| 摘要 |
PROBLEM TO BE SOLVED: To provide a flat speaker that applies string vibration to a square vibration membrane applied with tensile tension uniaxially so as to enhance the low frequency reproduction capability and the sound pressure and to attain constant stable reproduction. SOLUTION: While a short side and its vicinity of a rectangular vibration membrane 12 are welded or bonded to a support frame 13 to apply tensile tension to the membrane 12 in the longitudinal direction, an exciter 15 pressed into contact with a rear face of the membrane 12 via a coupler 14 applies string vibration to the membrane 12. The presence of many resonance frequencies being the features of the membrane 12 where tension from a loop of vibration to the circumferential edge changes depending on the azimuth produces a sufficient broad reproduced frequency band and the loop excited in the string vibration is vibrated in maximum amplitude, then the entire membrane 12 is largely driven in forward/backward directions to attain sufficient low frequency reproduction. The tensile tension given to the rectangular membrane 12 is simultaneously variably adjusted to realize a flat frequency characteristic extended widely over medium and high frequencies.
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