Coaxial loudspeaker arrangement

1. Coaxial loudspeaker arrangement with an outer diaphragm ( 21 ) for operating in a lower frequency range, an inner diaphragm ( 23 ) for operating in a higher frequency range, both located in a common loudspeaker frame ( 10 ), with an outer voice coil ( 22 ) connected to the outer diaphragm ( 21 ), an inner voice coil ( 24 ) connected to the inner diaphragm ( 23 ), two coaxially arranged magnets ( 31 , 32 ), and ferrite cores ( 41 , 42 , 43 ) in association with the magnets, wherein the voice coils ( 22 , 24 ) extend into air gaps ( 51 , 52 ) between the ferrite cores, and the diaphragms are connected to the loudspeaker frame ( 10 ) through flexible suspending elements ( 12 - 14 ), characterised in that an inner core ( 41 ) and an outer core ( 42 ) separated from each other by an inner air gap ( 52 ), are located between an outer magnet ( 31 ) and an inner magnet ( 32 ); one ferrite core ( 43 a ) of the outer magnet ( 31 ) is separated by an outer air gap ( 51 ) from the outer core ( 42 ) located between the two magnets, wherein the voice coil ( 22 ) of the outer diaphragm ( 21 ) extends into the outer air gap ( 51 ) and the voice coil ( 24 ) of the inner diaphragm ( 23 ) extends into the inner air gap ( 52 ).

2. The loudspeaker arrangement of claim 1 , characterised in that at least a part of the inner magnet ( 32 ) and at least a part of the outer magnet ( 31 ) is located in the same plane.

3. The loudspeaker arrangement of claim 2 , characterised in that the upper plane surface of the inner magnet ( 32 ) is located in proximity of the upper plane surface of the outer magnet ( 31 ), above the upper plane surface of the outer magnet ( 31 ), and the lower plane surface of the inner magnet ( 32 ) is located between the upper plane surface and the lower plane surface of the outer magnet ( 31 ).

4. The loudspeaker arrangement of claim 1 , characterised in that the outer magnet ( 31 ) is located between a lower and an upper ferrite core ( 43 a , 43 b ), wherein the outer diameter of the two ferrite cores ( 43 a , 43 b ) is essentially equal to the outer dimension of the outer magnet ( 31 ) and the dimension of the air gap ( 51 ) between the inner diameter of the upper ferrite core ( 43 a ) and the outer diameter of the outer ferrite core ( 42 ) is selected in accordance with the dimension of the outer voice coil ( 22 ).

5. The loudspeaker arrangement of claim 1 , characterised in that the upper plain surface of the outer ferrite core ( 42 ) is located substantially in the same plane as the upper plane surface of the upper ferrite core ( 43 a ), and the upper plane surface of the inner ferrite core ( 41 ) is located in proximity of the upper plane surface of the outer ferrite core ( 42 ), below the upper plane surface of the outer ferrite core ( 42 ).

6. The loudspeaker arrangement of claim 1 , characterised in that the outer ferrite core ( 42 ) comprises a head portion adjacent to the inner voice coil ( 24 ), and a foot portion fitting to the inner ferrite core ( 41 ), wherein the dimension of the air gap ( 52 ) between the inner diameter of the head portion of the outer ferrite core ( 42 ) and the outer diameter of the inner ferrite core ( 41 ) is selected in accordance with the dimension of the inner voice coil ( 24 ).

7. The loudspeaker arrangement of claim 6 , characterised in that a hollow middle portion is formed between the head portion and the foot portion of the outer ferrite core ( 42 ), and the head portion comprises a conical surface extending from a higher outer wall to a lower inner wall.

8. The loudspeaker arrangement of claim 1 , characterised in that the inner ferrite core ( 41 ) has a substantially cylindrical shape with a recess in the upper part for receiving the inner magnet ( 32 ).

9. The loudspeaker arrangement of claim 8 , characterised in that the upper plane surface of the inner ferrite core ( 41 ) is located higher than the upper plane surface of the inner magnet ( 32 ), thus the inner magnet ( 32 ) inserted into the inner ferrite core ( 41 ) is covered by a ferrite core ( 44 ) having the shape of a circular disc and fitting within the recess of the inner ferrite core ( 41 ).

10. The loudspeaker arrangement of claim 8 , characterised in that in the lower region of the outer surface of the inner ferrite core ( 41 ) a circumferential recess is formed to mate with the inner edge of the lower ferrite core ( 43 b ).

11. The loudspeaker arrangement of claim 1 , characterised in that the north pole and the south pole of the outer magnet ( 31 ) are directed towards the upper and lower ferrite core ( 43 a , 43 b ).

12. The loudspeaker arrangement of claim 1 , characterised in that the north pole and the south pole of the inner magnet ( 32 ) are directed inwardly and outwardly, respectively, and the outwardly directed pole of the inner magnet ( 32 ), is identical with the pole of the outer magnet ( 31 ) which is directed to the upper ferrite core ( 43 a ).

13. The loudspeaker arrangement of claim 1 , characterised in that at least one of the voice coils ( 22 , 24 ) has a multilayered coil, wherein the number of layers above each other is variable along the coil.

14. The loudspeaker arrangement of claim 13 , characterised in that at least one of the voice coils ( 22 , 24 ) has a substantially conical shape, with more windings above each other on the diaphragm side, and less windings on the other side opposite the diaphragm.

15. The loudspeaker arrangement of claim 1 , characterised in that the material used for the magnets is neodymium or it comprises neodymium.