Fabricating an integrated loudspeaker piston and suspension
A diaphragm and suspension for an electroacoustic transducer are formed by depositing a layer of compliant material on a first surface of a solid substrate and removing material from a second surface of the solid substrate. The removal leaves a block of substrate material suspended within an inner perimeter of an outer support ring of the substrate material by the compliant material, the block providing the diaphragm.
1. A diaphragm and suspension assembly for an electroacoustic transducer, the assembly comprising:
a piston comprising a disk of silicon having a flat surface, the flat surface serving as the diaphragm;
a support ring of silicon surrounding the piston and separated from the piston by a gap;
a layer of compliant material adhered to a top surface of the support ring and to the flat surface of the piston, suspending the piston in the gap, the compliant material having a mechanical stiffness in the range of 5-100 N/m.
2. The piston and suspension assembly of claim 1 , wherein the piston further comprises a void within the disk of silicon, bounded by a perimeter wall of the disk and the top surface of the disk.
3. The piston and suspension assembly of claim 1 , wherein the support ring comprises an inner perimeter wall of silicon facing the gap, and an outer lip having less height than the inner perimeter wall.
4. The piston and suspension assembly of claim 1 , wherein the compliant material has an elastic strain limit of at least 50 percent.
5. The piston and suspension assembly of claim 1 , wherein the compliant material has an elastic strain limit of at least 150 percent.
6. The piston and suspension assembly of claim 1 , wherein the support ring has an outer diameter of around 3 mm.
7. The piston and suspension assembly of claim 1 , wherein the compliant material comprises liquid silicone rubber (LSR).
8. The piston and suspension assembly of claim 1 , wherein the support ring has an outer diameter of around 4 mm.
9. The piston and suspension assembly of claim 1 , wherein the piston has a thickness of between 10 and 100 μm.
10. The piston and suspension assembly of claim 9 , wherein the piston has a thickness of about 50 μm.
11. The piston and suspension assembly of claim 1 , wherein the layer of compliant material is between 10 and 500 μm thick.
12. The piston and suspension assembly of claim 1 , wherein the layer of compliant material is around 50 μm thick.
13. An electro-acoustic transducer comprising:
a piston comprising a disk of silicon having a flat surface, the flat surface serving as a diaphragm of the transducer;
a support ring of silicon surrounding the piston and separated from the piston by a gap;
a layer of compliant material adhered to a top surface of the support ring and to the flat surface of the piston, suspending the piston in the gap, the compliant material having a mechanical stiffness in the range of 5-100 N/m;
a bobbin coupled to the piston;
a ferromagnetic housing coupled to the support ring; and
a magnet/voice-coil system coupled to the housing and bobbin for converting electrical current to motion of the piston.
14. The transducer of claim 13 , wherein:
the piston further comprises perimeter wall of the disk and the top surface of the disk, the perimeter wall and top surface bounding a void within the disk of silicon; and
the bobbin is adjacent to an inner perimeter of the perimeter wall of the disk.
15. The transducer of claim 13 , wherein:
the support ring comprises an inner perimeter wall of silicon facing the gap, and an outer lip having less height than the inner perimeter wall; and
the ferromagnetic housing is adjacent to an outer perimeter surface of the inner perimeter wall and a bottom surface of the outer lip.