Patent ID: 7953240

Claim:
A loudspeaker apparatus comprising: a housing having an opening formed therein; an adsorptive material disposed inside the housing, and for physically adsorbing gas inside the housing; a vibration section including a diaphragm and a diaphragm support member for supporting the diaphragm, the vibration section being disposed in the opening formed in the housing, the diaphragm support member having a stiffness; a drive section for driving the diaphragm to generate sound from the diaphragm; and a negative stiffness generating mechanism disposed inside the housing, the negative stiffness mechanism for generating a negative stiffness and for reducing an acoustic stiffness inside the housing, the acoustic stiffness acting on the diaphragm, wherein a stiffness acting on the diaphragm is determined based on the acoustic stiffness, the stiffness of the diaphragm support member, an amount by which the acoustic stiffness is reduced due to the adsorptive material, and the negative stiffness generated by the negative stiffness generating mechanism, and wherein the negative stiffness generated by the negative stiffness generating mechanism is less than a value resulting from subtracting, from the sum of the acoustic stiffness and the stiffness of the diaphragm support member, the amount by which the acoustic stiffness is reduced due to the adsorptive material, wherein the drive section includes: a first magnetic circuit disposed inside the housing and having a first magnet closer to the diaphragm; and a second magnetic circuit having a second magnet disposed facing the first magnet via the diaphragm and a gap formed in a vibration direction of the diaphragm, wherein a predetermined magnetic gap being formed in at least one of the first and second magnetic circuits, the vibration section further includes: a voice coil disposed in the magnetic gap; a voice coil bobbin fixedly disposed on the diaphragm, and for disposing the voice coil in the magnetic gap and supporting the voice coil; and a non-magnet member, which is a magnetic material, and which does not include a magnet, and is disposed in at least a portion of the diaphragm provided in the gap, the negative stiffness generating mechanism includes: the non-magnet member; the first magnetic circuit; and the second magnetic circuit, a balanced position in the gap of the non-magnet member being a reference with respect to a vibration direction of the diaphragm, and the negative stiffness generating mechanism applies repelling force in the vibration direction to the non-magnet member in a direction which allows the non-magnet member to move away from the balanced position, thereby reducing the acoustic stiffness inside the housing.