# US 2014/0153770 A1 · Acoustic transducer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153770 A1 - Document ID: US20140153770A1 - Status: Published application - Kind: A1 - Application number: 13/760,772 - Filed: 2013-02-06 - Published: 2014-06-05 - Earliest claimed: 2012-12-04 - Assignees: Sentient Magnetics, Inc. - Applicants: Sentient Magnetics, Inc. - Inventors: John B. French; David Russell - Web page: https://patentgrep.com/patent/US20140153770A1 ## CPC - H04R 3/00: Circuits for transducers (arrangements for producing a reverberation or echo sound G10K15/08; amplifiers H03F) - H04R 9/00: Transducers of moving-coil, moving-strip, or moving-wire type - H04R 9/06: Loudspeakers - H04R 9/025: {Magnetic circuit} - H04R 9/046: {Construction} - H04R 2209/021: Reduction of eddy currents in the magnetic circuit of electrodynamic loudspeaker transducer - H04R 2209/022: Aspects regarding the stray flux internal or external to the magnetic circuit, e.g. shielding, shape of magnetic circuit, flux compensation coils - H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K) ## Abstract This invention relates to acoustic transducers with stationary and moving coils, and methods for operating the acoustic transducers. Time varying signals are applied to the moving and stationary coils to control the movement of a diaphragm, which produces sound. The time varying signal applied to the moving coil corresponds to at least a processed version of an input audio signal and is updated based on, at least, a version of the time varying signal applied to the stationary coil. Some embodiments include updating the processed version of the input audio signal in response to a magnetic flux value corresponding to the time-varying signal applied to the stationary coil. Some embodiments include updating the time-varying signal applied to the moving coil in response to a feedback signal. ## Claims ### Claim 1 A method of operating an acoustic transducer, the method comprising: receiving an input audio signal; generating a time-varying stationary coil signal in a stationary coil, wherein the time-varying stationary coil signal corresponds to the input audio signal, wherein the stationary coil induces a magnetic flux in a magnetic flux path; generating a time-varying moving coil signal in a moving coil, wherein: the moving coil is disposed within the magnetic flux path; the time-varying moving coil signal corresponds to both the time-varying stationary coil signal and a processed version of the input audio signal; and the time-varying moving coil is coupled to a moving diaphragm which moves in response to the time-varying moving coil signal; and generating the processed version of the input audio signal in response to a magnetic flux value corresponding to the time-varying stationary coil signal. ### Claim 2 (depends on 1) The method of claim 1, wherein updating the processed version of the input audio signal further comprises: providing a target input audio signal in response to the input audio signal; and generating an updated processed version of the input audio signal, wherein the updated processed version of the input audio signal corresponds to the magnetic flux value and the target input audio signal. ### Claim 3 (depends on 2) The method of claim 2, wherein generating an updated processed version of the input audio signal further comprises: determining the updated processed version of the input audio signal based on a transfer function and the target input audio signal, wherein the transfer function corresponds to the magnetic flux value. ### Claim 4 (depends on 1) The method of claim 1 wherein the processed version of the input audio signal is iteratively updated in response to the magnetic flux value. ### Claim 5 (depends on 1) The method of claim 1, wherein the magnetic flux value is determined by a method selected from the group consisting of: looking up the magnetic flux value in a lookup table; and determining the magnetic flux value using a polynomial. ### Claim 6 (depends on 1) The method of claim 1, wherein generating a time-varying stationary coil signal further comprises: generating a stationary coil control signal corresponding to the input audio signal; and generating the time-varying stationary coil signal corresponding to the stationary coil control signal. ### Claim 7 (depends on 6) The method of claim 6, wherein generating a time-varying moving coil signal further comprises: dividing the processed version of the input audio signal by the stationary coil control signal. ### Claim 8 (depends on 1) The method of claim 1 wherein the acoustic transducer is a hybrid acoustic transducer including a permanent magnet that induces magnetic flux in the magnetic flux path, and wherein the time-varying stationary coil signal corresponds to both the magnetic flux induced by the permanent magnet and the input audio signal. ### Claim 9 An acoustic transducer comprising: an audio input terminal for receiving an input audio signal; a driver having: a moving diaphragm; a magnetic material having an air gap; a stationary coil for inducing magnetic flux in the magnetic material and the air gap; a moving coil coupled to the diaphragm wherein the moving coil is disposed at least partially within the air gap; and a control system adapted to: produce a time-varying stationary coil signal in the stationary coil, wherein the time-varying stationary coil signal corresponds to the input audio signal; produce a time-varying moving coil signal in the moving coil, wherein: the time-varying moving coil signal corresponds to both the time-varying stationary coil signal and a processed version of the input audio signal; and the time-varying moving coil is coupled to the moving diaphragm which moves in response to the time-varying moving coil signal; and generate the processed version of the input audio signal in response to a magnetic flux value corresponding to the time-varying stationary coil signal. ### Claim 10 (depends on 9) The acoustic transducer of claim 9, wherein the control system is further adapted to: provide a target input audio signal in response to the input audio signal; and generate an updated processed version of the input audio signal, wherein the updated processed version of the input audio signal corresponds to the magnetic flux value and the target input audio signal. ### Claim 11 (depends on 10) The acoustic transducer of claim 10, wherein the control system is further adapted to: iteratively update the processed version of the input audio signal based on a transfer function and the target input audio signal, wherein the transfer function corresponds to the magnetic flux value. ### Claim 12 (depends on 9) The acoustic transducer of claim 9, wherein the magnetic flux value is determined by a method selected from the group consisting of: looking up the magnetic flux value in a lookup table; and determining the magnetic flux value using a polynomial. ### Claim 13 (depends