Abstract: An acoustic transducer for providing large displacements particularly at low acoustic frequencies is formed from a minimum of three curved shells which are attached to each other at their ends. The shells are driven by a ring or corresponding number of attached piezoelectric or magnetostrictive type rod or bar drivers. The curved shells are attached to the ends of the driver and vibrate with a magnified motion as the rods execute extensional motion. As the polygon expands the curved shells deform and produce additional motion in the same radial direction resulting in a large total displacement and corresponding large acoustic output.

Abstract: An electro-mechanical spring which provides amplified motion as well as a compliant structure for attachment, at the locations of maximum motion, to other mechanical or acoustical loads or elements. The spring produces motion in a directional orthogonal to the direction of a piezoelectric or magnetostrictive drive member connected along the major axis of a complete shell. The electro-mechanical spring provides a means for obtaining a low frequency large displacement piston type transducer.

Abstract: A directional flextensional transducer including a transducer shell capable of operation in odd and even drive modes and a transduction drive bar or the like. The transduction drive bar is excited in an even mode to impart extensional motion thereto and is simultaneously excited in an odd mode to impart inextensional motion thereto. The combined excitation causes the flextensional transducer shell to move unidirectionally.

Abstract: An acoustic transducer for providing large displacements particularly at low acoustic frequencies is formed from a minimum of three curved shells which are attached to each other at their ends. The shells are driven by a ring or corresponding number of attached piezoelectric or magnetostrictive type rod or bar drivers which take the form of a regular polygon. The curved shells are attached to the ends of the driver and vibrate with magnified motion as the rods execute extensional motion. As the polygon expands the curved shells deform and produce additional motional in the same radial direction resulting in a large total displacement and corresponding large acoustic output.

Abstract: A passive radiator, which may be a cone-type radiator is employed in a speaker system enclosure facing downwardly in the direction of the floor upon which the enclosure rests. The bottom wall supporting the passive radiator is preferably spaced a relatively short height above the floor by means of a plurality of legs such as four legs defining four output ports through which sound passes below the basic enclosure. The low frequency sound communicated through the four ports may be used to tune the resonator of the speaker system. With the use of the passive radiator maximum loading is obtained and interference effects are minimized. Also, upper base and mid-range internal reflections are prevented from being re-radiated. Because of the maximizing of loading a smaller passive radiator may be employed. Moreover, the concept of the passive radiator of this invention may be employed both in a single channel speaker system and a dual channel speaker system.