An acoustic apparatus includes a class-D amplifier including a current feedback circuit, and a speaker system including a voice coil driven by the class-D amplifier. The speaker system is configured such that, in a case where the speaker system is driven by an ordinary amplifier having a first output resistance lower than a second output impedance of the class-D amplifier, a Q factor of the speaker system falls below a predetermined lower limit of an ordinary Q factor range of an ordinary speaker system. The current feedback circuit is configured to increase the second output impedance of the class-D amplifier by feeding a current flowing to the voice coil back to an input of the class-D amplifier so as to increase a Q factor as the acoustic apparatus higher than the predetermined lower limit of the ordinary Q factor range and within the ordinary Q factor range.

Method and electronic circuit for determining a scaling factor k for a driving force function of a model of an electrodynamic acoustic transducer having at least two voice coils. Input signal fed into the transducer and it's model cause electromotive forces. A shift for the driving force function is determined on the base of the ratios between the real electromotive forces and the modeled electromotive forces. Finally, the scaling factor k is determined on the basis of a deviation between the real electromotive forces and the modeled electromotive forces at time points where the real electromotive forces and the modeled electromotive forces each are equal. The invention moreover relates to an electronic circuit for performing the above steps, and to a transducer system with the electronic circuit and a connected transducer.

Method and electronic circuit for determining a scaling factor k for a driving force function of a model of an electrodynamic acoustic transducer having at least two voice coils. Input signal fed into the transducer and it's model cause electromotive forces. A shift for the driving force function is determined on the base of the ratios between the real electromotive forces and the modeled electromotive forces. Finally, the scaling factor k is determined on the basis of a deviation between the real electromotive forces and the modeled electromotive forces at time points where the real electromotive forces and the modeled electromotive forces each are equal. The invention moreover relates to an electronic circuit for performing the above steps, and to a transducer system with the electronic circuit and a connected transducer.

An apparatus for processing an audio input signal having one or more audio input channels to obtain an audio output signal having one or more audio output channels has an estimation unit configured to estimate a radiation resistance of each driver of one or more drivers of each loudspeaker of one or more loudspeakers as an estimated radiation resistance; or as an estimated radiation impedance, wherein said estimated radiation impedance has estimated information on the radiation resistance of said driver; and a processing unit configured to obtain the audio output channels by processing each audio input channel depending on the estimated radiation resistance or the estimated radiation impedance of each driver of each loudspeaker. The estimation unit is configured to estimate the estimated radiation resistance or the estimated radiation impedance depending on estimated sound pressure information indicating an estimation of sound pressure at said driver of said loudspeaker, and depending on estimated velocity information indicating an estimation of a driver velocity of said driver of said loudspeaker.

An apparatus for processing an audio input signal having one or more audio input channels to obtain an audio output signal having one or more audio output channels has an estimation unit configured to estimate a radiation resistance of each driver of one or more drivers of each loudspeaker of one or more loudspeakers as an estimated radiation resistance; or as an estimated radiation impedance, wherein said estimated radiation impedance has estimated information on the radiation resistance of said driver; and a processing unit configured to obtain the audio output channels by processing each audio input channel depending on the estimated radiation resistance or the estimated radiation impedance of each driver of each loudspeaker. The estimation unit is configured to estimate the estimated radiation resistance or the estimated radiation impedance depending on estimated sound pressure information indicating an estimation of sound pressure at said driver of said loudspeaker, and depending on estimated velocity information indicating an estimation of a driver velocity of said driver of said loudspeaker.

A speaker drive unit includes a control signal generation unit and a signal processing unit. The control signal generation unit generates a control signal on the basis of detection signals generated by a plurality of detection units that is disposed in one-to-one correspondence with a plurality of actuators that vibrates a diaphragm, and detects vibration conditions. The signal processing unit includes a plurality of signal systems corresponding one-to-one to the plurality of actuators. The signal systems provide a drive signal to the corresponding actuators on the basis of the same audio signal. The drive signal generated by at least one signal system of the signal systems is controlled by the control signal.

A bone anchored hearing device includes an electromagnetic vibrator for generating a vibration in order to transmit sound through a bone of a user to an ear of the user; and a compensator for at least in part compensating a distortion in the vibration of the electromagnetic vibrator. Further, a signal processing method for a bone anchored hearing device includes providing, by an input transducer, an electric input signal representing sound of a surrounding of a user of the bone anchored hearing device; processing, by a signal processing unit, the electric input signal and providing a processed electric signal; generating, by an electromagnetic vibrator, based on the processed electric signal, a vibration in order to transmit sound through a bone of the user to an ear of the user; and at least in part compensating, by a compensator, a distortion in the vibration of the electromagnetic vibrator.

The invention provides a loudspeaker nonlinear compensation method. The method includes steps: obtaining system parameter of the loudspeaker, the No. i time-domain excitation voltage signal and the No. i state vector of the loudspeaker; compensating the No. i time-domain excitation voltage signal according to the system parameter and the No. i state vector and obtain i compensation voltage signal; obtaining the No. i+1 state vector according to the calculation of the system parameter and the No. i compensation voltage signal; outputting the No. i compensation voltage signal and record the quantity of the compensation voltage signal; judging whether the quantity of the compensation voltage signal is equal to the preset number value.

The invention provides a loudspeaker nonlinear compensation method. The method includes steps: obtaining system parameter of the loudspeaker, the No. i time-domain excitation voltage signal and the No. i state vector of the loudspeaker; compensating the No. i time-domain excitation voltage signal according to the system parameter and the No. i state vector and obtain i compensation voltage signal; obtaining the No. i+1 state vector according to the calculation of the system parameter and the No. i compensation voltage signal; outputting the No. i compensation voltage signal and record the quantity of the compensation voltage signal; judging whether the quantity of the compensation voltage signal is equal to the preset number value.

Electrical circuitry adapted to drive a dual-coil loudspeaker having a primary voice coil and a second voice coil connected in parallel with the primary voice coil, the second voice coil being in series with an LC resonant circuit of impedance Z.sub.mf, further comprising an inductance compensation filter of impedance Z.sub.if in parallel with the LC resonant circuit.