FIG. 5 is a sectional view showing a conventional speaker module. Magnet 2 is sandwiched between upper plate 3 and yoke 1, so that inner magnet type magnetic circuit 4 is formed. Frame 8 is connected with yoke 1. First diaphragm 7 is bonded to a circumference of frame 8, and voice coil 6 connected with first diaphragm 7 is inserted into magnetic gap 5 of magnetic circuit 4. Thus, a speaker unit is constructed.
Panel 10 is connected with frame 8, and first diaphragm 7 is surrounded by panel 10 which is a part of a wall constructing hermetic space 12. Second diaphragm 11 is connected with panel 10, so that first diaphragm 7 and second diaphragm 11 are acoustically coupled with each other. Thus, speaker module 13 is constructed. This kind of speaker module is, for example, disclosed in Unexamined Japanese Patent Publication No. 2003-179988.
However, speaker module 13 is extremely difficult to be designed suitable for an electric device or an apparatus using it. Speaker module 13 is designed in such a manner that its outward appearance is substantially plane because the device, in which speaker module 13 is installed, is required to be thin, small and compact. Therefore, second diaphragm 11 has a plane shape. When second diaphragm 11 is designed, for example, a photograph or a picture is printed on a surface of second diaphragm 11. In this case, contents of the photograph or the picture are fixed, so that it does not make a high impact on a user.
In a case where the device, in which speaker module 13 is installed, has a display function such as liquid crystal, panel 10 and second diaphragm 11 are structured with transparent material. Then, a display section such as liquid crystal is placed under them, and speaker module 13 is installed in the electric device with second diaphragm 11 designed nothing. In this case, because panel 10 and second diaphragm 11 are transparent, speaker module 13 can not appeal its existence.