Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Mounting or support feature of housed loudspeaker
Reexamination Certificate
1997-04-15
2001-11-20
Mei, Xu (Department: 2644)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Mounting or support feature of housed loudspeaker
C381S348000, C381S352000, C381S353000, C181S151000, C181S155000, C181S198000
Reexamination Certificate
active
06320971
ABSTRACT:
TECHNICAL FIELD
This invention relates to a cabinet where little standing waves are generated, particularly to a speaker system comprising a cabinet suitable for reproducing high fidelity sounds, and a method for improving sound quality thereof.
BACKGROUND ART
Hitherto, a closed type cabinet, a bass-reflex type cabinet and a non-back baffle type cabinet have been known as a speaker cabinet. In the conventional cabinets, standing waves are generated by resonance of air inside the cabinet. The standing waves cause various problems as follows:
(1) The standing waves interrupt movement faithful to signals of a diaphragm of a speaker unit. As a result, an output sound frequency characteristic is disturbed and reproduced sound is distorted.
(2) A wall surface of the cabinet resonates with standing waves to produce sounds of the cabinet. A reproduced sound accompanied by the sounds of cabinet is different from an original sound. Also, the reproduced sound sounds as if it winds round the cabinet and has little expansion.
(3) A resonant sound of the standing waves leaks through the diaphragm of the speaker unit or a wall of the cabinet. Consequently, a specific sound of the reproduced sound has reverberation and is not clear. For solving these problems, various proposals have been made.
For example, in regard to the above problem (1), there have been proposed a method for filling up the cabinet with a sound absorbing material; a method for using a perforated sound absorbing board (Japanese U.M. Publication [JITSUKOSHO] No. 49-27241); a method for using a perforated sound absorbing board together with a sound absorbing material (Japanese U. M. Publication [JITSUKAISHO] No. 54-3930); a method for setting a sound reflecting board (Japanese U. M. Publication [JITSUKOSHO] No. 57-49492); a method for using a honeycomb core together with a sound absorbing material (Japanese Patent Publication [TOKUKOSHO] No. 58-45236); and a method for providing a sound absorbing cabinet inside the cabinet (Japanese Patent Publication [TOKUKOSHO] No. 61-61597. For the problem (2), it has been proposed that walls of a cabinet are thickened. For the problem (3), a method for covering an opening of a frame of a speaker unit with a sound absorbing material has been known.
However, these proposals have the following disadvantages.
(1) In case the cabinet is filled with the sound absorbing material, a lively, dynamic sound can not be reproduced. With the perforated board, only a special standing wave having a wave length corresponding to a size of the perforation can be absorbed to thereby have little absorbing effect. Thus, a plurality of standing waves is generated in the cabinet, which results in no practical use. In case the perforated board is used together with the sound absorbing material, various problems accompanied by mal-effects of the sound absorbing material arise. In case the sound reflecting board is used to scatter a sound, it is necessary to select a material, size, shape and setting direction of the sound reflecting board according to a direction and a wave length of the standing wave. Thus, it is difficult to cope with many standing waves. Further, in case an uneven diffusion reflecting structure comprising the sound reflecting board is formed on an inner surface of the cabinet, an effective volume of the cabinet decreases. The honeycomb type core has a large total opening area so that it has an effect only for a specific sound. When the honeycomb core is used together with a sound absorbing material, a reproduced sound is accompanied by a mal-effect of the sound absorbing material. It has been proposed that a sound absorbing cabinet is provided in the cabinet. However, the purpose is to raise a reproduced sound pressure level by resonating with a sound of specific frequency. The sound absorbing cabinet having small internal loss makes a reproduced sound an unnatural sound accompanied by a reverberation, in resonance with a sound having a specific frequency, if used in a wide range sound reproducing speaker system.
(2) In case the wall of the speaker cabinet is since the standing waves is not suppressed, the problem of the diaphragm of the speaker unit can not be solved.
(3) In case the opening of the frame of the speaker unit is covered with the sound absorbing material, a large quantity of the sound absorbing material causes a mal-effect to a tone quality. Also, it is difficult to eliminate mal-effects of the standing waves having frequencies less than 300 Hz with only the sound absorbing material.
Accordingly, the present invention is to provide a speaker system which can reproduce a clear bass sound and a stereophonic sound having an expanded sound field and a method for improving sound quality thereof.
DISCLOSURE OF THE INVENTION
An object of the present invention is accomplished by a speaker system wherein a cabinet has a space enclosed by partition walls therein, the partition walls are formed of a material having high internal loss and semi-transmission for a plurality of standing waves, a total capacity of the space is more than one tenth of a capacity of the cabinet, and a closed end of the space is positioned between one-half and four-fifths of a distance from a longitudinal end of the cabinet to the other. Also, a ratio of cross-sections of the space and the cabinet is preferably larger than one to five in the cross-section crossing the longitudinal direction of the cabinet. The space may be replaced by a plurality of spaces of different dimensions. Also, a total area of opening areas of the space surrounded by the partition walls is preferably less than one tenth of a total surface area of the partition walls. Further, the partition walls may have a density per area of more than 0.01 g/cm
2
to less than 1.0 g/cm
2
and have a density per volume of more than 0.1 g/cm
3
. The partition walls may be made of paper. The space may be enclosed by the partition walls and the acoustic isolation walls. The space also may be enclosed by the partition walls, the acoustic isolation walls and a reinforcing member for the acoustic isolation walls. The effect of the present invention is also fully exhibited by the speaker system having the space formed of a paper box.
REFERENCES:
patent: 1975201 (1934-10-01), Elworthy
patent: 3327808 (1967-06-01), Shaper
patent: 3684051 (1972-08-01), Hopkins
patent: 3978941 (1976-09-01), Siebert
patent: 4398619 (1983-08-01), Daniel
patent: 4750585 (1988-06-01), Collings
patent: A-3927178 (1991-02-01), None
patent: A-659818 (1951-10-01), None
patent: 0186191 (1985-09-01), None
The Radio Technology, article from the magazine for audiophile, Dec. 1, 1994.
Supplementary European Search Report in the European Patent Application No. 93900401.6 corresponding to the present application, including copies of the first pages of the references cited in the report.
Reference 1 Remarks about GA-A-659818.
Reference 2 (Referential material regarding technical matters such as “voice coil impedance”).
Official Communication dated Oct. 5, 1999 from the EPO.
Bracewell Sanders Peper Martin
Mei Xu
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