Acoustics – Diaphragm – Particular shape
Patent
1994-05-25
1998-02-03
Dang, Khanh
Acoustics
Diaphragm
Particular shape
181174, 181166, 181171, 381203, G10K 1300
Patent
active
057147221
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a loudspeaker.
BACKGROUND OF THE INVENTION
It is common for the diaphragm of loudspeaker element to consist, for example, of a stiff cardboard cone. An outer edge of the diaphragm is flexibly attached to a framework of the element. A voice coil, moving in a magnetic field, is fixed in the center of the cone. Currently, the conical diaphragm is frequently manufactured of plastic, fiber or even aluminum. The suspension of the cone is realized by corrugations on its external edge or a rubber molding glued to that edge and by a flexible support, or `spider` attached to the voice coil. A conical loudspeaker can produce distortion caused by buckling strains arising in the diaphragm and by pressure foci.
There are also designs that employ a planar diaphragm attached to the edge of the loudspeaker casing. Such a design is presented in U.S. Pat. No. 3,509,290. The planar diaphragm is manufactured of expanded polystyrene or some other comparable plastic material. The diaphragm then has a number of controllers connected with it, each for its own frequency range. The controller in the center of the diaphragm typically produces the bass frequencies and one, at the edge, the higher frequencies. The disadvantage of this design is that several controllers have to be used for different sound frequency ranges. Also, with this design, a distribution filter must be used to divide the incoming signal between the controllers. The use of a number of controllers with one diaphragm causes mixing between them. The missing is manifested in distortion.
U.S. Pat. No. 3,586,121 shows a loudspeaker diaphragm that is thinner at the center than in the surrounding areas. This diaphragm has a front surface that is essentially of the form of a truncated cone. The controller is attached to the central area of the diaphragm. The diaphragm is manufactured of a foamed plastic such as polystyrene and is typically 2-3 mm thick at the center and varies in the range 3-7 mm in the surrounding areas. The purpose of the attenuated concave area on the front surface is to improve the poor sound reproduction at high frequencies known to be experienced with planar diaphragms made of a foamed plastic. The drawback with this loudspeaker is that the truncated cone of the front surface behaves essentially in the same manner as a conical loudspeaker.
U.S. Pat. No. 1,863,072 discloses a loudspeaker diaphragm that possesses a circular center part and a first annular part, which is joined to the edge of the circular part. A second annular part is joined to the outer edge of the first annular part. The second annular part is fixed to the casing by its outer edge. The three parts are made of different metal and have different thicknesses.
U.S. Pat. No. 3,534,827 discloses a loudspeaker casing comprising an inner and an outer chamber as well as a duct communicating with the chambers.
Japanese patent publication 3 220 897 (Patent Abstracts of Japan, vol. 15, no. 506, E-1148) discloses a ventilation arrangement for allowing air flow in and out of the voice coil.
SUMMARY OF THE INVENTION
The aim of the present innovation is to produce a loudspeaker with a satisfactory frequency response over the whole voice frequency range of 16 Hz-22,000 Hz, with a considerably higher power transfer ratio than in known existing speakers and with minimal distortion components in the sound produced.
The loudspeaker according to the invention is such that the planar structure of the front surface of the diaphragm generates such a vibrating diaphragm wherein the diaphragm forms essentially a spherical surface. The sound issuing from such a front surface is evenly distributed and free of the distortions referred to above. The loudspeaker has only one controller and no distribution filter is required.
According to one advantageous embodiment of the invention the loudspeaker casing is compartmentalized into a system of chambers that dampen the vibration of the diaphragm. This regulates air flows inside the casing and thereby affects the v
REFERENCES:
patent: 1815944 (1931-07-01), Gumaer
patent: 1863072 (1932-06-01), Smythe
patent: 3534827 (1970-10-01), Heidrich
patent: 3586121 (1971-06-01), Sotome
patent: 3708035 (1973-01-01), Sotome
Patent Abstracts of Japan, vol. 15, No. 506, E-1148, abstract of JP, A, 3-220897 (Matsushita Electric Ind Co Ltd), 30 Sep. 1991.
Dang Khanh
Transducer Valley Inc.
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