WO2001035698A1

WO2001035698A1 - Flat speaker

Info

Publication number: WO2001035698A1
Application number: PCT/IB1999/002102
Authority: WO
Inventors: Wah Yung Tsoi
Original assignee: M-Tech (Hk) Co. Ltd.
Priority date: 1999-11-10
Filing date: 1999-11-10
Publication date: 2001-05-17
Also published as: JP2003514471A

Abstract

The invention is applicable on multi and all loudspeakers related application. A loudspeaker with at least one diaphragm which can be vibrated to radiate sound from at least one face, with at least one or more driver unit operable by a varying electric current to generate a varying force on the membrane or diaphragm. The force varies to the electric current. The diaphragm has the circular hole or holes on one or serveral position which the driver unit or units can fit into it and mounted with adhesive.

Description

FLAT SPEAKER

A flat speaker is a speaker which use a relative flat driver compare to the traditional cone shape driver. The flat driver is a circular or elliptical driver and has a diaphragm

Al made of driver paper or layers of EVA - EPS, PVC or PU.

Although the example here is circular, the diaphragm can be rectangular or polymorphous. The diaphragm is vibrated by a driver unit A7 which comprises a magnet A5, a voice coil A4 and a membrane A6. The ma^tτnet A5 is mounted on the rear panel A8 and the voice coil A4 is mounted on the main diaphragm Al. The edge of the diaphragm Al is mounted at the frame of the rear panel A8. The wiring A2 of the voice coil A4 is fasten on the rear panel A8 on the clip A3.

FIELD OF THE INVENTION

The invention we claimed is related to loudspeakers with the thickness less than 4 cm. The invention is applicable on multi media and all loudspeakers related applications, including hi fi system, television and car stereo. This invention can also apply on the driver making process to produce a relative flat with high quality performance.

BACKGROUND

The flat speakers have been around for many years. 1880-1920 for use in the theatre organs. These electro-static membrane, electro-magnetic planar drives have large volume that create the problem in modern entertainment systems. They have had a less than desirable sound frequency response and sound distribution pattern. Our approach is based on the modern cone driver (Bell labs 1923, RCA 1925) to produce a low cost, good sound quality and scalable flat speakers.

STATEMENT OF THE INVENTION The aspect of the invention is provided a loudspeaker which is relative flat compare to the traditional cone shape speaker. The flat loudspeaker have a planer membrane or diaphragm that can vibrated to radiate sound from its surfaces. The panel material can be traditional speaker paper or the material that have a semi-elastic nature like PNC,PU, EVA, EPS and PP.The traditional cone shape driver unit operable by a varying electric current to generate a varying force on the cone shape membrane. The force varying in a manner related to the varying electric current, characterized by the driver unit being connected to the membrane at central positions or mounted to structure which is in turn connected to the membrane at one or more selected positions. The flat driver will follow the idea of using a combination of voice coil and magnet to produce the driven force for the panel. The diaphragm we used is flat compare to the traditional cone shape structure.

The diaphragm material we prefer will have a bending strength in one direction of the plane of the material which is significantly greater than the bending strength along a line in the plane of the material at right angles to the first direction.

The diaphragm we prefer has a longitudinal bending strength which is more than twice of its transverse bending strength.

Normally, the driver unit is located at the center of the diaphragm. It can be located remote from the fame or outside from the frame. The driver unit is connected to the diaphragm whereby the driver unit will apply varying force, corresponding to the varying electric current and cause the diaphragm to flex and emit a signal from the face of the membrane exterior of the loudspeaker.

The driver unit is mounted to the diaphragm at said one or more selected positions which is remote from the edge of the diaphragm. The positions are selected so that flexure of the membrane in one or more of its natural modes of vibration is not impeded. The position we prefer is at the center or around the central part of the membrane.

The diaphragm is approximately 500 GSM(gram per square meter) or less, and should have the hardness of 50 or more.

The diaphragm can be flat or slightly cone shape as shown in Fig 4. Alternatively, the membrane can be a sandwich layer as shown in figure 3 with the total thickness of around 3-5 mm.

The loudspeaker as designed may be a sealed box, with or without one or more ports or vents provided through the frame or through the diaphragm. It can also be a total openness structure as shown in figure 6 or a bi-planar structure as in figure 7 ,

The diaphragm is made of a sheet of (with slightly cone shape) of extruded paper material. It can also be made from different layers of material adhesive together to form a combination of frequency response. The preferable material for this combination is PVC, PU, PP, EVA and EPS. We call this as the sandwich structure. The driver unit includes a magnet, one pole of which is in magnetic continuity with a yoke and the other pole of which is positioned from the yoke by an air gap through which gap a voice coil is operable, the voice coil being attached to drive and the diaphragm. Some sort of damping material, which is probably cloth or cotton fiber, can be put inside the rear panel to allow the passage of air through the vents. This damping material will also prevent any dirt from entering the panel. BRIEF DESCRIPTION OF THE DRAWING

One embodiment of the invention is described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a front view of a loudspeaker according to the invention,

Figure 2 is a cross-section in a vertical plane along the line I-I in Figure 1 ,

Figure 3 is a partial perspective view of the diaphragm (sandwich structure) of the loudspeaker, Figure 4 is a partial perspective view of the diaphragm (cone structure) of the loudspeaker of another design,

Figure 5 is a cross-section of a further embodiment,

Figure 6 is a cross-section of another embodiment.

