Ferrofluid Centered Voice Coil Speaker

Abstract

An audio speaker has a driver unit having a support frame with a central portion forming a magnetic structure defining an annular gap around a central magnetic post, a vibration system having a diaphragm and a voice coil, the voice coil is attached to one side of the diaphragm where the vibration system is fixed to the support frame and where the voice coil is movably mounted in the annular gap, and a magnetic fluid disposed in the annular gap only in a space between one side of the voice coil and a surface of the annular gap having a higher magnetic flux density.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified, cross-sectional view of one embodiment of the present invention showing an audio speaker with an annular magnet.

FIG. 2 is a simplified, cross-sectional view of another embodiment of the present invention showing an audio speaker with a magnet incorporated into the central post of the driver unit.

Claims

1. An audio speaker comprising: a driver unit having a support frame with a central portion forming a magnetic structure defining an annular gap around a central magnetic post;a vibration system having a diaphragm and a voice coil, said voice coil attached to one side of said diaphragm wherein said vibration system is fixed to said support frame and wherein said voice coil is movably mounted in said annular gap; anda magnetic fluid disposed in said annular gap only in a space between one side of said voice coil and a surface of said annular gap having a higher magnetic flux density.

2. The audio speaker of claim 1 wherein said magnetic fluid has a magnetization in the range of about 100 to about 600 Gauss.

3. The audio speaker of claim 2 wherein said magnetic fluid has a magnetization in the range of about 200 to about 500 Gauss.

4. The audio speaker of claim 3 wherein said magnetic fluid has a magnetization in the range of about 300 to about 400 Gauss.

5. The audio speaker of claim 1 wherein said magnetic fluid has a higher magnetization when said audio speaker has a voice coil with higher excursion and lower magnetic field.

6. The audio speaker of claim 1 wherein said magnetic fluid has a lower magnetization when said audio speaker has a voice coil with lower excursion and higher magnetic field.

7. The audio speaker of claim 1 wherein said voice coil has a tubular form of sufficient length to prevent the migration of said magnetic fluid at a distal end of said voice coil from said one side of said voice coil to a second side of said voice coil.

8. The audio speaker of claim 7 wherein said tubular form of said voice coil has a solid surface.

9. The audio speaker of claim 1 wherein said one side of said voice coil is between an outside surface of said voice coil and a radial inside surface of said magnetic structure when an annular magnet defines a portion of a wall of said magnetic structure.

10. The audio speaker of claim 1 wherein said one side of said voice coil is between an inside surface of said voice coil and said central magnetic post when a permanent magnet defines a portion of said central magnetic post.

11. A method of assembling a vibration system to a driver unit of an audio speaker, said method comprising: disposing a predetermined amount of a magnetic fluid only on one side of a voice coil positioned in an annular gap of a driver unit wherein said one side has a higher magnetic flux density than the opposite side of said voice coil, said voice coil being configured to prevent said magnetic fluid from migrating to the other side of said voice coil;aligning said vibration system with said driver unit wherein said voice coil of said vibration system is movably mounted into said annular gap; andfixing said vibration system to said driver unit.

12. The method of claim 11 further comprising obtaining a magnetic fluid having a magnetization in the range of about 100 to about 600 Gauss.

13. The method of claim 12 further comprising obtaining a magnetic fluid having a magnetization in the range of about 200 to about 500 Gauss.

14. The method of claim 13 wherein said magnetic fluid obtaining step includes selecting a magnetic fluid having a magnetization in the range of about 300 to about 400 Gauss.

15. The method of claim 11 wherein said magnetic fluid obtaining step includes selecting a magnetic fluid having a higher magnetization when said audio speaker has a voice coil with higher excursion and lower magnetic field.

16. The method of claim 11 wherein said magnetic fluid obtaining step includes selecting a magnetic fluid having a lower magnetization when said audio speaker has a voice coil with lower excursion and higher magnetic field.

17. The method of claim 11 further comprising forming said voice coil with a tubular form of sufficient length to prevent migration of said magnetic fluid at a distal end of said voice coil from said one side of said voice coil having a higher magnetic flux density to a second side of said voice coil having a lower magnetic flux density.

18. The method of claim 11 further comprising forming said voice coil having vent openings positioned sufficiently distant from said magnetic fluid to prevent migration of said magnetic fluid during oscillation of said voice coil.