Abstract: An electro-acoustic device comprising at least one diaphragm including a foil of a piezo-electric polymer material. In the rest condition the diaphragm is maintained in a curved position under mechanical prestress freely mounted by means of a curved chassis and/or an elastic support with a non-flat supporting surface. The diaphragm is given such a curved shape associated with the rest condition and is provided with electrodes so that changes in surface shape in accordance with the electrical signals and the attendant non-linear conversion into acoustic signals by portions of the diaphragm is combined with similar surface changes of other portions of the diaphragm. The conversion into acoustic signals by the other portions amplifying those of the first-mentioned portions for the fundamental frequency of the signals, whereas the other portions and the first-mentioned portions compensate one another for the even harmonics of the signal.