# US 6,724,909 B2 · Speaker apparatus

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- Number: US 6,724,909 B2
- Document ID: US6724909B2
- Status: Granted
- Kind: B2
- Application number: 09/986,668
- Filed: 2001-11-09
- Published: 2002-05-16
- Granted: 2004-04-20
- Earliest claimed: 2000-11-10
- Assignees: Fujitsu Ten Limited; Timedomain Corporation
- Inventors: Katsuhiko Tsumori; Akira Nishikawa; Hiroshi Kowaki; Hiroyuki Yoshii
- Web page: https://patentgrep.com/patent/US6724909B2

## CPC

- H04R 9/06: Loudspeakers
- H04R 9/025: {Magnetic circuit}
- H04R 2209/027: Electrical or mechanical reduction of yoke vibration
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

A weight is attached to the rear side of a magnetic circuit of a speaker unit. The tip of a boss that projects to the front side from the weight is joined to the rear side of a center pole of the magnetic circuit with a bolt. Even if reactive force that is generated when an electrical signal is converted into mechanical vibration by the magnetic circuit and a voice coil and sound waves are emitted from a vibration plate is transmitted to the magnetic circuit, the vibration of the magnetic circuit is suppressed by the weight. In this manner, sound quality with a good transient characteristic can be obtained.

## Claims

### Claim 1

A speaker apparatus comprising:
a speaker unit including a converter, having a magnetic circuit, for converting an electrical signal into mechanical vibration along an axial line direction of a voice coil, a vibration plate for emitting sound waves to a front side of the converter, and a frame fixed to the converter, for vibratably supporting the vibration plate from a rear side thereof; and
a weight heavier than the speaker unit, having a boss formed so as to project to a front side from a central portion of the weight along the axial line of the voice coil, a cross section of the boss taken perpendicularly to the axial line being smaller than that of the magnetic circuit, a tip of the boss being fixed to a rear side of the magnetic circuit.

### Claim 2 (depends on 1)

The speaker apparatus of claim 1, wherein the magnetic circuit is of an external magnet type and has an annular cancellation permanent magnet for decreasing leakage magnetic flux on a rear side of an annular main permanent magnet for generating magnetic flux for driving the voice coil, and wherein the boss of the weight penetrates through a hollow portion of the cancellation permanent magnet and is fixed to a rear side of a center pole of the magnetic circuit.