Magnetic circuit and speaker using same

A magnet assembly for forming magnetic fluxes, comprising:

• an outer magnet having a first magnet and a second magnet, the first magnet having a first pole and a second pole, a polarity of the second pole being opposite to that of the first pole, the second magnet having a third pole and a fourth pole, a polarity of the third pole being similar to that of the first pole, a polarity of the third pole being opposite to that of the fourth pole, the second magnet being disposed so that the fourth pole is closer to the second pole than the third pole;
• an inner magnet surrounded by the outer magnet and having a third magnet and a fourth magnet, the third magnet having a fifth pole and a sixth pole, a polarity of the fifth pole being opposite to the second pole, a polarity of the sixth pole being opposite to that of the fifth pole, the fourth magnet having a seventh pole and an eighth pole, a polarity of the seventh pole being opposite to that of the fourth pole, a polarity of the eighth pole being opposite to the seventh pole, the third magnet being disposed so that the sixth pole opposes the eighth pole face to face and the fifth pole is closer to the second pole than the sixth pole;
• a magnetic conductive portion sandwiched between the third and fourth magnets;
• a yoke having a pair of first sidewalls and a pair of projecting portions extending from the pair of first sidewalls for cooperating with the magnetic conductive portion to form a second magnetic gap;
• a first magnetic gap formed between an inner surface of the outer magnet and an outer surface of the inner magnet for generating a magnetic force;
• wherein, the opposite poles of each magnet are arranged in a lateral direction and a width of the magnetic conductive portion is unequal to length of the inner and outer magnets.