on 9) The acoustic transducer of claim 9, wherein the control system is further adapted to: generate a stationary coil control signal corresponding to the input audio signal; and generate the time-varying stationary coil signal corresponding to the stationary coil control signal. ### Claim 14 (depends on 13) The acoustic transducer of claim 13, wherein the control system is further adapted to: divide the processed version of the input audio signal by the stationary coil control signal. ### Claim 15 (depends on 9) The acoustic transducer of claim 9 further comprising a permanent magnet for inducing magnetic flux in the air gap, wherein the control system is adapted to produce the time-varying stationary coil signal corresponding to both the input audio signal and the magnetic flux induced by the permanent magnet in the air gap. ### Claim 16 A method of operating an acoustic transducer, the method comprising: receiving an input audio signal; generating a time-varying moving coil signal in a moving coil, wherein: the moving coil is disposed within a magnetic flux path; the time-varying moving coil signal corresponds to at least a processed version of the input audio signal; and the moving coil is coupled to a moving diaphragm which moves in response to the time-varying moving coil signal; generating a feedback signal for updating the time-varying moving coil signal; applying a time-varying stationary coil signal in a stationary coil, wherein the stationary coil induces a magnetic flux in the magnetic flux path, and wherein the time-varying stationary coil signal corresponds to the feedback signal; and updating the time-varying moving coil signal in response to the feedback signal. ### Claim 17 (depends on 16) The method of claim 16, wherein generating a feedback signal for updating the time-varying moving coil signal further comprises: determining a stationary coil loss and a moving coil loss, the stationary coil loss corresponds to a loss at the stationary coil and the moving coil loss corresponds to a loss at the moving coil; determining a power balancing signal, wherein the power balancing signal corresponds to a difference between the stationary coil loss and the moving coil loss; and determining the feedback signal based on the power balancing signal. ### Claim 18 (depends on 16) The method of claim 16, wherein generating a time-varying moving coil signal further comprises: dividing the processed version of the input audio signal by the feedback signal. ### Claim 19 (depends on 16) The method of claim 16, wherein updating the time-varying moving coil signal further comprises: providing a target input audio signal corresponding to the input audio signal; and generating an updated processed version of the input audio signal based on the target input audio signal. ### Claim 20 (depends on 19) The method of claim 19, wherein generating an updated processed version of the input audio signal further comprises: determining a feedback magnetic flux value corresponding to the feedback signal; and iteratively updating the processed version of the input audio signal based on a transfer function and the target input audio signal, wherein the transfer function corresponds to the feedback magnetic flux value. ### Claim 21 (depends on 20) The method of claim 20, wherein the feedback magnetic flux value is determined by a method selected from the group consisting of: looking up the magnetic flux value in a lookup table; and determining the magnetic flux value using a polynomial. ### Claim 22 (depends on 16) The method of claim 16 the acoustic transducer is a hybrid acoustic transducer including a permanent magnet that induces magnetic flux in the magnetic flux path, and wherein the time-varying stationary coil signal corresponds to both the magnetic flux induced by the permanent magnet and the input audio signal. ### Claim 23 An acoustic transducer comprising: an audio input terminal for receiving an input audio signal; a driver having: a moving diaphragm; a magnetic material having an air gap; a stationary coil for inducing magnetic flux in the magnetic material and the air gap; a moving coil coupled to the diaphragm wherein the moving coil is disposed at least partially within the air gap; and a control system adapted to: generate a time-varying moving coil signal in the moving coil, wherein: the time-varying moving coil signal corresponds to at least a processed version of the input audio signal; and the moving coil is coupled to the moving diaphragm which moves in response to the time-varying moving coil signal; generate a feedback signal for updating the time-varying moving coil signal; apply a time-varying stationary coil signal in the stationary coil, wherein the time-varying stationary coil signal corresponds to the feedback signal; and update the time-varying moving coil signal in response to the feedback signal. ### Claim 24 (depends on 23) The acoustic transducer of claim 23, wherein the control system is further adapted to: determine a stationary coil loss and a moving coil loss, wherein the stationary coil loss corresponds to a loss at the stationary coil and the moving coil loss corresponds to a loss at the moving coil; determine a power balancing signal, wherein the power balancing signal corresponds to a difference between the stationary coil loss and the moving coil loss; and determine the feedback signal based on the power balancing signal. ### Claim 25 (depends on 23) The acoustic transducer of claim 23, wherein the control system is further adapted to: divide the processed version of the input audio signal by the feedback signal. ### Claim 26 (depends on 23) The acoustic transducer of claim 23, wherein the control system is further adapted to: provide a target input audio signal corresponding to the input audio signal; and generate an updated processed version of the input audio signal based on the target input audio signal. ### Claim 27 (depends on 26) The acoustic transducer of claim 26, wherein the control system is further adapted to: determine a feedback magnetic flux value corresponding to the feedback signal; and iteratively update the updated processed version of the input audio signal based on a transfer function and the target input audio signal, wherein the transfer function corresponds to the feedback magnetic flux value. ### Claim 28 (depends on 27) The acoustic transducer of claim 27, wherein the feedback magnetic flux value is determined by a method selected from the group consisting of: looking up the magnetic flux value in a lookup table; and determining the magnetic flux value using a polynomial. ### Claim 29 (depends on 23) The acoustic transducer of claim 23 further comprising a permanent magnet for inducing magnetic flux in the air gap, wherein the control system is adapted to produce the time-varying stationary coil signal corresponding to both the input audio signal and the magnetic flux induced by the permanent magnet in the air gap.