for detecting a vibration displacement of the moving-coil loudspeaker.