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Ceramic metal matrix diaphragm for loudspeakers
| Details |
Inventors: Devantier, Allan O.; Nguyen, An D.;
Assignee: Harman International Industries Incorporated (Northridge, CA)
Primary Examiner: Tran; Sinh
Assistant Examiner: Dabney; T.
Attorney, Agent or Firm: Squire, Sanders & Dempsey
A speaker diaphragm for a loudspeaker that has a composite material formed of two layers of ceramic material separated by a light metal substrate with the percentage ratio of the thickness of the ceramic layers to the light metal substrate being in the range of from about 10% to 45% for each ceramic layer and a corresponding 80% to 10% for the lightweight metal substrate. |
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DETAILED DESCRIPTION Thus, the present invention relates to a material that is formed of a matrix, or layers, of a light metal such as aluminum, sandwiched between two ceramic layers, preferably aluminum oxide (Al.
sub.
2 O.
sub.
3).
The material is particularly useful as a loudspeaker diaphragm.
The ceramics, Al.
sub.
2 O.
sub.
3, are generally stiffer than metals and also offer improved damping.
A loudspeaker diaphragm made of aluminum oxide would offer performance superior to any of the known materials today.
Unfortunately, ceramics are also very brittle, and a diaphragm made of pure aluminum oxide would "shatter itself to bits" under normal loudspeaker operations.
Thus, the material of the present invention is made of two layers of ceramic separated by a light metal substrate.
Of the common metals, aluminum has the lowest density, making it the ideal substrate.
However, there is no known reason why other metals, such as copper, titanium, and the like should not have the same advantages as the use of aluminum.
A skin of alumina, or ceramic, is formed by well-known means, such as anodizing and/or being "grown", on each side of the aluminum core or substrate.
Anodizing provides a molecular bond instead of a chemical bond between the substrate and the ceramic material.
The alumina thus supplies the strength and the aluminum substrate supplies the resistance to shattering.
It has high internal frequency losses.
The resulting composite material is less dense and less brittle than traditional ceramics, yet is significantly stiffer, and has better damping than titanium.
It also resists moisture and sunlight better than any polymer and is at least as good as other metals for providing such resistance.
Thus, it is an object of the present invention to provide a loudspeaker diaphragm formed of composite material.
It is also an object of the present invention to provide a loudspeaker diaphragm composite material that is less dense and less brittle than traditional ceramics, yet it is significantly stiffer and has better damping than titanium
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Audio Signal Processing 
