A speaker comprises at least four diaphragms, inner connecting rods, outer connecting rods, and a cavity sealing housing. Diaphragms spaced apart from each other respectively form a set of diaphragms. The two sets of diaphragms move relative to each other. Connecting points are provided on rigid domes of each of the diaphragms. The inner connecting rods are connected to the diaphragms via the connecting points on the domes. The inner connecting rods respectively connected to the two sets of diaphragms are connected one to another via different outer connecting rods. Cavities of the speaker are formed between adjacent diaphragms. Cavities spaced apart from each other jointly form a front acoustic cavity. The cavities adjacent to the front acoustic cavity form a rear acoustic cavity. The cavity sealing housing seals the front acoustic cavity/rear acoustic cavity, thus allowing separation of the front and rear acoustic cavities of the speaker.