Low distortion air motion transformer

Abstract

Air motion transformer (AMT) with a permanent magnet and a rectangular foil arranged in the magnetic field of the permanent magnet, which is folded to form a plurality of folds of identical length, wherein the folds of the foil each have a first conductor section running parallel to the fold lines and adjacent first conductor sections are connected to each other by a second conductor section extending over the fold line, forming a continuous conductor track running meandering on the foil, wherein - the first conductor track sections of at least two adjacent folds have a different mass and - first conductor track sections with higher mass are arranged centrally on the foil and first conductor track sections with lower mass are arranged peripherally on the foil.

Description

[0001] The invention relates to an air motion transformer. In particular, the invention relates to an air motion transformer (AMT) comprising a permanent magnet and a multiply folded film arranged in the magnetic field of the permanent magnet. The folds of the film each have a first conductor track section running parallel to the fold lines, and adjacent first conductor track sections are connected to each other, forming a continuous conductor track running meanderingly on the film, each with a second conductor track section extending beyond the fold line.

[0002] An air motion transformer (AMT), also called a diaphragm or jet tweeter, has—as known, for example, from DE 10 2012 023 822 A1 and WO 99 / 07 183 A1—a foil folded in an accordion-like manner with conductor tracks arranged on it in a meandering pattern. The foil is located in the magnetic field of a permanent magnet, so that when an electrical voltage is applied, the conductor tracks, through which an electric current flows, cause the Lorentz force to open and close the foil folds, drawing in or expelling air. In this way, a very high sound pressure can be generated with a comparatively small membrane movement.

[0003] A disadvantage of the conventional air motion transformers (AMTs), however, is that the typically rectangular base of the foil with identically shaped folds results in a strong fundamental resonance, which can lead to corresponding distortion. This effect manifests itself in the frequency response as a discontinuity that is regularly observed at the transition from the rising edge to the linear frequency range.

[0004] The object of the invention is therefore to create an air motion transformer (AMT) with the lowest possible distortion factor.

[0005] This object is achieved according to the invention by the Air-Motion Transformer (AMT) having the features of claim 1. The subclaims represent advantageous embodiments of the invention.

[0006] The basic idea of ​​the invention is to design the foil of an air motion transformer (AMT) in such a way that the fundamental resonances of adjacent folds differ from one another and, in particular, by a broadband distribution of the fundamental resonances across the entire foil of the air motion transformer (AMT), the corresponding discontinuity in the frequency response is reduced. This is achieved according to the invention by a different conductor track mass arrangement in the folds of the foil of the air motion transformer (AMT), which can be designed symmetrically with respect to the dimensions of the foil. In any case, the impedance curve can be used to demonstrate that the greater the mass differences between the folds of the foil, the more broadly the fundamental resonances are distributed.

[0007] According to the invention, an air motion transformer (AMT) with a permanent magnet and a rectangular foil arranged in the magnetic field of the permanent magnet is proposed, wherein the foil is folded to form a plurality of folds of identical length and wherein the folds of the foil each have a first conductor track section running parallel to the fold lines and adjacent first conductor track sections are connected to one another to form a continuous conductor track running meanderingly on the foil, each with a second conductor track section running over the fold line, wherein the first conductor track sections of at least two adjacent folds have a different mass and first conductor track sections with a higher mass are arranged centrally on the foil and first conductor track sections with a lower mass are arranged peripherally on the foil.

[0008] According to a first preferred embodiment, the Air Motion Transformer (AMT) is designed such that a plurality of the first conductor track sections have a different mass.

[0009] The first conductor track sections are further preferably arranged sequentially, at least in sections, in a direction perpendicular to the fold lines with increasing mass. Particularly preferably, the first conductor track sections are arranged symmetrically with respect to their mass on the film.

[0010] Similar to the mass distribution of the number of first conductor track sections across the entire film, it is further preferably provided that at least one first conductor track section also has an uneven mass distribution over the length of the fold, wherein the mass distribution of the at least one first conductor track section is particularly preferably symmetrical over the length of the fold. Most preferably, the at least one first conductor track section has a lower mass, in particular a lower basis weight, in the middle of its length than at its end sections.

[0011] The invention is described below with reference to the attached Fig. 1 illustrated, particularly preferred embodiments are explained in more detail.

[0012] Fig. 1 shows various conductor track layouts according to a particularly preferred embodiment of the air motion transformer (AMT) according to the invention. In particular, it can be seen that the respective rectangular film has meandering conductor tracks which, in the folded state during operation of the air motion transformer (AMT), cause the opening and closing of the pockets formed by the folds. These conductor tracks are arranged such that, in the folded state, the folds of the film each have a first conductor track section running parallel to the fold lines, and adjacent first conductor track sections are connected to one another to form a continuous conductor track running meanderingly on the film, each with a second conductor track section extending beyond the fold line. According to the invention, the first conductor track sections of at least two adjacent folds have different masses.

[0013] In the Fig. 1A and in Fig. In the layout shown in Figure 1D, it is particularly clear that the first conductor track sections are arranged symmetrically on the foil with respect to their masses, which are evidently different due to the width of the conductor track sections, resulting in an hourglass-like design. It can also be seen that the first conductor track sections have an uneven mass distribution across the length of the fold, which is symmetrically formed, with the first conductor track sections having a lower surface weight in the middle of their length than at their end sections.

Claims

[1] Air-Motion-Transformer (AMT) with a permanent magnet and a rectangular foil arranged in the magnetic field of the permanent magnet, which is folded to form a plurality of folds of identical length, wherein the folds of the foil each have a first conductor track section running parallel to the fold lines and adjacent first conductor track sections are connected to each other to form a continuous conductor track running meandering on the foil, each with a second conductor track section running over the fold line, wherein - the first conductor track sections of at least two adjacent folds have a different mass and - first conductor track sections with higher mass are arranged centrally on the foil and first conductor track sections with lower mass are arranged peripherally on the foil. [2] Air Motion Transformer (AMT) according to claim 1, characterized bythat a majority of the first conductor track sections have a different mass. [3] Air Motion Transformer (AMT) according to one of the preceding claims, characterized by that the first conductor track sections are arranged sequentially at least in sections in a direction perpendicular to the fold lines with increasing mass. [4] Air Motion Transformer (AMT) according to one of the preceding claims, characterized by that the first conductor track sections are arranged symmetrically with regard to their mass on the foil. [5] Air Motion Transformer (AMT) according to one of the preceding claims, characterized by that at least a first conductor track section has an uneven mass distribution over the length of the fold. [6] Air Motion Transformer (AMT) according to claim 5, characterized by that the mass distribution of the at least one first conductor track section is symmetrical over the length of the fold. [7] Air Motion Transformer (AMT) according to one of claims 5 and 6, characterized by that the at least one first conductor track section has a lower mass in the middle of the length of the at least one first conductor track section than at its end sections.

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