Transducer displacement protection
AssigneeBang & Olufsen Icepower A/S
InventorsMads Emil Solgaard, Bjørn Sand Jensen
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Abstract
This invention relates to the mechanical protection using digital processing and a predictive estimation of instantaneous displacement of the voice coil in a loudspeaker transducer. The invention solves the problem of limiting the coil displacement of the transducer by applying a look-a-head based linear or non-linear predictor and a controller operating directly on the displacement signal in order to finally convert back into the incoming signal domain.
Claims14
A method for controlling and limiting voice coil displacement of an electro dynamic transducer, the method comprising:
- predicting an instantaneous displacement signal based on a digital audio input signal;
- delaying the predicted displacement signal a predefined number of samples;
- controlling the delayed, predicted displacement signal using the predicted displacement signal as input, by:
- applying a gain function which multiplies a calculated gain factor, g(n), with the delayed predicted displacement signal, the calculated gain factor being calculated based on a ratio between the predicted instantaneous displacement signal and a displacement threshold xd,th determined by a total system gain and transducer characteristics, given as ratio(n)=xd,th/xd(n);
- applying an inverse filter structure to transform the predicted displacement signal into a signal domain of the digital audio input signal;
- amplifying the controlled signal domain signal;
- and
- applying the amplified controlled signal domain signal to the electro dynamic transducer.
A loudspeaker system, comprising:
- an amplifier to amplify a digital audio input signal;
- a transducer to receive an amplified signal from the amplifier;
- a predictor to predict an instantaneous displacement signal based on the digital audio input signal;
- a delay element to delay the predicted displacement signal a predefined number of samples;
- a controller to limit voice coil displacement of the transducer by controlling the delayed, predicted displacement signal using the predicted displacement signal as input;
- an inverse filter structure to transform the predicted displacement signal into a signal domain of the digital audio input signal;
- an amplifier to amplify the controlled signal domain signal and apply the amplified signal to the transducer,
- wherein the controller includes a gain element arranged to apply a gain function which multiplies a calculated gain factor, g(n), with the delayed predicted displacement signal, the gain factor being based on a ratio between the predicted instantaneous displacement signal and a displacement threshold xd,th, determined by a total system gain and transducer characteristics, given as ratio(n)=xd,th/xd(n).
A method for controlling and limiting voice coil displacement of an electro dynamic transducer, the method comprising:
- predicting an instantaneous displacement signal based on a digital audio input signal;
- delaying the predicted displacement signal by a fixed number of samples;
- controlling the delayed, predicted displacement signal using the predicted displacement signal as input, by:
- applying a gain function which multiplies a calculated gain factor, g(n), with the delayed predicted displacement signal, the calculated gain factor being calculated based on a ratio between the predicted instantaneous displacement signal and a displacement threshold xd,th determined by a total system gain and transducer characteristics, given as ratio(n)=xd,th/xd(n);
- applying an inverse filter structure to transform the predicted displacement into a signal domain of the digital audio input signal;
- amplifying the controlled signal domain signal;
- and
- applying the amplified signal to the electro dynamic transducer.
Dependencies are inferred from the claim text.