A speaker comprising: stationary elements (800, 810, 820, 830), such as a back plate, a washer, a magnet and a frame; motional elements (840, 850), such as a surround and a voice coil; and a diaphragm structure (100a, 100b, 100c, 100d, 100e, 200, 300, 60a, 60b, 70) which includes a compressed skins-tensioned core structure, wherein the compressed skins-tensioned core structure comprises: an upper surface layer; a lower surface layer; a core disposed between the upper surface layer and the lower surface layer; an upper transition layer continuous with the upper surface layer at a side, and continuous with the core at another side; and a lower transition layer continuous with the core at a side, and continuous with the lower surface layer at another side; wherein each of the upper surface layer, the lower surface layer, the core, the upper transition layer and the lower transition layer is formed of a substantially homogeneous amorphous material; and wherein each of the upper surface layer and the lower surface layer exhibits an internal compressive stress, the core exhibits an internal tensile stress, and each of the upper transition layer and the lower transition layer exhibits a stress gradient from the internal compressive stress to the internal tensile stress; characterized in that the diaphragm structure (100a, 100b, 100c, 100d, 100e, 200, 300, 60a, 60b, 70) is kept isolated from the stationary elements (800, 810, 820, 830) and only in contact with the motional elements (840, 850) of the speaker. stationary elements (800, 810, 820, 830), such as a back plate, a washer, a magnet and a frame; motional elements (840, 850), such as a surround and a voice coil; and a diaphragm structure (100a, 100b, 100c, 100d, 100e, 200, 300, 60a, 60b, 70) which includes a compressed skins-tensioned core structure, wherein the compressed skins-tensioned core structure comprises: an upper surface layer; a lower surface layer; a core disposed between the upper surface layer and the lower surface layer; an upper transition layer continuous with the upper surface layer at a side, and continuous with the core at another side; and a lower transition layer continuous with the core at a side, and continuous with the lower surface layer at another side; an upper surface layer; a lower surface layer; a core disposed between the upper surface layer and the lower surface layer; an upper transition layer continuous with the upper surface layer at a side, and continuous with the core at another side; and a lower transition layer continuous with the core at a side, and continuous with the lower surface layer at another side; wherein each of the upper surface layer, the lower surface layer, the core, the upper transition layer and the lower transition layer is formed of a substantially homogeneous amorphous material; and wherein each of the upper surface layer and the lower surface layer exhibits an internal compressive stress, the core exhibits an internal tensile stress, and each of the upper transition layer and the lower transition layer exhibits a stress gradient from the internal compressive stress to the internal tensile stress; characterized in that the diaphragm structure (100a, 100b, 100c, 100d, 100e, 200, 300, 60a, 60b, 70) is kept isolated from the stationary elements (800, 810, 820, 830) and only in contact with the motional elements (840, 850) of the speaker.