There is provided a speaker or a speaker system which has no chance of disabled ventilating air in a space enclosed with a voice coil bobbin to outside of the magnetic circuit through a throughhole C formed in a magnetic circuit to communicate with the space enclosed with a voice coil bobbin, even if mounting a speaker between inner surfaces of a casing, because of enabled ventilating air from a space enclosed with a voice coil bobbin to outside of a magnetic circuit through an air path 3c formed in the magnetic circuit to communicate with the throughhole C.