Abstract: An acoustic device with an open audio device structure that is configured to be carried on the head or upper torso of a user, a housing carried by the open audio device structure, the housing having opposed first and second ends, a flat diaphragm in the housing and comprising a front face and a rear face, the diaphragm configured to radiate front acoustic radiation from its front face and rear acoustic radiation from its rear face, wherein the front and rear acoustic radiations are out of phase, structure that supports the diaphragm such that the diaphragm can move relative to the housing, a primary magnet adjacent to the rear face of the diaphragm, a magnetic circuit that defines a path for magnetic flux of the primary magnet, a voice coil that is exposed to the magnetic flux and is configured to move the diaphragm up and down along a radiation axis that is normal to the front face of the diaphragm, and first and second sound-emitting outlets in the housing, wherein the first sound-emitting outlet is in or p

Abstract: An acoustic device with an open audio device structure that is configured to be carried on the head or upper torso of a user, a housing carried by the open audio device structure, the housing having opposed first and second ends, a flat diaphragm in the housing and comprising a front face and a rear face, the diaphragm configured to radiate front acoustic radiation from its front face and rear acoustic radiation from its rear face, wherein the front and rear acoustic radiations are out of phase, structure that supports the diaphragm such that the diaphragm can move relative to the housing, a primary magnet adjacent to the rear face of the diaphragm, a magnetic circuit that defines a path for magnetic flux of the primary magnet, a voice coil that is exposed to the magnetic flux and is configured to move the diaphragm up and down along a radiation axis that is normal to the front face of the diaphragm, and first and second sound- emitting outlets in the housing, wherein the first sound-emitting outlet is in or

Abstract: An acoustic device with an open audio device structure that is configured to be carried on the head or upper torso of a user, a housing carried by the open audio device structure, the housing having opposed first and second ends, a flat diaphragm in the housing and comprising a front face and a rear face, the diaphragm configured to radiate front acoustic radiation from its front face and rear acoustic radiation from its rear face, wherein the front and rear acoustic radiations are out of phase, structure that supports the diaphragm such that the diaphragm can move relative to the housing, a primary magnet adjacent to the rear face of the diaphragm, a magnetic circuit that defines a path for magnetic flux of the primary magnet, a voice coil that is exposed to the magnetic flux and is configured to move the diaphragm up and down along a radiation axis that is normal to the front face of the diaphragm, and first and second sound-emitting outlets in the housing, wherein the first sound-emitting outlet is in or p

Abstract: An acoustic device with an open audio device structure that is configured to be carried on the head or upper torso of a user, a housing carried by the open audio device structure, the housing having opposed first and second ends, a flat diaphragm in the housing and comprising a front face and a rear face, the diaphragm configured to radiate front acoustic radiation from its front face and rear acoustic radiation from its rear face, wherein the front and rear acoustic radiations are out of phase, structure that supports the diaphragm such that the diaphragm can move relative to the housing, a primary magnet adjacent to the rear face of the diaphragm, a magnetic circuit that defines a path for magnetic flux of the primary magnet, a voice coil that is exposed to the magnetic flux and is configured to move the diaphragm up and down along a radiation axis that is normal to the front face of the diaphragm, and first and second sound-emitting outlets in the housing, wherein the first sound-emitting outlet is in or p

Abstract: An acoustic device with an open audio device structure that is configured to be carried on the head or upper torso of a user, a housing carried by the open audio device structure, the housing having opposed first and second ends, a flat diaphragm in the housing and comprising a front face and a rear face, the diaphragm configured to radiate front acoustic radiation from its front face and rear acoustic radiation from its rear face, wherein the front and rear acoustic radiations are out of phase, structure that supports the diaphragm such that the diaphragm can move relative to the housing, a primary magnet adjacent to the rear face of the diaphragm, a magnetic circuit that defines a path for magnetic flux of the primary magnet, a voice coil that is exposed to the magnetic flux and is configured to move the diaphragm up and down along a radiation axis that is normal to the front face of the diaphragm, and first and second sound-emitting outlets in the housing, wherein the first sound-emitting outlet is in or p

