Acoustic device having an electro-acoustic transducer mounted to a passive radiator diaphragm

1. An acoustic device, comprising:

a first acoustic cavity that is substantially air tight;

a second acoustic cavity that is substantially air tight;

an enclosure that defines the first and second acoustic cavities;

a first passive radiator comprising a first passive radiator diaphragm having a rear surface which is exposed to the first acoustic cavity;

a second passive radiator comprising a second passive radiator diaphragm having a front surface which is exposed to the first acoustic cavity, and a rear surface which is exposed to the second acoustic cavity;

a third passive radiator comprising a third passive radiator diaphragm having a rear surface which is exposed to the second acoustic cavity; and

a first electro-acoustic transducer supported on the second passive radiator diaphragm,

wherein the first electro-acoustic transducer is arranged such that a first radiating surface of the first electro-acoustic transducer radiates acoustic energy into the first acoustic chamber and a second radiating surface of the first electro-acoustic transducer radiates acoustic energy into the second acoustic chamber,

wherein the first passive radiator has a first effective radiating area; the second passive radiator has a second effective radiating area, inclusive of an effective radiating area of the electro-acoustic transducer; and the third passive radiator has a third effective radiating area,

wherein the first, second, and third effective radiating areas are substantially the same,

wherein the first passive radiator diaphragm is coupled to the enclosure by a first suspension element, the second passive radiator diaphragm is coupled to the enclosure by a second suspension element, and the third passive radiator diaphragm is coupled to the enclosure by a third suspension element,

wherein the first passive radiator has a first effective mass and the first suspension element has a first effective stiffness,

wherein the second passive radiator has a second effective mass, inclusive of the mass of the electro-acoustic transducer, and the second suspension element has a second effective stiffness,

wherein the third passive radiator has a third effective mass and the third suspension element has a third effective stiffness, and

wherein the ratio of the first effective stiffness to the first effective mass is substantially equal to the ratio of the second effective stiffness to the second effective mass, which is substantially equal to the ratio of the third effective stiffness to the third effective mass.

2. The acoustic device of claim 1 , wherein the first effective mass is substantially less than the second effective mass.

3. The acoustic device of claim 2 , wherein the third effective mass is substantially less than the second effective mass.

4. The acoustic device of claim 1 wherein the first passive radiator diaphragm, the second passive radiator diaphragm, and the third passive radiator diaphragm are each configured to vibrate, relative to the enclosure, along a common vibration axis.

5. The acoustic device of claim 4 , wherein the first electro-acoustic transducer includes a transducer diaphragm, a motor, and a surround that couples the transducer diaphragm to the second passive radiator diaphragm, and wherein the motor drives motion of the transducer diaphragm, relative to the second passive radiator diaphragm, along the common vibration axis.

6. The acoustic device of claim 1 , wherein the first passive radiator diaphragm and the second passive radiator diaphragm are each configured to vibrate, relative to the enclosure, along a common vibration axis.

7. The acoustic device of claim 6 , wherein the first electro-acoustic transducer includes a transducer diaphragm, a motor, and a surround that couples the transducer diaphragm to the second passive radiator diaphragm, and wherein the motor drives motion of the transducer diaphragm, relative to the second passive radiator diaphragm, along the common vibration axis.

8. The acoustic device of claim 1 , further comprising a first enclosure which defines the first acoustic cavity, and a second enclosure that defines the second acoustic cavity, wherein the first enclosure is mounted to the second passive radiator such that the first enclosure moves when the second passive radiator diaphragm vibrates.

9. The acoustic device of claim 8 , wherein the first passive radiator diaphragm is coupled to the first enclosure by a first suspension element such that the second passive radiator diaphragm can vibrate relative to the first enclosure, and the second passive radiator diaphragm is coupled to the second enclosure by a second suspension element such that the second passive radiator diaphragm can vibrate relative to the second enclosure.

10. The acoustic device of claim 9 , wherein the first passive radiator diaphragm, and the second passive radiator diaphragm both vibrate along a common vibration axis.

11. The acoustic device of claim 10 , wherein the first electro-acoustic transducer includes a transducer diaphragm, a motor, and a surround that couples the transducer diaphragm to the second passive radiator diaphragm, and wherein the motor drives motion of the transducer diaphragm, relative to the second passive radiator diaphragm, along the common vibration axis.

12. An acoustic device, comprising:

a first acoustic cavity that is substantially air tight;

a second acoustic cavity that is substantially air tight;

a first passive radiator comprising a first passive radiator diaphragm having a rear surface which is exposed to the first acoustic cavity;

a second passive radiator comprising a second passive radiator diaphragm having a front surface which is exposed to the first acoustic cavity, and a rear surface which is exposed to the second acoustic cavity;

a first electro-acoustic transducer supported on the second passive radiator diaphragm;

a third acoustic cavity that is substantially air tight;

a third passive radiator comprising a third passive radiator diaphragm having a rear surface which is exposed to the third acoustic cavity;

a fourth passive radiator comprising a fourth passive radiator diaphragm having a front surface which is exposed to the third acoustic cavity, and a rear surface which is exposed to the second acoustic cavity;

a second electro-acoustic transducer supported on the fourth passive radiator diaphragm,

a first enclosure which defines the first acoustic cavity; and

a second enclosure that defines the second acoustic cavity,

wherein the first enclosure is mounted to the second passive radiator such that the first enclosure moves when the second passive radiator diaphragm vibrates,

wherein the first electro-acoustic transducer is arranged such that a first radiating surface of the first electro-acoustic transducer radiates acoustic energy into the first acoustic chamber and a second radiating surface of the first electro-acoustic transducer radiates acoustic energy into the second acoustic chamber,

wherein the second electro-acoustic transducer is arranged such that a first radiating surface of the second electro-acoustic transducer radiates acoustic energy into the third acoustic chamber and a second radiating surface of the second electro-acoustic transducer radiates acoustic energy into the second acoustic chamber,

wherein the first passive radiator diaphragm is coupled to the first enclosure by a first suspension element such that the second passive radiator diaphragm can vibrate relative to the first enclosure, and the second passive radiator diaphragm is coupled to the second enclosure by a second suspension element such that the second passive radiator diaphragm can vibrate relative to the second enclosure, and

wherein the first passive radiator diaphragm, and the second passive radiator diaphragm both vibrate along a common vibration axis.

13. The acoustic device of claim 12 , further comprising a third enclosure that defines the third acoustic cavity, wherein the third enclosure is mounted to the fourth passive radiator such that the third enclosure moves when the fourth passive radiator diaphragm vibrates.

14. The acoustic device of claim 13 , wherein the third passive radiator diaphragm is coupled to the third enclosure by a third suspension element such that the third passive radiator diaphragm can vibrate relative to the third enclosure, and the fourth passive radiator diaphragm is coupled to the second enclosure by a fourth suspension element such that the fourth passive radiator diaphragm can vibrate relative to the second enclosure.

15. The acoustic device of claim 14 , wherein the first, second, third, and fourth passive radiator diaphragms all vibrate along a common vibration axis.

16. The acoustic device of claim 15 , wherein each of the first and second electro-acoustic transducers includes a transducer diaphragm, a motor, and a surround that couples the transducer diaphragm to the second passive radiator diaphragm, and wherein the motors drive motion of the transducer diaphragms along the common vibration axis.

17. The acoustic device of claim 13 , wherein the movements of the third passive radiator diaphragm, the third enclosure, the fourth passive radiator diaphragm, and the second electro-acoustic transducer balance forces applied to the second enclosure due to movements of the first passive radiator diaphragm, the first enclosure, the second passive radiator diaphragm, and the first electro-acoustic transducer.