The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 29, 1998
Filed:
Apr. 17, 1997
Lars Goller, Herning, DK;
Scan-Speak A/S, Videbaek, DK;
Abstract
The invention is a loudspeaker. The loudspeaker includes a driver diaphragm having a voice coil and an associated magnet system including an annular air gap within which the voice coil locates, the voice coil being longer than the axial extension of the annular air gap, the magnet system including a central pole piece, the voice coil and central pole piece having a frontal end towards said driver diaphragm and a rearward end away from said driver diaphragm, the magnet system further comprising a cylinder arrangement, of a material and of a wall thickness sufficient to provide a conductivity suitable to act as a short circuit ring carrying compensating induction currents, the cylinder arrangement comprising a root part at a root area of the pole piece and an inner pole ring part rearward of the annular gap, the root part being located outside the rearward end of the voice coil when the voice card assumes a position of rest, and further comprising an outer pole ring part located forward of the annular gap, the inner pole ring part and the outer pole ring part both being shorter than half a length of the voice coil.