A diaphragm includes a diaphragm matrix and at least one reinforcing structure composited with the diaphragm matrix. The at least one reinforcing structure includes at least one freestanding carbon nanotube structure. A loudspeaker includes a magnetic circuit defining a magnetic gap; a bobbin located in the magnetic gap; a voice coil wound on the bobbin; and a diaphragm. The diaphragm includes an inner rim fixed to the bobbin a diaphragm matrix, and at least one reinforcing structure composited with the diaphragm matrix. The at least one reinforcing structure includes at least one freestanding carbon nanotube structure.