Loudspeaker having pole piece with integral vent bores

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS.
1-8, alternative embodiments of a loudspeaker 10 are illustrated which incorporate essentially the same structure, except for variations in the means for cooling the voice coil 32 described in detail below.
For purposes of the present discussion, the overall construction of the speaker 10 is described with reference to FIG.
1, it being understood that such description applies to FIGS.
3-8.
Additionally, FIG.
2 is provided to depict a cross sectional perspective view of the pole piece 30 of FIG.
1, particularly the vent bores therein, and it should be understood that the pole pieces of the other embodiments have similar vent bores, as described below.
The speaker 10 generally comprises a motor structure 12, a frame 14 mounted to the motor structure 12, a diaphragm 16, a lower suspension or spider 18 and an upper suspension or surround 20.
Conventionally, the motor structure 12 includes a top plate 22 and a back plate 24 which are spaced from one another and mount a permanent magnet 26 therebetween.
A pole piece 30 is integrally formed with and extends upwardly from the back plate 24 into a central bore 28 formed in both the magnet 26 and top plate 22.
An air gap 29 is formed between the top plate 22 and the pole piece 30, as shown.
A voice coil 32 is also provided which includes a hollow, cylindrical-shaped former 34, having an inner surface 35 and an outer surface 37 which receives a wire winding 36.
The former 34 is concentrically disposed about the pole piece 30, and the voice coil 32 is axially movable within the air gap 29 during operation of the speaker 10.
The voice coil 32 is held in place with respect to the pole piece 30 by the diaphragm 16, spider 18 and surround 20.
One end of the diaphragm 16 is affixed to the former 34 by adhesive or the like, and its opposite end connects to the surround 20.
The surround 20, in turn, is mounted to the upper end 38 of the frame 14 as shown.
The diaphragm 16 and surround 20 collectively provide support for the voice coil 32, in addition to the lower suspension or spider 18