Abstract: An acoustic device with an open audio device structure that is configured to be carried on the head or upper torso of a user, a housing carried by the open audio device structure, the housing having opposed first and second ends, a flat diaphragm in the housing and comprising a front face and a rear face, the diaphragm configured to radiate front acoustic radiation from its front face and rear acoustic radiation from its rear face, wherein the front and rear acoustic radiations are out of phase, structure that supports the diaphragm such that the diaphragm can move relative to the housing, a primary magnet adjacent to the rear face of the diaphragm, a magnetic circuit that defines a path for magnetic flux of the primary magnet, a voice coil that is exposed to the magnetic flux and is configured to move the diaphragm up and down along a radiation axis that is normal to the front face of the diaphragm, and first and second sound-emitting outlets in the housing, wherein the first sound-emitting outlet is in or p

Abstract: A loudspeaker includes an acoustic diaphragm, an oscillatory force source, a lever coupling the oscillatory force source to the acoustic diaphragm, and a pivot coupled to the lever such that the lever moves in an arcuate path about the pivot when the oscillatory force source applies a force to the lever. The pivot includes at least one torsion bushing. The at least one torsion bushing includes a first member, a second member coupled to the lever and movable relative to the first member, and an elastomeric member coupling the first member to the second member. Either the first member or the second member is coupled to and moves with the lever. An outer surface of the elastomeric member is coupled to the second member via mechanical compression.

Abstract: An induction cooking utensil is constructed such that it cooks food within its chamber while maintaining a relatively cool outer surface (e.g., preferably an outer surface that is cool enough to pick up with one's bare hands). The cooking utensil includes an inner wall that is made at least in part of an electrically conductive material and an outer wall that is made at least in part of the electrically non-conductive material. A reflective layer, a vacuum-sealed thermal insulator and/or a gas more resistant to conducting heat than air is disposed between the inner and outer walls to resist the transfer of heat from the inner wall to the outer wall.

Abstract: A loudspeaker includes an acoustic diaphragm, an oscillatory force source, a lever coupling the oscillatory force source to the acoustic diaphragm, and a pivot coupled to the lever such that the lever moves in an arcuate path about the pivot when the oscillatory force source applies a force to the lever. The pivot includes at least one torsion bushing. The at least one torsion bushing includes a first member, a second member coupled to the lever and movable relative to the first member, and an elastomeric member coupling the first member to the second member. Either the first member or the second member is coupled to and moves with the lever. An outer surface of the elastomeric member is coupled to the second member via mechanical compression.

Abstract: An electrical apparatus to sense current through a load includes a first input terminal having a first input voltage relative to a reference, a second input terminal having a second input voltage relative to the reference, a first load terminal of the load having a first load voltage relative to the reference, a second load terminal of the load having a second load voltage relative to the reference, a first current sensing element connected between the first input terminal and the first load terminal and a second current sensing element connected between the second input terminal and the second load terminal. A first sense voltage is determined by a relationship between the first input voltage and the second load voltage and a second sense voltage is determined by a relationship between the second input voltage and the first load voltage.

Abstract: An induction cooking utensil is constructed such that it cooks food within its chamber while maintaining a relatively cool outer surface (e.g., preferably an outer surface that is cool enough to pick up with one's bare hands). The cooking utensil includes an inner wall that is made at least in part of an electrically conductive material and an outer wall that is made at least in part of the electrically non-conductive material. A reflective layer, a vacuum-sealed thermal insulator and/or a gas more resistant to conducting heat than air is disposed between the inner and outer walls to resist the transfer of heat from the inner wall to the outer wall.

Abstract: An induction cooking utensil is constructed such that it cooks food within its chamber while maintaining a relatively cool outer surface (e.g., preferably an outer surface that is cool enough to pick up with one's bare hands). The cooking utensil includes an inner wall that is made at least in part of an electrically conductive material and an outer wall that is made at least in part of the electrically non-conductive material. A reflective layer, a vacuum-sealed thermal insulator and/or a gas more resistant to conducting heat than air is disposed between the inner and outer walls to resist the transfer of heat from the inner wall to the outer wall.

