Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electromagnetic
Reexamination Certificate
2000-03-09
2004-09-14
Ni, Suhan (Department: 2643)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Electromagnetic
C381S407000
Reexamination Certificate
active
06792127
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to dome type transducers and particularly to high frequency transducers that have elliptical domes for improved mechano-acoustical strength and performance.
BACKGROUND OF THE INVENTION
For production of higher audio frequencies, loudspeakers have been used in the art. Loudspeakers used to generate higher audio frequencies have conventionally used a dome type loudspeaker. Conventionally, vibrating domes used as the radiating element in loudspeakers have been designed as a truncated hemisphere in section, and to a tubular section at the periphery, as shown in FIG.
1
. The dome and the tubular section may be one part or independent units adapted to connect to one another. The tubular section is connected to a moving electromagnetic coil and the diaphragm and the coil are suspended in an air gap created by pole pieces of a permanent magnet and supplied with an electric current that is representative of the sounds to be reproduced. As a result of the magnetic forces, the radiating dome is moved toward or away from a listener. As the dome moves forward, it compresses the air in front of it and as the dome moves backward it rarefies the air in front of it. The compressions and rarefactions result in the sound produced.
However, at higher frequencies the dome will reach the limits of its motion and result in failure. Using Finite Element Analysis and Laser Vibrometry, the mechano-acoustical design of these prior art domes were shown to exhibit flexure and resonance below 30 kHz, resulting in mechanical breakup and inferior acoustic performance. The resulting breakup occurred at the outer periphery of the dome where the vibration is concentrated in a dome type loudspeaker. As shown in
FIG. 2
, at 22 kHz the prior art dome structures began to show flexing at the periphery of the dome resulting in breakup and inferior acoustic performance. The breakup at the periphery causes the dome and the voice coil to vibrate in a disordered state and thus produce a high “Q” peak in the frequency response curve. As a result of the breakup, the sound radiated from the high frequency diaphragm dome is ragged and unclear due to deterioration of transmissibility of vibration of the voice coil.
SUMMARY OF THE INVENTION
Accordingly, it is general object of the present invention to overcome the disadvantages of the prior art.
In particular, it is an object of the present invention to provide a dome that can operate at higher frequencies.
It is another object of the present invention to provide a dome for high frequency transducers that maintains mechanical strength and acoustical performance at increasing frequencies.
It is yet another object of the present invention to provide a dome for high frequency transducers that maintains mechanical strength and acoustical performance at frequencies above 30 kHz.
It is another object of the present invention to provide a dome for high frequency transducers that has an increased stiffness at the outer periphery thereof.
It is another object of the present invention to provide a dome for high frequency transducers that has an integral skirt extending therefrom to provide for a strengthened outer periphery.
It is still another object of the present invention to provide a dome for high frequency transducers that has a radius at the periphery thereof in order to buttress the outer periphery thereof.
It is another object of the present invention to provide a dome for high frequency transducers that incorporates the voice coil as an element in fortifying the outer periphery thereof.
It is yet another object of the present invention to provide a dome for high frequency transducer that are adapted to function with a variety of magnetic systems used in a variety of loudspeakers.
In keeping with the principles of the present invention, a unique high frequency transducer is presented which overcomes the shortfall of the prior art. It is to be understood that the high frequency transducer is an element that is incorporated into a loudspeaker as is known in the art. The high frequency transducer has a magnet pot with an annular rim extending therefrom. Magnet pot and rim have an inner surface and an outer surface, and a disc shaped magnet is received within said inner surface. A channel is created between an outer circumference of the magnet and the inner surface of the annular rim.
A disc shaped pole is positioned on top of the magnet. An annular lip extends inwardly from the rim and is planar with a pole, however a non-magnetic annular air gap is defined therebetween, thus resulting in an outer pole. The magnet is preferably neodymium iron boron but may be substituted with any other materials having magnet properties substantially similar or superior thereto. An annular holder is positioned on top of and outside the rim and is substantially “L” shaped. The annular holder has at least a cavity extending therein to accommodate a terminal extending therethrough to outside connectors.
An elliptical dome has an annular skirt extending therefrom at an outer periphery in an integral and unitary fashion. The skirt connects with the pole at a side opposing the dome. The elliptical dome is bisected axially and has a major axis extending from a first side of the skirt to a directly opposing side. The dome has a minor axis extending perpendicularly from the major axis to the apex of the dome. The elliptical dome is constructed in accordance with the following general formula for an ellipse: (x
2
/a
2
)+(y
2
/b
2
)=1, and a>b. The dome can be of varying sizes as long as the general formula is adhered to.
The dome and the skirt are constructed of a rigid material in an integral and unitary fashion to provide further strength to the structure at higher frequency ranges. The dome is constructed from a variety of materials such as metals, alloys, metal matrices, and metalloids.
A voice coil, that is preferably cylindrical in section, is wound around and attached directly to the skirt. To further strengthen the structure, the coil is wound as close as possible to the transitional region between the dome and the skirt. An annular surround is attached directly to the dome at a first periphery portion and to a spacer at a second periphery portion thereof, the spacer being in turn attached to the rim.
As constructed, the mechanical strength of the structure is reinforced and the acoustical performance of the high frequency transducer is significantly improved even at frequencies above 30 kHz.
Such stated objects and advantages of the invention are only examples and should not be construed as limiting this invention. These and other objects, features, aspects, and advantages of the invention herein will become more apparent from the following detailed description of the embodiments of the invention when taken in conjunction with the accompanying drawings and the claims that follow.
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Anthony Philip Jeffrey
Wright Julian Roger
KEF Audio (UK) Limited
Myers Dawes Andras & Sherman LLP
Ni Suhan
Sherman Kenneth L.
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