Abstract: The invention relates to a permanent magnet system with associated coil arrangement, the permanent magnet system consisting of two axially polarized permanent magnet rings which are mounted one behind another in the axial direction, like poles of the permanent magnet rings being opposite one another, the two permanent magnet rings being distanced from one another by a soft magnetic spacing washer, the permanent magnet rings being surrounded on the outside by a coil in such a way that the coil central axis coincides with the central axis of the permanent magnet rings, the center of the coil being located in the normal position of the coil at the level of the soft magnetic spacing washer, at least one coil being located inside the inside diameter of the permanent magnet ring in such a way that the coil central axis of the coils coincides with the central axis of the permanent magnet rings, the center of the coils being located in the normal position of the coils at the level of the soft magnetic spacing washer.

Abstract: The present invention relates to a loudspeaker diaphragm which is provided with a rear load and the vibration characteristic of which is improved in that the work to be performed for compressing the air behind the loudspeaker diaphragm is reduced. For this purpose, the loudspeaker diaphragm is provided with openings so that the air located behind the loudspeaker diaphragm can escape. At the same time, the introduction of the openings causes a decoupling of the vibrating diaphragm parts with respect to the frequency response when the loudspeaker diaphragm and the openings are suitably dimensioned, so that it is predominantly the inner part of the loudspeaker diaphragm which vibrates in the case of high notes, while the entire loudspeaker diaphragm vibrates in the case of low notes.

Abstract: A loudspeaker is disclosed with a diaphragm and an annular moving coil fastened to the diaphragm. An annular permanent-magnet system is arranged concentrically relative to the moving coil and is fastened to a support. To obtain a high-power and extremely slim system, the moving coil surrounds the permanent-magnet system with only a small air gap and, on its outer surface, carries a thin-walled annular core of amorphous metal. The permanent-magnet system consists of two permanent-magnet rings spaced from one another by means of a soft-mangetic annular intermediate disc and having like poles facing one another.

Abstract: An acceleration pickup or detector which is provided with a cable outlet located at right angles to a direction of the main vibrations to be detected, especially for detecting knocking signals in internal combustion engines. Connecting elements linking leads of the connecting cable with the acceleration pickup are disposed on a side of the acceleration pickup opposite to the axis of symmetry with respect to the cable outlet. An additional mass is provided on the side of the connecting elements, which mass forms a common counter mass with the connecting elements for the connecting cable.