Reflex Volume Calculator Conversion THD dB / percent Level lowerance Membranesurface and girth Absorption circuit and trap circuit for inductors Absorption circuit and trap circuit for capacitors Transmissinonsline calculation "Intertechnik line" Wood Membranesurface und girth It is often necessary to know the diaphragm surface or the scope to calculate the Thiele/Small- parameters or to forecast sound focusing. After entering the speaker diameter the output values are in mm. Diameter mm