Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having acoustic wave modifying structure
Patent
1992-10-02
1994-12-13
Kuntz, Curtis
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Having acoustic wave modifying structure
381153, 381159, 181156, 181199, H04R 2500, H05K 500, A47B 8106
Patent
active
053735641
ABSTRACT:
A high fidelity loudspeaker having a driver, e.g., a woofer in a housing, is rear-loaded by a folded passage, i.e., a transmission line, closed at one end by a loudspeaker and open to the environment at the other end. The line has a length equal to the quarter-wave length of the lowest desired frequency. Angled 45.degree. reflectors are used in the transmission line whereby an advancing planar wave from the rear of the speaker is produced from the rear hemispherical wave. The transmission line is conventionally stuffed with fibrous material, such as long fiber wool, which attenuates resonances, absorbs high frequencies and acts as a low pass filter. The acoustic output at the open end of the transmission line has high frequencies filtered out and a low frequency planar wave at maximum possible amplitude emitted in close phase with the front wave of the loudspeaker. This is accomplished by continuous reversal by flat reflectors in a contiguous array, with no discontinuity of reflection, utilizing reflection reversing surfaces. Thereby, a planar wave can be obtained in a predetermined length of passage. The rear planar wave emerges from the housing in substantially additive phase with the driver front wave.
REFERENCES:
patent: 4173266 (1979-11-01), Pizer et al.
patent: 4790408 (1988-12-01), Adair
patent: 4942939 (1990-07-01), Harrison
patent: 4969196 (1990-11-01), Nakamura
Howard M. Tremaine, "Audio Cyclopedia", 1959, p. 1107.
New York Audio Labs, "Time Aligned and Diffraction", vol. 2, No. 3 8/1981.
Spear Robert J.
Thornhill Alexander F.
Kuntz Curtis
Tran Sinh
Zalkind Albert M.
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