Figure 7 is a cross-section of another embodiment. Figure 8 is a first rear view of the embodiment shown in Figure 5, and

Figure 9 is a second modified rear view of the component shown in Figure 5,

Figure 10 is a side view of a voice coil shown in section in Figure 2.

Figure 11 is a side view of the magnet shown in section in Figure 2.

EXAMPLE 1

In figure 1. we can see a circular design for the flat panel. Basically, the panel can be any shape. It can be rectangular, polymorphous or elliptical. A flat loudspeaker A includes a circular peripheral frame A9 conveniently made of ABS plastic board. The frame is suspended by wire of cords A2 attached to loops or other fasteners A3 at the top of the frame A9.

In Figure 2, the front of the loudspeaker A is covered by a front diaphragm Al which is attached and sealed around the edges thereof by a suitable adhesive to the front face of the frame A9. The rear of the loudspeaker A is covered by a rear panel A8 of which are directly connected to the frame A9. Thus the interior of the loudspeaker A constitute a sealed box.

A driver unit is positioned adjacent the center of the diaphragms Al. The driver unit is the same as to those used in conventional cone-type loudspeakers and includes a magnet A5, which can be a permanent magnet or an electromagnet, and a voice coil A4. The voice coil A4 carries the usual winding connected by leads A2 to terminals A3 on the rear of the loudspeaker A.

The magnet A5 is fastened, for example, by an adhesive to the interior surface of the rear panel A8 and the voice coil A4 is fastened to the frame A10 which hold the magnet A5 on position by the spider A6. The spider A6 allows the voice coil A4 to position and vibrate inside the gap of the magnet A5.

The voice coil A4 is also connected to the interior surface of the front diaphragm Al. The dimensions of the driver and the spacing of the front diaphragm Al and rear panel A8, are arranged so that the voice coil A4 is in the correct operative position relative to the magnet A5, and properly centered therein. The dust cover A7 is also added on top of the voice coil A4 to prevent any dirt to get into the magnet gap A5.

The shape of the diaphragm Al may be slightly coned like the traditional drivers. It can also be flat and instead of being flat, it could be corrugated or sandwich like so as to provide a modified acoustic performance of the loudspeaker A. EXAMPLE 2

Figure 3 shows a preferred construction for the diaphragm Al . Although the diaphragm is circular, it can be any shape. The diaphragm shown here has a sandwich like structure and made from more than two layers. The combination of the layer material should have different density with a total density less than 500 GSM. The panel should be around 2 to 5 mm thick. Preferably the EVA layer (Bl) , the EPS layer (B2) and PVC layer (B3) stick together with adhesive are one of the combination we can used in constructing panel. The EVA has the better response to low frequency vibration. The EPC has better performance in middle frequency vibration. The PVC material gives better result in high. The combination of all to form a sandwich like structure gives a good performance for flat panel.

This structure can be modified to have two layers with combination of more than three materials. The base layer is made by PVC. The face layer will be the combination of EVA and EPS pieces to achieve different sound response.

Figure 4 shows a modified construction for the front diaphragm Al from the original cone shape driver. It comprises a circular cone shape paper (which is slightly cone shaped to give a relatively flat surface). It contains a circular hole at the center A21 to hold the voice coil A4 in position. The outer edge of the diaphragm is made by a spider A20 to attach to the frame A9 on speaker A.

EXAMPLE 3

In figure 5, we can see a modified version from the design of speaker A. The speaker C has a rectangular panel. Basically, the panel can be any shape. The loudspeaker C has a rectangular diaphragm Cl. Instead of a cone shape design, the diaphragm Cl is flat. The internal structure a very similar to speaker A except the dust cover C2 is a concave shape facing inward to the magnet.

EXAMPLE 4

In figure 6, the loudspeaker D is covered by a front diaphragm Dl which is attached and sealed around the edges of the frame D3. The other end of the frame is attached to the rear diaphragm D2 instead. There is no rear panel in the loudspeaker D. Thus the interior of the loudspeaker D constitute a sealed box made by the wall of the diaphraem. Both diaphragm Dl and D2 will vibrate together to radiate sound from its surfaces. The rear diaphragm will connect to the magnet D4. The voice coil D5 is positioned at the center of the front diaphragm Dl with a dust cover D7.

