High displacement acoustic transducer systems
Acoustic transducer systems are described herein and in particular, acoustic transducer systems involving high displacement are described. An example acoustic transducer system includes an acoustic driver, a diaphragm position sensing module for generating a position signal corresponding to a displacement of a diaphragm of the acoustic driver, and a controller operable to: receive an input audio signal; generate a control signal based at least on the input audio signal and the position signal; and transmit the control signal to a voice coil operably coupled to the diaphragm so that the voice coil moves within an air gap within the acoustic driver at least partially in response to the control signal. A height of the voice coil can correspond substantially to a gap height in some embodiments.
1. An acoustic transducer system comprising:
a driver motor operable to generate a magnetic flux;
a diaphragm operably coupled to the driver motor;
a voice coil coupled to the diaphragm, the voice coil being movable at least in response to the magnetic flux;
a diaphragm position sensing module generating a position signal corresponding to a displacement of the diaphragm relative to an initial position of the diaphragm; and
a controller in electronic communication with the driver motor and the diaphragm position sensing module, the controller being operable to:
receive an input audio signal;
generate a correction signal based on the position signal, the correction signal compensating, at least, distortions associated with the detected displacement;
generate a motional feedback signal based on, at least, the position signal, the motional feedback signal operating to accommodate generation of a target response by the acoustic transducer system, the target response being a desired type of output signal for the acoustic transducer system;
generate a control signal based on, at least, the correction signal, a version of the input audio signal, and the motional feedback signal; and
transmit the control signal to the voice coil, the voice coil moving at least in response to the control signal.
2. The acoustic transducer system of claim 1 , wherein:
the driver motor comprises:
an axial post;
a bottom plate extending away from the axial post;
a top plate having an interior surface facing the axial post, wherein the top plate and the axial post defines an air gap therebetween; and
a magnetic element positioned between the bottom plate and the top plate, the magnetic element being spaced away from the axial post and the magnetic element operable to generate the magnetic flux; and
the voice coil is movable at least partially within the air gap.
3. The acoustic transducer system of claim 2 , wherein the voice coil has a coil height corresponding substantially to a gap height of the air gap.
4. The acoustic transducer system of claim 2 , wherein the axial post comprises a center post located at a substantially central region of the driver motor.
5. The acoustic transducer system of claim 2 , wherein the axial post comprises an outer wall of the driver motor.
6. The acoustic transducer system of claim 5 , wherein:
the magnetic element is coupled between the bottom plate and a bottom surface of the top plate; and
the driver motor further comprises a second magnetic element coupled to a top surface of the top plate, the top surface of the top plate being opposite from the bottom surface of the top plate.
7. The acoustic transducer system of claim 2 , wherein the top plate comprises an interior portion and an exterior portion coupled to the interior portion, a surface of the interior portion being the interior surface and the magnetic element being coupled to the top plate via the exterior portion, a height of the exterior portion being less than a height of the interior surface.
8. The acoustic transducer system of claim 7 , wherein at least one of a top surface and a bottom surface of the interior portion of the top plate is tapered towards the exterior portion.
9. The acoustic transducer system of claim 2 , wherein the magnetic element extends further away from the axial post than at least one of the bottom plate and the top plate.
10. The acoustic transducer system of claim 2 , wherein the axial post and the bottom plate define a driver cavity within the driver motor for at least partially receiving the voice coil.
11. The acoustic transducer system of claim 2 , wherein the driver motor is configured to accommodate a movement of the voice coil, the voice coil being movable towards and away from the bottom plate within a displacement range, the displacement range extends from each end of the air gap and the displacement range corresponds to at least a coil height of the voice coil.
12. The acoustic transducer system of claim 2 , wherein a cross-sectional area of the axial post is at most equal to an area of the interior surface.
13. The acoustic transducer system of claim 2 , wherein the axial post comprises a top portion and a bottom portion coupled to the top portion, a surface of the top portion partially facing the interior surface of the top plate and the bottom portion being coupled to the bottom plate.
14. The acoustic transducer system of claim 13 , wherein the bottom portion of the axial post is tapered away from the bottom plate.
15. The acoustic transducer system of claim 13 , wherein the top portion of the axial post is tapered away from the air gap.
16. The acoustic transducer system of claim 13 , wherein the top portion of the axial post partially extends away from the bottom plate for extending the gap height.
17. The acoustic transducer system of claim 1 , wherein the diaphragm position sensing module comprises a position sensor for detecting the displacement of the diaphragm.
18. An acoustic transducer system comprising:
a driver motor operable to generate a magnetic flux;
a diaphragm operably coupled to the driver motor;
a voice coil coupled to the diaphragm, the voice coil being movable at least in response to the magnetic flux;
a diaphragm position sensing module generating a position signal corresponding to a displacement of the diaphragm relative to an initial position of the diaphragm; and
a controller in electronic communication with the driver motor and the diaphragm position sensing module, the controller being operable to:
receive an input audio signal, wherein the controller is operable to receive the input audio signal from a current source;
generate a correction signal based on the position signal, the correction signal compensating, at least, distortions associated with the detected displacement;
determine a target response defined for the acoustic transducer system, the target response being a desired type of output signal for the acoustic transducer system;
generate a preprocessed input audio signal from the input audio signal with reference to the target response, the input audio signal being adjusted to accommodate generation of the desired type of output signal; and
generate a control signal based at least on the correction signal and the preprocessed input audio signal; and
transmit the control signal to the voice coil, the voice coil moving at least in response to the control signal.
19. The acoustic transducer system of claim 1 , wherein:
the controller comprises:
a velocity feedback module configured to generate a velocity correction signal based, at least, on the position signal; and
a low pass filter configured to generate a version of the position signal; and
the motional feedback signal comprises the velocity correction signal and the version of the position signal.
20. The acoustic transducer system of claim 1 , wherein:
at least one temperature sensor is coupled to the driver motor; and
the controller is further configured to:
estimate a temperature of the voice coil based on a temperature of the driver motor detected by the at least one temperature sensor; and
generate the correction signal to minimize changes in performance of the acoustic transducer system due to the estimated temperature.
21. The acoustic transducer system of claim 20 , wherein the at least one temperature sensor is coupled to the magnetic element.
22. The acoustic transducer system of claim 20 , wherein:
the acoustic transducer system comprises a suspension structure operably coupled to the voice coil; and
the at least one temperature sensor is coupled to the suspension structure.
23. The acoustic transducer system of claim 1 , wherein the controller is further operated to:
determine, from the position signal, whether the displacement of the diaphragm satisfies a displacement limit defined for the acoustic transducer system, the displacement limit representing a maximum displacement range for the acoustic transducer system; and
in response to determining the displacement of the diaphragm satisfies the displacement limit, not generate the control signal thereby causing no movement at the voice coil by the control signal, otherwise, generate the control signal based at least on the version of the input audio signal and the position signal.
24. The acoustic transducer system of claim 18 , wherein:
at least one temperature sensor is coupled to the driver motor; and
the controller is configured to:
estimate a temperature of the voice coil based on a temperature of the driver motor detected by the at least one temperature sensor; and
generate the correction signal to minimize changes in performance of the acoustic transducer system due to the estimated temperature.
25. The acoustic transducer system of claim 18 , wherein the controller is operated to:
determine, from the position signal, whether the displacement of the diaphragm satisfies a displacement limit defined for the acoustic transducer system, the displacement limit representing a maximum displacement range for the acoustic transducer system; and
in response to determining the displacement of the diaphragm satisfies the displacement limit, not generate the control signal thereby causing no movement at the voice coil by the control signal, otherwise, generate the control signal based at least on the version of the input audio signal and the position signal.