PURPOSE: To prevent the invasion of dusts without interfering the radiation of sound waves from a diaphragm, by fabricating an external case with a very thin plate member formed with a number of minute holes.
CONSTITUTION: A front protecting member 31 and a rear protective member 32 of an external case 1 are constituted with a very thin plate member formed with a number of minute holes 35. The minute holes 35 are through-holes of hexagonal shape having about 0.2mm diameter, and to avoid the interference of radiation of sound waves, when an electroacoustic transducing element 10 is covered, electroforming or etching is made for a part opposing to a diaphragm 15 in case of a front protective member 31, and for a part opposing to through-holes 23, 25 provided at a magnetic circuit 14 in case of a rear protective member 32. Then, since the external case 1 is formed with a very thin plate, it can be very low acoustic impednace and a small load to a reproduced sound radiated from the diaphragm 15, further allowing to prevent the invasion of dusts due to very minute holes.
| JP2000156895 | STRUCTURE OF SPEAKER BOX |
WATANABE SHINGO
TOUNO KOUJI
| JPS5352444U | 1978-05-04 | |||
| JPS5118195A | 1976-02-13 | |||
| JPS5315421A | 1978-02-13 | |||
| JPS5249374A | 1977-04-20 | |||
| JPS467561Y1 | 1971-03-17 | |||
| JPS4727927U | 1972-11-29 |
| US2391924A | 1946-01-01 |