AUDIO DRIVER AND METHOD FOR TRANSFORMING AN ELECTRICAL SIGNAL INTO AIR MOVEMENT

• US 20140112504A1
• Filed: 12/06/2013
• Published: 04/24/2014
• Est. Priority Date: 12/06/2013
• Status: Active Grant

• Current Assignee: Jens Waale
• Original Assignee: Jens Waale
• Inventors: Waale, Jens
• Granted Patent: US 9,565,498 B2
• Time in Patent Office: Days
• US Class Current: 381/152
• CPC Class Codes: H04R 1/288 for loudspeaker transducers
• CPC Class Codes: H04R 2209/041 Voice coil arrangements comprising more than one voice coil unit on the same bobbin
• CPC Class Codes: H04R 7/08 comprising superposed layers separated by air or other fluid
• CPC Class Codes: H04R 9/025 Magnetic circuit
• CPC Class Codes: H04R 9/048 of the ribbon type

Abstract

A variant of a planar magnetic transducer for sound and ultrasound reproduction includes a substantially flat coil fixed on a diaphragm. A source of a non-varying magnetic field is disposed on one side of the diaphragm; a thin, electrically conductive, non-magnetic membrane is disposed on the other side. An AC signal in the coil results in diaphragm movement and modulation of the non-varying magnetic field. The modulating field generates a current in the membrane, which, upon further interactions, causes the membrane to move. The two independently moving surfaces, each of which produce sound, together result in an unusually flat SPL/frequency response, with very low narrow-band intensity variation and distortion. The forces acting on the moving planes are substantially uniformly distributed on active parts and the force per unit area is high. In embodiments directed to reproducing sound in a limited frequency band, the driver can be very efficient.

Claims

1. An apparatus including a first driver that transforms an electrical signal into air movement, wherein the first driver comprises:

a source of a non-varying magnetic field;

a first movable surface, wherein the first movable surface comprises a first material;

a first gap between the source of a non-varying magnetic field and the first movable surface;

a second movable surface, wherein the second movable surface comprises a second material, and wherein the first material is different than the second material; and

a second gap between the first movable surface and the second movable surface.

2. The apparatus of claim 1 wherein the first driver further comprises a coil of electrically conductive material, and wherein the coil comprises a substantially flat planar arrangement of one or more wires, and further wherein the coil is disposed on the first movable surface.

3. The apparatus of claim 1 and further wherein the first movable surface is a flat planar surface.

4. The apparatus of claim 1 and further wherein the second movable surface is a flat planar surface.

5. The apparatus of claim 1 and further wherein the second material is electrically conductive and non-magnetic.

6. The apparatus of claim 1 and further wherein the first movable surface is disposed between the source of the non-varying magnetic field and the second movable surface.

7. The apparatus of claim 1 wherein the source of the non-varying magnetic field is a permanent magnet, and further wherein, when the first driver is in a quiescent state, the first movable surface is substantially parallel to a facing surface of the permanent magnet such that the first gap has a uniform size.

9. The apparatus of claim 2 and further wherein the first movable surface is directly driven via the coil and the second movable surface is not directly driven.

10. The apparatus of claim 2 and further comprising:

an enclosure, wherein the first driver is disposed at least partially in the enclosure; and

speaker terminals, wherein the speaker terminals are accessible at an exterior of the enclosure to electrically couple to speaker wire that delivers an electrical signal thereto, and further wherein the speaker terminals are electrically coupled to the coil of the first driver.

8. The apparatus of claim 8 and further wherein, when the first driver is in a quiescent state, the second movable surface is not parallel to the first movable surface such that the second gap has a non-uniform size.

11. The apparatus of claim 11 and further comprising a second driver, wherein the second driver is a dynamic driver.

12. An apparatus including a driver that transforms an electrical signal into air movement, wherein the driver comprises:

a magnet; and

a first surface and a second surface, wherein;

(i) the first surface and the second surface are movable;

(ii) the first surface has an electrically conductive coil comprising a substantially flat planar arrangement of one more wires disposed thereon and is directly driven by an electrical signal during operation of the driver; and

(iii) the second surface, which comprises an electrically conductive, non-magnetic material, is not directly driven.

13. The apparatus of claim 12 wherein the first surface and the second surface are disposed on a first side of the magnet.

14. The apparatus of claim 12 and further wherein the first movable surface is a flat planar surface.

15. The apparatus of claim 14 and further wherein the second movable surface is a flat planar surface.

16. The apparatus of claim 15 wherein the magnet is a permanent magnet and further wherein a major surface of the permanent magnet faces the first surface, and further wherein:

(i) the major surface and the first surface are substantially parallel to one another; and

(ii) the major surface and the second surface are not parallel to one another.

17. The apparatus of claim 12 and further wherein the second surface is a foil consisting essentially of aluminum.

18. The apparatus of claim 12 and further wherein the second surface is a foil and comprises, as a major component, aluminum, and as a minor component, copper.

19. The apparatus of claim 12 further comprising a gap between the first surface and the second surface, wherein a size of the gap varies and wherein the variation in the size of the gap is non-linear.

20. A method for transforming an electrical signal into air movement, the method comprising:

generating a varying magnetic field by passing a varying electrical current through a coil of wire disposed on a first surface, wherein the first surface is not electrically conductive and is non-magnetic;

interacting the varying magnetic field with a non-varying magnetic field; and

generating eddy currents in a second surface by exposing the second surface, which is electrically conductive and non-magnetic, to the non-varying magnetic field as modulated by the varying magnetic field.