Aurum Cantus AST30130-RD replacement diaphragm for AST30130 Aero Striction Tweeter. Aurum Cantus AST (Aero Striction Tweeter) pneumatic transducers utilize a special flexible low-mass aluminum diaphragm that is carefully folded and then suspended in a highly saturated magnetic field. Source sounds are reproduced by the compression/expansion action of the diaphragm, resulting in incredibly instantaneous, accurate response.