Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having electrostatic element
Patent
1995-01-09
1997-02-11
Kuntz, Curtis
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Having electrostatic element
381186, 381197, H04R 2500
Patent
active
056029306
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a loudspeaker incorporating an inductively coupled tweeter particularly, but not necessarily only, for use in an automotive audio system.
Background op the Invention
A loudspeaker conventionally comprises a magnet assembly with an annular gap having a radial magnetic field within the gap. A voice coil is suspended in the magnetic field by means which permit it to be moved axially without touching the sides of the magnet assembly. The voice coil is wound on a rigid tube that is connected to a diaphragm, the outer edge of which is flexibly supported by a frame that is itself securely attached to a part of the magnet assembly. However, with this type of loudspeaker the frequency range of the sound produced is limited to low and medium frequency and, in order to reproduce high frequency sounds, it is proposed to incorporate an inductively coupled tweeter.
Inductively coupled tweeters in loudspeakers are known. For example, GB 545712 discloses an inductively coupled conductor in the form of a radiating dome positioned in the magnetic gap inside the main voice coil of a loudspeaker. The low and medium frequency sounds are radiated by a conventional cone, the high frequency sound is produced by he dome and is directionally controlled by a special horn fixed to the centre pole.
In U.K. Patent No. 2118398 a similar arrangement is disclosed where a radiating dome is positioned over he central pole and supported by an annular suspension means. The dome is positioned within he tube or former supporting he voice coil and receives is energizing signals inductively from he voice coil. The dome is horn loaded by the same diaphragm as the voice coil, reproduces high frequency sound.
More recent proposals are contained in European Published Applications 0344974 and 0344975. European Publication 0344974 is an improvement on the loudspeaker disclosed in GB Patent No. 2118398 and includes a fixed element providing phase correction, which is supported by he pole through a hole in he dome. The radiating dome is supported by an annular flexible suspension on the pole face and also by another smaller flexible suspension on the underside of the phase correcting device. This provides two mall sealed chambers. On the free end of the former there is a flared extension which is designed to provide a smooth acoustic impedence transition.
European Publication No. 0344975 discloses a similar electro acoustic transducer as disclosed in GB Patent No. 2188398 but is directed to the provision of an electrically insulating layer between the dome and the centre pole. This allows the annular gap to be of a minimum clearance whilst eliminating short circuiting between the pole and the dome.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved loudspeaker with an inductively coupled tweeter.
According to the present invention, there is provided a loudspeaker comprising a pole, a surrounding magnet defining an annular gap with the pole, a tubular former, a voice coil carried by the former and disposed within the annular gap, and a conductive skirted dome supported on the pole upon an insulated support with the skirt disposed in the annular gap so as to be inductively coupled with the voice coil when the voice coil is energized, characterized in that the insulated support provides a plurality of spaced positions of support.
Preferably, the dome is supported upon three arcuate points of support. The three points of support may be provided by a gasket shaped to provide the arcuate points of support. The conductive dome suitably includes a central opening with a clearance to receive a phase plug attached to the pole by a stem passing through the opening. The underside of the phase plug may include a second gasket around its central supporting peg, to which the dome may or may not be bonded, to limit travel of the dome and to ensure that the skirt is always located in the annular magnetic gap. The reduction of support for the dome by using a pole face gasket having
REFERENCES:
patent: 4965839 (1990-10-01), Elieli
Harman-Motive Limited
Kuntz Curtis
Le Huyen D.
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