Abstract: A structure of an acoustic diaphragm adapted to be used in a planar diaphragm speaker is provided. The structure includes a bottom carbon fiber layer and a top carbon fiber disposed on the bottom carbon fiber layer, wherein the fibers of the top carbon fiber layer and the fibers of the bottom fiber layer are parallel with each other.

Abstract: An invisible speaker applied in an electric equipment is disclosed. The invisible speaker includes a transparent device disposed on a body of the electric equipment and having a transparent portion for a vision face of the electric equipment, wherein the transparent device is a distributed acoustic radiator for sending out a sound, and a first transducer connected to the transparent device for vibrating the transparent device to send out the sound.

Abstract: A method for producing a carbon fiber composite layer having high strength is provided. The method includes steps of providing two carbon fibers layers having fibers in parallel with each other and disposed in a stacked form, and heating and pressing said two carbon layers simultaneously to form said carbon fiber composite layer. A structure of an acoustic diaphragm adapted to be used in a planar diaphragm speaker is also provided. The structure includes a bottom carbon fiber layer and a top carbon fiber layer disposed on the bottom carbon fiber layer, wherein the fibers of the top carbon fiber layer and the fibers of the bottom carbon fiber layer are parallel with each other.