Electro-acoustic transducer including a miniature voice coil
A tool for arranging voice coil leadouts in a microspeaker comprises an expanding collet constructed and arranged for positioning at an interior of a bobbin having an inner diameter, the expanding collet including a hole that extends through an interior in a longitudinal direction of the expanding collet; a center pin extending through the hole of the expanding collet, the expanding collet applying a force against the inner diameter of the bobbin in response to a position of the center pin in the hole of the expanding collet relative to the interior of the expanding collet; and a forming mandrel including a hole that extends through an interior in a longitudinal direction of the forming mandrel. The expanding collet extends through the hole in, and coaxial with, the forming mandrel. The expanding collet rotates the bobbin about the longitudinal direction of the expanding collet relative to the forming mandrel to form helical leadout regions of a voice coil about the bobbin.
1. An electro-acoustic transducer, comprising:
a sleeve;
a diaphragm at a first end of the sleeve;
a bobbin coupled to the diaphragm at an interior of the sleeve;
a voice coil about the bobbin, the voice coil having a first helical leadout region and a second helical leadout region, the first and second helical leadout regions each including:
a bend portion extending tangentially away from a main body of the voice coil;
a helix portion that extends 180 degrees about an inner diameter of the sleeve from the main body to the bend portion; and
a straight portion extending at an angle from the bend portion.
2. The electro-acoustic transducer of claim 1 , further comprising a circuit board at a second end of the sleeve opposite the first end, the circuit board including contact pads to which ends of the straight portions of the first helical leadout region and a second helical leadout region are coupled.
3. The electro-acoustic transducer of claim 1 , wherein the bend portion of the first helical leadout region extends away from the bobbin and the main body of the voice coil to the straight portion of the first helical leadout region along a first recess of the sleeve in a direction away from the diaphragm, and wherein the bend portion of the second helical leadout region extends away from the bobbin and the main body of the voice coil to the straight portion of the second helical leadout region along a second recess of the sleeve in a direction away from the diaphragm.
4. The electro-acoustic transducer of claim 1 , wherein the helix portion of each of the first and second helical leadout regions is suspended in a space between the voice coil and the inner diameter of the sleeve.
5. The electro-acoustic transducer of claim 1 , further comprising a guide insert about the bobbin in the sleeve, the guide insert including a grooved element that extends along a length of the sleeve, the straight portion of at least one of the first and second helical leadout regions extending through the grooved element.
6. The electro-acoustic transducer of claim 5 , wherein the grooved element includes a rounded edge about which the bend portion of the of at least one of the first and second helical leadout regions is coupled.
7. The electro-acoustic transducer of claim 5 , further comprising a back plate coupled to the bobbin at a second end of the sleeve opposite the first end, the guide insert providing a positive stop for the back plate.
8. The electro-acoustic transducer of claim 5 , wherein the guide insert includes a guide portion that extends to an opening at a second end of the sleeve opposite the first end and includes the grooved element.
9. A voice coil assembly of an electro-acoustic transducer, comprising:
a main body;
a first leadout region including:
a first bend portion extending tangentially away from the main body;
a first helix portion that extends 180 degrees about an inner diameter of the electro-acoustic transducer from the main body to the first bend portion; and
a first straight portion extending at an angle from the first bend portion, the first straight portion including a first leadout end; and
a second leadout region including:
a second bend portion extending tangentially away from the main body;
a second helix portion that extends 180 degrees about the inner diameter of the electro-acoustic transducer from the main body to the second bend portion; and
a second straight portion extending at an angle from the second bend portion, the second straight portion including a second leadout end.
10. The voice coil assembly of claim 9 , wherein the first and second bend portions extend away from a bobbin and a diaphragm of the electro-acoustic transducer to the first and second straight portions, respectively.
11. The voice coil assembly of claim 9 , wherein the first helix portion extends tangentially from the main body to the first bend portion, and wherein the second helix portion extends tangentially from the main body of to the first bend portion.
12. The voice coil assembly of claim 9 , wherein the first and second helix portions are suspended in a space between a voice coil and an inner diameter of a sleeve of the electro-acoustic transducer.
13. An electro-acoustic transducer, comprising:
a main body;
a first leadout region including:
a first bend portion extending tangentially away from the main body;
a first helix portion that extends 180 degrees about an inner diameter of the electro-acoustic transducer from the main body to the first bend portion; and
a first straight portion extending at an angle from the first bend portion, the first straight portion including a first leadout end; and
a second leadout region including:
a second bend portion extending tangentially away from the main body;
a second helix portion that extends 180 degrees about the inner diameter of the electro-acoustic transducer from the main body to the second bend portion; and
a second straight portion extending at an angle from the second bend portion, the second straight portion including a second leadout end.
14. The electro-acoustic transducer of claim 13 , further comprising a bobbin and a diaphragm, wherein the first and second bend portions extend away from the bobbin and the diaphragm to the first and second straight portions, respectively.
15. The electro-acoustic transducer of claim 14 , further comprising a guide insert about the bobbin, the guide insert including first and second grooved elements, the first and second straight portions extending through the first and second grooved elements.
16. The electro-acoustic transducer of claim 15 , wherein the grooved element includes a rounded edge about which the bend portion of the of at least one of the first and second helical leadout regions is coupled.
17. The electro-acoustic transducer of claim 15 , further comprising a back plate coupled to the bobbin at a second end of a sleeve opposite a first end of the sleeve, the guide insert providing a positive stop for the back plate.
18. The electro-acoustic transducer of claim 13 , wherein the first helix portion extends tangentially from the main body to the first bend portion, and wherein the second helix portion extends tangentially from the main body of to the first bend portion.
19. The electro-acoustic transducer of claim 13 , wherein the first and second helix portions are suspended in a space between a voice coil and an inner diameter of a sleeve of the electro-acoustic transducer.