The coaxial flat-plane speaker is a new and unique approach to direct radiator plane diaphragm loudspeakers, and provides improved performance unobtainable from conventional designs. 1) Enhancement of sound imaging by keeping the broadening of the sound source to a minimum. This major feature was realized by coaxially mounting four flat-plane diaphragm speakers, each handling a portion of the total sound spectrum from near sub-sonic frequencies up to super-sonic frequencies so that the acoustic centers of all four radiators are perfectly aligned in one plane. This causes the arrival times and sources of sounds from all diaphragms to be equal. The time delays between all frequencies can therefore be held to a minimum. 2) A flat and smooth frequency response has been obtained by eliminating the conventional cone diaphragm's cavity with its inherent resonances and break-up frequency characteristics. 3) Piston motion over a comparatively wide range of frequencies has been realized by adopting a sandwich type construction consisting of two polymer-composite sheets with an aluminum foil honeycomb core bonded in between. The polymer-graphite skin material is designed to have a high internal loss factor while the core material ensures high flexural rigidity. This unique construction yields a plane diaphragm which maintains piston motion over a wide range of frequencies with flat frequency characteristics and excellent transient response.
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