EXAMPLE 5

Figure 7 shows an openness design of the flat driver E. In the design, we use only one diaphragm El which connect to the frame E2. The magnet E3 is also connected to the frame E3 to create an openness structure to the driver speaker. The voice coil E4 is attached to magnet E3 by the spider E4. The voice coil E4 is positioned at the center of the diaphragm El on the circular hole E7. It is covered by the dust cover E6 to avoid the dust to get into magnet E3. The diaphragm radiate sound from front and rear face of the surface in this example. EXAMPLE 6

Figures 8 and 9 are the possible design for the rear panel in figure 5. Figure 8 contains an array of gaps CIO. The sizes and locations of the gaps CIO are carefully chosen to achieve a smooth frequency response from the loudspeaker C. Alternative, or additional modification of the frequency response curve is achieved by adding some damping material on the rear panel as shown in figure 9. The damping material will absorb the vibration and give a better sound quality on base.

Figure 10 shows the possible structure of the voice coil that can be used. The voice coil could be single layer (linear layer) or double layer (non-linear) as shown in the figure. These kind of voice coils are commonly used in the traditional cone shape speaker drivers.

Figure 11 shows the magnet system uses in the flat panels. The magnet used here is a common magnet used in the cone shape speaker driver. It contains three major parts. The pole piece is made from the material low carbon mild steel. The magnet is made from neodymium. The magnet cup is made from the material low carbon mild steel. The thickness of the magnet gap should be adjusted to achieve the maximum magnetic field power to drive the voice coil.

Claims

WHAT WE CLAIM IS

1. A loudspeaker with at least one diaphragm which can be vibrated to radiate sound from at least one face, with at least one or more driver unit operable by a varying electric current to generate a varying force on the membrane or diaphragm.

The force varies to the electric current. The diaphragm has the circular hole or holes on one or several position which the driver unit or units can fit into it and mounted with adhesive.

2. A loudspeaker as claimed in claim 1 characterized by connecting to the peripheral frame, which is connected to a plastic panel at rear. Alternatively, the front diaphragm of the loudspeaker as claimed in claim 1 is connect to a frame where is connected to a rear diaphragm.

3. A loudspeaker as claimed in claim 2, characterized by the driver unit being connected to both of said diaphragms whereby the driver unit will apply varying force, corresponding to the varying electric current, to said diaphragms and cause the diaphragm to flex and emit an acoustic signal from the face of the diaphragm exterior and interior of the loudspeaker.

4. A loudspeaker as claimed in claim 1, characterized in that said the diaphragm is made of common speaker paper with or without spider at the edges.

5. A loudspeaker as claimed in claim 1, characterized in that said the diaphragm is made of combination of layers with different density of material.

6. A loudspeaker as claimed in claim 1, characterized in that said the diaphragm is made of a sandwich diaphragm or sandwich membrane . A sandwich diaphragm or sandwich membrane is a diaphragm of which has at least two or more layers and with a structure which contains at least two different material with different density and tensile strength combine together.

7. A diaphragm as claimed in claim 6, make by the material of PVC, EVA, EPS , PU and PP plastic.

8. A loudspeaker as claimed in claim 1, characterized in that said the diaphragm is flat or a slightly cone shaped with a least one circular hole in it to hold the driver.

9. A loudspeaker as claimed in any preceding claim characterized in that each diaphragm is less than 500 GSM.

10. A loudspeaker as claimed in any preceding claim characterized in that each diaphragm has a tensile strength more than 20 MPa.

11. A loudspeaker as claimed in any preceding claim characterized in that each diaphragm has a hardness of 50 or more.

12. A loudspeaker as claimed in any preceding claim characterized in that the driver unit includes one voice coil, which fastened to a circular hole of the diaphragm with a dust cover on top.

13. A loudspeaker as claimed in any preceding ciaim characterized in that the driver unit includes at least one magnet, which fastened to a structure of rear panel or rear diaphragm. That structure can be attached to the voice coil as claim in claim 12 by a spider adhesive to the voice coil and the structure itself.

14. A magnet unit as claimed in claim 13 with one pole of which is in magnetic continuity with a yoke and the other pole of which is positioned from the yoke by an air gap through which gap a voice coil is operable, the voice coil being attached to drive the diaphragm, characterized in that the yoke is made from low oxygen pure iron annealed very slowly in hydrogen.

15. A loudspeaker as claimed in claim 1 characterized in that the voice coil can be linear with uniform turns per winding trough the voice coil. The voice coil can also be non-linear of which has more windings per unit length thereof away from that axial part of the voice coil which is in said air gap when no electric current is passed through the windings.

16. A voice coil as claimed in claim 15 characterized in that the voice coil winding is a single layer or double layer, with the windings spaced apart in the region of said axial pair.

17. A loudspeaker as claimed in claim 1 characterized in that a sheet of damping material is connected from a stationary part of the loudspeaker to said part of the diaphragm adjacent the panel or to the panel and in which the damping material is cloth so as to allow the passage of air through.

18. A loudspeaker substantially as herein described with reference to any one of the accompanying drawings.