Abstract: An electrical apparatus to sense current through a load includes a first input terminal having a first input voltage relative to a reference, a second input terminal having a second input voltage relative to the reference, a first load terminal of the load having a first load voltage relative to the reference, a second load terminal of the load having a second load voltage relative to the reference, a first current sensing element connected between the first input terminal and the first load terminal and a second current sensing element connected between the second input terminal and the second load terminal. A first sense voltage is determined by a relationship between the first input voltage and the second load voltage and a second sense voltage is determined by a relationship between the second input voltage and the first load voltage.

Abstract: An audio system including an audio power amplifier, a transducer electrically connected to the audio power amplifier, an enclosure coupled to the transducer, and a secondary resonant element coupled to the enclosure. An electrical feedback signal representative of the transducer current is negatively fed back to the audio power amplifier to synthesize a positive output impedance.

Abstract: An electro-acoustic transducer has an electro-magnetically driven moving dome and a phase plug having a body and a dome-interface surface, with a compression cavity formed between the dome and the dome-interface surface. The phase plug includes at least first and second annular slots beginning at the dome-interface surface and extending a first depth into the body of the phase plug. The first and second slots are separated by a bridge element at the dome-interface surface and joined by a first bridge passage at the first depth beneath the dome-interface surface. The phase plug also includes an exit slot coupling the bridge passage to a throat at a second depth in the body of the phase plug.

Abstract: An armature for a linear motor is described. The armature includes a first of a pair of magnetic structures comprising a first plurality of maglettes each having a magnetic polarity vector; an angle between two adjacent magnetic polarity vectors in the first plurality of maglettes having a first magnitude; and a second of the pair of magnetic structures comprising a second plurality of maglettes each having a magnetic polarity vector; an angle between two adjacent magnetic polarity vectors in the second plurality of maglettes having a second magnitude, the first plurality of maglettes including a first outer maglette that is adjacent to a second outer maglette of the second plurality of maglettes, an angle between the magnetic polarity vectors of the first and second outer maglettes having a third magnitude that is different than at least one of the first and the second magnitudes.

Abstract: An electro-acoustic transducer has an electro-magnetically driven moving dome and a phase plug having a body and a dome-interface surface, with a compression cavity formed between the dome and the dome-interface surface. The phase plug includes at least first and second annular slots beginning at the dome-interface surface and extending a first depth into the body of the phase plug. The first and second slots are separated by a bridge element at the dome-interface surface and joined by a first bridge passage at the first depth beneath the dome-interface surface. The phase plug also includes an exit slot coupling the bridge passage to a throat at a second depth in the body of the phase plug.

Abstract: An induction cooking system including one or more methods or apparatus for identifying items of cookware. The identifying may include identifying whether in use, the temperature of the outside surface of the element of cookware is significantly lower than the temperature of the inside surface. The methods may include one or more of measuring impedance, communicating information by RF radiation, or measuring reactance.

Abstract: A waveguide system for radiating sound waves. The system includes a low loss waveguide for transmitting sound waves, having walls are tapered so that said cross-sectional area of the exit end is less than the cross-sectional area of the inlet end. In a second aspect of the invention, a waveguide for radiating sound waves, has segments of length approximately equal to A ? ( y ) = A inlet ? [ 1 - 2 ? Y B + ( y B ) 2 ] where l is the effective length of said waveguide and n is a positive integer. The product of a first set of alternating segments is greater than the product of a second set of alternating segments, in one embodiment, by a factor of three. In a third aspect of the invention, the first two aspects are combined.

Abstract: An armature for a linear motor is described. The armature includes a first of a pair of magnetic structures comprising a first plurality of maglettes each having a magnetic polarity vector; an angle between two adjacent magnetic polarity vectors in the first plurality of maglettes having a first magnitude; and a second of the pair of magnetic structures comprising a second plurality of maglettes each having a magnetic polarity vector; an angle between two adjacent magnetic polarity vectors in the second plurality of maglettes having a second magnitude, the first plurality of maglettes including a first outer maglette that is adjacent to a second outer maglette of the second plurality of maglettes, an angle between the magnetic polarity vectors of the first and second outer maglettes having a third magnitude that is different than at least one of the first and the second magnitudes.