WAVEGUIDE ELECTROACOUSTICAL TRANSDUCING

• US 20090214066A1
• Filed: 02/21/2008
• Published: 08/27/2009
• Est. Priority Date: 02/21/2008
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Hoefler, Jeffrey J., Parker, Robert Preston, Freeman, Eric J.
• Granted Patent: US 8,351,629 B2
• Time in Patent Office: Days
• US Class Current: 381/339
• CPC Class Codes: H04R 1/2857 for loudspeaker transducers

Abstract

A loudspeaker assembly, including an acoustic waveguide; an acoustic driver mounted in the waveguide so that a first surface radiates sound waves into the waveguide so that the sound waves are radiated from the waveguide; and an acoustic volume acoustically coupled to the acoustic waveguide for increasing the amplitude of the sound waves radiated from the acoustic waveguide.

Claims

1. A loudspeaker assembly, comprising:

an acoustic waveguide;

an acoustic driver mounted in the waveguide so that a first surface radiates sound waves into the waveguide so that the sound waves are radiated from the waveguide; and

an acoustic volume having dimensions acoustically coupled to the acoustic waveguide at a position along the waveguide, wherein the position and the dimensions cause an increase in the amplitude of the sound waves radiated from the acoustic waveguide.

2. A loudspeaker assembly according to claim 1, wherein the acoustic waveguide is substantially lossless.

3. A loudspeaker assembly according to claim 1, wherein the acoustic volume increases the amplitude of sound waves of a wavelength equal to the effective acoustic length of the waveguide.

4. A loudspeaker assembly according to claim 1, the acoustic waveguide having curved walls forming walls of an acoustic volume acoustically coupled to the acoustic waveguide to increase the acoustic radiation from the waveguide.

5. A loudspeaker assembly according to claim 4, wherein the acoustic volume is tear drop shaped.

6. A loudspeaker assembly according to claim 4, the waveguide walls forming walls of another acoustic volume coupled to the acoustic waveguide.

7. A loudspeaker assembly according to claim 4, further comprising electronic components positioned in the acoustic volume.

8. A loudspeaker assembly in accordance with claim 4, further comprising a coupling volume for acoustically coupling the acoustic waveguide to the acoustic volume, the combination of the coupling volume and the acoustic volume forming a Helmholtz resonator having a Helmholtz resonance frequency that is outside the operating range of the loudspeaker assembly.

9. A loudspeaker assembly according to claim 1, wherein the acoustic driver is mounted so that a second surface of the acoustic driver radiates directly to the environment.

10. A loudspeaker assembly according to claim 1, the waveguide comprising multiple curved sections substantially defining the acoustic volume.

11. A loudspeaker assembly according to claim 10, the acoustic waveguide substantially defining another acoustic volume.

12. A loudspeaker assembly according to claim 10, wherein the acoustic volume is teardrop shaped.

13. A loudspeaker assembly according to claim 1, the waveguide having an effective acoustic length, the acoustic volume having acoustic paths each having

a length that is less than 10% of the effective acoustic length of the loudspeaker assembly, or

a length that is greater than 10% of the effective acoustic length of the loudspeaker assembly and that is within a range of lengths that does not result in a dip in a frequency response.

14. A loudspeaker assembly according to claim 13, the acoustic volume comprising a baffle structure causing the length of an acoustic path to be within the range of lengths.

15. A loudspeaker assembly according to claim 1, the waveguide having a substantially constant cross-sectional area.

16. A loudspeaker assembly according to claim 1, wherein a closed end of the waveguide adjacent the acoustic driver has a larger cross-sectional area than an open end of the waveguide.

17. A loudspeaker assembly, comprising:

an acoustic driver;

an acoustic waveguide with substantially continuous walls acoustically coupled to the acoustic driver so that a first surface of the acoustic driver radiates into the acoustic waveguide and so that the waveguide radiates acoustic energy from an open end of the waveguide, the waveguide comprising structure that increases the amplitude of the acoustic radiation that is radiated from the open end of the waveguide.

18. A loudspeaker assembly according to claim 17, wherein the structure for increasing the amplitude comprises an acoustic volume, acoustically coupled to the acoustic waveguide.

19. A loudspeaker assembly according to claim 17, wherein the acoustic waveguide is substantially lossless.

20. A loudspeaker assembly according to claim 17, the acoustic waveguide having curved walls forming walls of an acoustic volume acoustically coupled to the acoustic waveguide to increase the acoustic radiation from the waveguide.

21. A loudspeaker assembly according to claim 20, wherein the acoustic waveguide walls form walls of a teardrop shaped acoustic volume.

22. A loudspeaker assembly according to claim 20, the waveguide walls forming walls of another acoustic volume coupled to the acoustic waveguide.

23. A loudspeaker assembly according to claim 20, further comprising electronic components positioned in the acoustic volume.

24. A loudspeaker assembly in accordance with claim 17, further comprising a coupling volume for acoustically coupling the acoustic waveguide to the acoustic volume, the combination of the coupling volume and the acoustic volume forming a Helmholtz resonator having a Helmholtz resonance frequency that is outside the operating range of the loudspeaker assembly.

25. A loudspeaker assembly according to claim 17, wherein the acoustic driver is mounted so that a second surface of the acoustic driver radiates into the environment.

26. A loudspeaker assembly according to claim 17, the waveguide comprising multiple curved sections substantially defining at least one acoustic volume, coupled to the acoustic waveguide.

27. A loudspeaker assembly according to claim 26, the acoustic waveguide substantially defining another acoustic volume, coupled to the acoustic waveguide.

28. A loudspeaker assembly according to claim 26, wherein the acoustic volume is teardrop shaped.

29. A loudspeaker assembly according to claim 17, the waveguide having an effective acoustic length, the acoustic volume having acoustic paths each having

a length that is less than 10% of the effective acoustic length of the loudspeaker assembly, or

a length that is greater than 10% of the effective acoustic length of the loudspeaker assembly and that is within a range of lengths that does not result in a dip in a frequency response.

30. A loudspeaker assembly according to claim 29, the acoustic volume comprising a baffle structure causing the length of an acoustic path to be within the range of lengths.

31. A loudspeaker assembly according to claim 17, wherein the waveguide has a substantially constant cross-sectional area.

32. A loudspeaker assembly according to claim 17, wherein the waveguide has a cross sectional area at a closed end adjacent the acoustic driver than at an open end.

33. A loudspeaker apparatus comprising:

an acoustic waveguide;

an acoustic driver having a first radiating surface and a second radiating surface, the acoustic driver mounted to the waveguide so that the first surface radiates acoustic energy into the acoustic waveguide so that the acoustic energy is radiated from the waveguide;

the loudspeaker apparatus characterized by a cancellation frequency at which radiation from the second surface is out of phase with the radiation from the waveguide, resulting in destructive interference between the radiation from the waveguide and the radiation from the second surface, resulting in a reduction in acoustic output from the loudspeaker apparatus at the cancellation frequency; and

an acoustic volume, acoustically coupled to the waveguide to increase the amplitude of the radiation from the waveguide resulting in less reduction in acoustic output from the loudspeaker apparatus at the cancellation frequency.