A speaker includes a vibration system including a vibrating diaphragm and a flat voice coil for driving the vibrating diaphragm; a magnetic circuit system including a first magnet group, a second magnet group and a third magnet group, lined up in turn along the vibration direction of the vibration system; and a housing for accommodating the vibrational system and the magnetic circuit system. The first magnet group includes a first magnet and the second magnet with opposite magnetic poles thereof faced each other. The second magnet group includes a third magnet and a fourth magnet with N-pole of the third magnet close to S-pole of the fourth magnet. The third magnet group includes a fifth magnet and a sixth magnet with opposite magnetic poles thereof faced each other.