An electrical signal transmission device such as a delay line or filter of the acoustic, reflection mode type wherein an input electrical signal is converted to acoustic energy propagating along a medium such as a thin rectangular strip of spring steel toward a mismatching structure such as an array of gratings which reflects a portion of the energy for further propagation and conversion to an output electrical signal. The phase response of the device is shaped or compensated by a region of phase affecting material, such as a thin mass-loading film of gold or similar material, located on the propagating medium in the path of the reflected signal. A pattern or profile generated from the measured phase response of the device is used to control application of the material, preferably by vapor deposition, the profile and thickness of the region or film being predetermined to shape the phase response without affecting the amplitude response.