Push-pull electromagnetic transducer with increased Xmax

An electromagnetic transducer comprising:

• (a) a push-pull magnetic circuit including,
• a top plate defining an upper magnetic air gap,
• a bottom plate defining a lower magnetic air gap,
• a total available magnetic air gap height comprising the upper and lower magnetic air gaps, and
• a magnet providing magnetic flux over the upper magnetic air gap in a first direction and magnetic flux over the lower magnetic air gap in a second direction opposite the first direction;
• and
• (b) a voice coil assembly including,
• a bobbin,
• an upper voice coil having windings coupled to the bobbin,
• a lower voice coil having windings coupled to the bobbin, and
• a total available voice coil height comprising the upper and lower voice coils:
• (c) wherein the upper and lower voice coils are coupled to the bobbin at respective positions such that BOTH,
• less than 100% of the total available magnetic air gap height contains voice coil windings, AND
• less than 100% of the total available voice coil height is within the magnetic air gaps;
• a second such push-pull magnetic circuit;
• and
• two additional voice coils arranged in the second magnetic circuit as the first and second voice coils are arranged in their magnetic circuit.

An electromagnetic transducer comprising:

• (a) a push-pull magnetic circuit including,
• a top plate defining an upper magnetic air gap,
• a bottom plate defining a lower magnetic air gap,
• a total available magnetic air gap height comprising the upper and lower magnetic air gaps, and
• a magnet providing magnetic flux over the upper magnetic air gap in a first direction and magnetic flux over the lower magnetic air gap in a second direction opposite the first direction;
• and
• (b) a voice coil assembly including,
• a bobbin,
• an upper voice coil having windings coupled to the bobbin,
• a lower voice coil having windings coupled to the bobbin, and
• a total available voice coil height comprising the upper and lower voice coils;
• (c) wherein the upper and lower voice coils are coupled to the bobbin at respective positions such that BOTH,
• less than 100% of the total available magnetic air gap height contains voice coil windings, AND
• less than 100% of the total available voice coil height is within the magnetic air gaps;
• a second top plate defining a second upper magnetic air gap above the upper magnetic air gap;
• a second bottom plate defining a second lower magnetic air gap below the lower magnetic air gap;
• the at least one magnet further providing magnetic flux over the second upper magnetic air gap in the first direction and magnetic flux over the second lower air gap in the second direction.

An audio speaker comprising:

• (a) a basket;
• (b) a motor structure coupled to the basket and including,
• at least one push-pull magnetic circuit each including,
• a top plate defining an upper magnetic air gap, and
• a bottom plate defining a lower magnetic air gap;
• and
• (c) a diaphragm assembly coupled to the basket and including,
• a diaphragm,
• a bobbin coupled to the diaphragm, and
• a pair of voice coils coupled to the bobbin for each of the push-pull magnetic circuits, wherein the voice coils are coupled to the bobbin at positions such that the voice coils extend axially inward from their corresponding plates;
• (d) wherein, within a linear travel region of the audio speaker, in each of the push-pull magnetic circuits,
• in a push side, only a portion of one of its magnetic air gap and its voice coil is actively engaged with the other first one having a height that is shorter than or equal to a height of the second one,
• in a pull side, only a portion of one of its magnetic air gap and its voice coil is actively engaged with the other one having a height that is shorter than or equal to a height of the other, and
• a cumulative height of the portions is substantially equal to 50% of a cumulative total height of the ones that are actively engaged with the others.

An apparatus comprising:

• a moving magnet motor structure including,
• a yoke,
• a push-pull magnetic circuit having an upper plate and a lower plate magnetically coupled to opposite sides of a magnet, the upper plate and the lower plate defining an upper magnetic air gap and a lower magnetic air gap, respectively, between themselves and the yoke, and
• an upper voice coil and a lower voice coil coupled to the yoke,
• wherein, at a resting postion the upper voice coil and the upper magnetic air gap are partially engaged such that only part of each is engaged with the other, and the lower voice coil and the lower magnetic air gap are partially engaged such that only part of each is engaged with the other;
• and
• a bobbin coupled to,
• the upper plate,
• the magnet, and
• the lower plate.

A method of operating an electromagnetic transducer, the method comprising:

• conducting magnetic flux over an upper magnetic air gap in a first direction and over a lower magnetic air gap in second direction opposite the first direction, in a push-pull magnetic circuit;
• conducting at least one alternating current electrical voice signal through a pair of voice coils disposed within the magnetic circuit and including an upper voice coil having windings disposed in the upper magnetic air gap and a lower voice coil having windings disposed in the lower magnetic air gap;
• continuing to move the voice coils until at least one of them enters one of,
• (a) a braking magnetic air gap which is not in the push-pull magnetic circuit, and
• (b) the magnetic air gap in which the other of the voice coils resides during linear travel of the electromagnetic transducer;
• wherein, at a centered position of the voice coils with respect to the push-pull magnetic circuit, BOTH
• (1) less than 100% of each magnetic air gap contains voice coil windings, AND
• (2) less than 100% of each voice coil's windings are in its respective magnetic air gap;
• and
• in response to the alternating current electrical voice signal, moving the voice coils until exactly one voice coil and its magnetic air gap are inactive.