Loudspeaker protection

Patent metadata

Field	Value
Publication number	US-2018014121-A1
Application number	US-201615547850-A
Country	US
Kind code	A1
Filing date	Feb 1, 2016
Priority date	Feb 2, 2015
Publication date	Jan 11, 2018
Grant date	—

Abstract

This application describes methods and apparatus for loudspeaker protection. A loudspeaker protection system ( 100 ) is described having a first frequency band-splitter ( 102 ) for splitting an input audio signal (Vin) into a plurality of audio signals (v 1 , v 2 . . . , vn) in different respective frequency bands (ω 1, ω2 . . . , ωn). A first gain block ( 103 ) is configured to apply a respective frequency band gain (g 1 , g 2 . . . , g 3 ) to each of the audio signals in the different respective frequency bands and a gain controller ( 107, 108, 109 ) is provided for controlling the respective band gains. A displacement modeller ( 104, 105 ) determines a plurality of displacement signals (x 1 , x 2 . . . , xn) based on the input audio signal (Vin) and a displacement model ( 104 a ) where each displacement signal corresponds to a modelled cone displacement for the loudspeaker for one of said different respective frequency bands. The gain controller ( 107, 108, 109 ) is configured to control the respective frequency band gains based on the plurality of displacement signals.

First claim

1 . A loudspeaker protection system comprising:
a first frequency band-splitter configured to receive an input audio signal and split said input audio signal into a plurality of audio signals in different respective frequency bands; a first gain block configured to apply a respective frequency band gain to each of said plurality of audio signals in said different respective frequency bands; a gain controller for controlling said respective frequency band gains; and a displacement modeller configured to determine a plurality of displacement signals based on said input audio signal and a displacement model, each displacement signal corresponding to a modelled cone displacement for the loudspeaker for one of said different respective frequency bands; wherein said gain controller is configured to control said respective frequency band gains based on said plurality of displacement signals.

2 . A loudspeaker protection system as claimed in claim 1 wherein the displacement modeller comprises a displacement modelling block configured to receive an audio waveform signal and determine a predicted displacement for the loudspeaker based on said audio waveform signal and the displacement model.

3 . A loudspeaker protection system as claimed in claim 2 wherein said audio waveform signal is a version of said input audio signal.

4 . A loudspeaker protection system as claimed in claim 2 or claim 3 wherein the displacement modeller comprises a second frequency band-splitter configured to receive the output of said displacement modelling block and split said output into the plurality of displacement signals in different frequency bands, wherein said frequency bands of the second frequency band-splitter correspond to the frequency bands of the first frequency band-splitter.

5 . A loudspeaker protection system as claimed in claim 4 wherein said second frequency band-splitter comprises a filter-bank of band-pass filters.

6 . A loudspeaker protection system as claimed in claim 4 or claim 5 wherein the second frequency band-splitter comprises a rectifier to apply rectification in each frequency band to provide said plurality of displacement signals.

7 . A loudspeaker protection system as claimed in any of claims 4 to 6 wherein the second frequency band-splitter is configured to process the displacement signal in each frequency band so as to provide at least one of: an attack time constant; a decay time constant; or an indication of maximum displacement in a frame period.

8 . A loudspeaker protection system as claimed in claim 2 wherein said displacement modelling block is configured to receive said plurality of audio signals output from said first frequency band splitter and determine a modelled cone displacement for each of said audio signals output from said first frequency band splitter to provide the plurality of displacement signals in different frequency bands.

9 . A loudspeaker protection system as claimed in any preceding claim comprising a second gain block configured to apply a respective gain to each of said plurality of displacement signals in different frequency bands.

10 . A loudspeaker protection system as claimed in claim 10 wherein the respective gain applied to each of said plurality of displacement signals by said second gain block is based on the then present band gain corresponding to that frequency band as determined by the gain controller.

11 . A loudspeaker protection system as claimed in claim 9 or claim 10 further comprising a multi-band dynamic range control block wherein the respective gain applied to each of said plurality of displacement signals by said second gain block is based on a dynamic range control gain for the relevant frequency band determined by said multi-band dynamic range control block.

12 . A loudspeaker protection system as claimed in claim 11 wherein said multi-band dynamic range control block receives a version of said plurality of audio signals from the first frequency band-splitter to determine the dynamic range control gains.

13 . A loudspeaker protection system as claimed in claim 12 wherein, for at least some of the plurality of audio signals from the first frequency band splitter, the multi-band dynamic range control block is configured to combine the audio signal in one frequency band with at least one audio signal of an adjacent frequency band and process the combined audio signal to determine a dynamic range control gain for the respective frequency bands.

14 . A loudspeaker protection system as claimed in claim 12 or claim 13 comprising a delay block in a signal path for the plurality of the audio signals, wherein the delay block is downstream of the first frequency band-splitter and upstream of the first gain block and wherein the multi-band dynamic range control block receives a version of the plurality of audio signals that is derived from upstream of the delay block.

15 . A loudspeaker protection system as claimed in claim 11 wherein said multi-band dynamic range control block receives a version of said plurality of displacement signals and determines the dynamic range control gains from said displacement signals.

16 . A loudspeaker protection system as claimed in claim 15 wherein, for at least some of the plurality of displacement signals, the multi-band dynamic range control block is configured to combine the displacement signal in one frequency band with at least one displacement signal of an adjacent frequency band and process the combined displacement signal to determine a dynamic range control gain for the respective frequency bands.

17 . A loudspeaker protection system as claimed in any of claims 1 to 11 or 15 to 16 comprising a delay block in a main audio signal path between an input for the input audio signal and an output for an output audio signal, wherein the delay block is upstream of the first gain block.

18 . A loudspeaker protection system as claimed in claim 17 wherein the delay block is upstream of the first frequency band-splitter.

19 . A loudspeaker protection system as claimed in any of claims 9 to 18 comprising an over-excursion detector configured to determine whether an overall predicted cone excursion for said loudspeaker based on said plurality of displacement signals after the respective gain has been applied by said second gain block is or will exceed at least one threshold.

20 . A loudspeaker protection system as claimed in claim 19 wherein the over-excursion detector is configured to receive and combine said plurality of displacement signals after the respective gain has been applied by said second gain block to determine the overall predicted cone excursion for said loudspeaker.

21 . A loudspeaker protection system as claimed in any preceding claim wherein the gain controller is configured to control the band gain for each frequency band based on the displacement signal for that frequency band.

22 . A loudspeaker protection system as claimed in claim 21 wherein said gain controller is configured to control said band gains to maximise a sum of the band gains subject to remaining within an acceptable excursion limit.

23 . A loudspeaker protection system as claimed in claim 22 wherein said gain controller is configured to apply iterative error minimisation techniques to control said band gains.

24 . A loudspeaker protection system as claimed in any of claims 21 to 23 wherein said gain controller is configured to ide

Assignees

• Cirrus Logic Int Semiconductor Ltd

Inventors

• Lawrence Jason William
• Napoli Roberto
• Serwy Roger
• Su Jie
• Williams Stefan
• Hu Rong
• Azrai Firas

Classifications

• H04R3/04

  for correcting frequency response · CPC title

• H04R3/007 Primary

  Protection circuits for transducers · CPC title

• G10L21/0272

  Voice signal separating · CPC title

• H04R29/001

  for loudspeakers (H04R29/007 takes precedence) · CPC title

• H04R2430/01

  Aspects of volume control, not necessarily automatic, in sound systems · CPC title