Audio driver and method for transforming an electrical signal into air movement

• US 9,565,498 B2
• Filed: 12/06/2013
• Issued: 02/07/2017
• Est. Priority Date: 12/06/2013
• Status: Active Grant

• Current Assignee: Jens Waale
• Original Assignee: Jens Waale
• Inventors: Waale, Jens
• Primary Examiner(s): Nguyen, Duc
• Assistant Examiner(s): Mohammed, Assad
• Application Number:
  US14/098,932
• Publication Number:
  US 20140112504A1
• Time in Patent Office: 1,159 Days
• US Class Current: 1/1
• 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

An electromagnetic transducer for sound and ultrasound reproduction includes a substantially flat coil coupled to a diaphragm that is near to and facing the North or South side of a magnet. A very thin membrane made from a non-magnetic but electrically conductive material is independently mounted from the diaphragm and faces it. An AC signal in the coil results in diaphragm movement and “modulates” the permanent 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 generate sound and result in an unusually flat SPL/frequency response, with unusually low narrow-band intensity variation and very low distortion. The transducer is also unique among electromagnetic transducers in that the force acting on the membrane is uniformly distributed over much of it, as in an electrostatic sound transducer.

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 an electrically insulating, non-magnetic material;

a coil comprising a substantially flat planar arrangement of an electrically conductive material, wherein the coil is disposed on the first movable surface and the first movable surface is directly driven thereby;

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

a second movable surface spaced apart from the first movable surface by a second gap, wherein the second movable surface comprises an electrically conductive, non-magnetic material, and wherein;

(a) the second movable surface is not directly driven;

(b) the second gap is not sealed; and

(c) the air movement results from movement of the first movable surface and the second movable surface.

2. The apparatus of claim 1 wherein the first movable surface and the second movable surface are suspended independently from one another and are not physically coupled to one another.

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:

(a) the first movable surface has a first end and a second end;

(b) the second movable surface has a first end proximal to the first end of the first movable surface and a second end proximal to the second end of the second movable surface;

(c) the second gap has a first size proximal to the first end of the first and second movable surfaces and a second size proximal to the second end of the first and second movable surfaces; and

(d) the second movable surface diverges from the first movable surface such that the first size of the second gap is different from the second size of the second gap.

5. The apparatus of claim 4 wherein the second movable surface diverges from the first movable surface non-linearly.

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 and the second movable surface is not parallel to the first movable surface, the second gap having a non-uniform size and a monotonic profile.

8. The apparatus of claim 1 wherein the second surface is a foil and comprises, as a major component, aluminum.

9. The apparatus of claim 1 wherein the second movable surface comprises a physical adaptation for preventing standing waves.

10. The apparatus of claim 1 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.

11. The apparatus of claim 10 and further comprising a second driver, wherein the second driver is a dynamic driver.

21. The apparatus of claim 1 wherein relative contributions of the first movable surface and the second movable surface to the air movement generated thereby varies as a function of frequency of the electrical signal and as a function of distance between the first movable surface and the second movable surface.

22. The apparatus of claim 21 wherein, when operating as a tweeter for reproducing, as sound, frequencies of the electrical signal in a range between about 2 kHz and 20 kHz:

at relatively lower frequencies of the electrical signal, movement of the first movable membrane causes relatively more of the air movement than movement of the second movable membrane; and

at relatively higher frequencies of the electrical signal, movement of the second movable membrane causes relatively more of the air movement than movement of the first movable membrane.

23. 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 and the second movable surface is parallel to the first movable surface such that the second gap has a uniform size.

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;

(a) a first gap is defined between the magnet and the first surface;

(b) a second gap is defined between the first surface and the second surface;

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

(d) the first surface comprises an electrically insulating material, has an electrically conductive coil comprising a substantially flat planar arrangement of one more wires disposed thereon, and is directly driven to movement by an electrical signal during operation of the driver, wherein the movement results from an electromagnetic interaction between a magnetic field of the magnet and a magnetic field generated by the electrical signal flowing through the electrically conductive coil;

(e) the second surface, which comprises an electrically conductive, non-magnetic material, is not directly driven; and

(f) when the driver is in a quiescent state, the first surface is substantially parallel to a facing surface of the magnet such that the first gap has a uniform size and the second surface is not parallel to the first surface, the second gap having a non-uniform size that tapers monotonically.

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 wherein the first surface is a flat planar surface consisting essentially of a material selected from the group consisting of a plastic and a cellulosic material.

15. The apparatus of claim 13 wherein the electrically conductive coil is disposed on a side of the first surface that faces the magnet.

16. The apparatus of claim 12 wherein when the driver is in the quiescent state:

(a) a size of the first gap is greater than a first size of the second gap near a first end thereof;

(b) the size of the first gap is smaller than a second size of the second gap near a second end thereof.

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 wherein the taper 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 substantially flat planar 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, wherein there is a gap between a source of the non-varying magnetic field and the first surface; 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, wherein the air movement results from;

(a) movement of the first surface, due to interaction of the of the varying magnetic field with the non-varying magnetic field; and

(b) movement of the second surface, due, at least in part, from interaction of a magnetic field generated by the eddy currents with the non-varying magnetic field and the varying magnetic field.