Abstract: The membrane of a loudspeaker, which is driven on a limited part of the membrane, does not move completely like the tone current. For example, a cone, which is driven in the top, provides more accurate driving by also being driven in the periphery from the drive system back where the movement of the sound coil also is taken out. The driving can e.g. be distributed with a cone of net. With separate sound coils from the front side and back side of the driving system, the loudspeaker properties can be optimised. The biggest benefit is achieved with a long loudspeaker where the movement is taken out from the back side of the long drive system and distributed with plates, cones and wavy walls to a bulgy membrane edges.

Abstract: A long and narrow loudspeaker on an entire wall gives off a cylindrical wave, which covers the entire room. Extra loudspeakers fixed at an angle against the wall will be heard in another direction, producing angle stereo independent of where one is in the room. Electro-dynamic loudspeakers are made of long plates of iron with air gapes between them where magnetic fields are produced. In the air gaps are strips, which conduct the sound currents. The strips influence directly one or more membranes. The magnetic field can be produced by permanent magnets, electromagnets or through concentration of geomagnetic fields. Long loudspeakers, which use other forces such as electrostatic forces, only need to be made for small sound pressure at the membrane.

Abstract: A long and narrow loudspeaker on an entire wall gives off a cylindrical wave, which covers the entire room. Extra loudspeakers fixed at an angle against the wall will be heard in another direction, producing angle stereo independent of where one is in the room. Electro-dynamic loudspeakers are made of long plates of iron with air gapes between them where magnetic fields are produced. In the air gaps are strips, which conduct the sound currents. The strips influence directly one or more membranes. The magnetic field can be produced by permanent magnets, electromagnets or through concentration of geomagnetic fields. Long loudspeakers, which use other forces such as electrostatic forces, only need to be made for small sound pressure at the membrane.

Abstract: A transformer or inductor core of magnetic material has three legs (6, 8, 10) interconnected by yokes. The core comprises loops (12, 14, 16) of wires and/or strips of magnetic material, wherein each of the loops makes up part of two of the legs. Loops making up part of two different leg portions are interleaved in a common leg portion. This provides for mechanical stability and good magnetic properties for the core.

Abstract: A transformer core comprises at least one leg and at least one yoke part, wherein the cross section of the leg or the legs regularly multi-edged with more than four edges. The core is made up of rings rolled from strips of constant width, whereby good electrical properties are achieved. The transformer is also easy to manufacture and avoids waste of material.

Abstract: A transformer or inductor core of magnetic material has three legs (6, 8, 10) interconnected by yokes. The core comprises loops (12, 14, 16) of wires and/or strips of magnetic material, wherein each of the loops makes up part of two of the legs. Loops making up part of two different leg portions are interleaved in a common leg portion. This provides for mechanical stability and good magnetic properties for the core.