Dynamic microphone unit and dynamic microphone
A dynamic microphone includes: a diaphragm; a voice coil fixed to the diaphragm; a magnetic circuit which includes a magnetic gap in which the voice coil is arranged and generates a magnetic field in the magnetic gap; a volume reducing member which is attached to the magnetic circuit, is arranged in a back surface space of the diaphragm, and reduces a volume in an air chamber in the back surface space; a communication passage which is formed along between the volume reducing member and the magnetic circuit and communicates the back surface space with a back side air chamber; and an acoustic resistance which is attached to the magnetic circuit and intervenes between the communication passage and the back side air chamber.
1. A dynamic microphone unit, comprising:
a diaphragm;
a voice coil fixed to the diaphragm;
a magnetic circuit which includes a magnetic gap in which the voice coil is arranged and generates a magnetic field in the magnetic gap;
a volume reducing member which is attached to the magnetic circuit, is arranged in a back surface space of the diaphragm, and reduces a volume in an air chamber in the back surface space;
a communication passage which is formed along between the volume reducing member and the magnetic circuit and communicates the back surface space with a back side air chamber formed on a back side of the magnetic circuit; and
an acoustic resistance which is attached to the magnetic circuit and intervenes between the communication passage and the back side air chamber,
wherein a surface of the volume reducing member facing the magnetic circuit includes a bonding surface bonding to the magnetic circuit and a cut-out portion forming the communicating passage along between the volume reducing member and the magnetic circuit.
2. A dynamic microphone unit, comprising:
a diaphragm;
a voice coil fixed to the diaphragm;
a magnetic circuit which includes a magnetic gap in which the voice coil is arranged and generates a magnetic field in the magnetic gap;
a volume reducing member which is attached to the magnetic circuit, is arranged in a back surface space of the diaphragm, and reduces a volume in an air chamber in the back surface space; and
an acoustic resistance comprising a thin air layer, which is formed along between the volume reducing member and the magnetic circuit and communicates the back surface space with a back side air chamber formed on a back side of the magnetic circuit,
wherein a surface of the volume reducing member facing the magnetic circuit includes a bonding surface bonding to the magnetic circuit and a cut-out portion forming the acoustic resistance comprising the thin air layer along between the volume reducing member and the magnetic circuit.
3. The dynamic microphone unit according to claim 1 , wherein a through-hole formed in the magnetic circuit is intervened between the communication passage and the back side air chamber, and the acoustic resistance formed in a column shape is arranged in the through-hole.
4. The dynamic microphone unit according to claim 3 , wherein the volume reducing member is supported on the magnetic circuit by the acoustic resistance formed in the column shape.
5. The dynamic Microphone unit according to claim 1 , wherein a through-hole formed in the magnetic circuit is intervened between the communication passage and the back side air chamber, and the acoustic resistance formed in a sheet-like shape is arranged between the through-hole and the back side air chamber to close the through-hole.
6. The dynamic microphone unit according to claim 1 , wherein the diaphragm comprises a center dome, in which a front surface is projected in a hemisphere shape, and an annular sub dome formed along a peripheral edge of the center dome, and a surface opposing to the center dome in the volume reducing member is formed in a spherical shape along a back surface of the center dome.
7. The dynamic microphone unit according to claim 2 , wherein the diaphragm comprises a center dome, in which a front surface is projected in a hemisphere shape, and an annular sub dome formed along a peripheral edge of the center dome, and a surface opposing to the center dome in the volume reducing member is formed in a spherical shape along a back surface of the center dome.
8. The dynamic microphone unit according to claim 6 , wherein the sub dome is annularly formed along the peripheral edge of the center dome, and a front surface of the sub dome is formed so as to project in an arc shape, and a second volume reducing member which is annularly formed along a back surface of the sub dome and in which a front surface is projected in an arc shape is further arranged in a back surface space of the sub dome.
9. The dynamic microphone unit according to claim 7 , wherein the sub dome is annularly formed along the peripheral edge of the center dome, and a front surface of the sub dome is formed so as to project in an arc shape, and a second volume reducing member which is annularly formed along a back surface of the sub dome and in which a front surface is projected in an arc shape is further arranged in a back surface space of the sub dome.
10. A dynamic microphone, wherein the dynamic microphone unit according to claim 1 is assembled in a microphone case.
11. A dynamic microphone, wherein the dynamic microphone unit according to claim 2 is assembled in a microphone case.
12. The dynamic microphone unit according to claim 1 , wherein the cut-out portion extends from a center of the volume reducing member facing the magnetic circuit to an edge of the volume reducing member in a radial direction of the volume reducing member.
13. The dynamic microphone unit according to claim 12 , wherein the bonding surface includes a plurality of bonding sections, the cut-out portion includes a plurality of cut-out sections, and each cut-out section is formed between two bonding sections adjacent to each other.
14. The dynamic microphone unit according to claim 13 , wherein the volume reducing member further comprises a bottomed hole having an opening arranged at the center of the volume reducing member facing the magnetic circuit.
15. The dynamic microphone unit according to claim 2 , wherein the cut-out portion extends from a center of the volume reducing member facing the magnetic circuit to an edge of the volume reducing member in a radial direction of the volume reducing member.
16. The dynamic microphone unit according to claim 15 , wherein the bonding surface includes a plurality of bonding sections, the cut-out portion includes a plurality of cut-out sections, and each cut-out section is formed between two bonding sections adjacent to each other.
17. The dynamic microphone unit according to claim 16 , wherein the volume reducing member further comprises a bottomed hole having an opening arranged at the center of the volume reducing member facing the magnetic circuit.