Patent ID: 7961892
Filing Date: 2011-06-14
Classification: H04R

Abstract:
1. An apparatus for measuring speaker cone displacement relative to a fixed position in an audio speaker having a voice coil aligned with the speaker cone along a central axis, the apparatus comprising: (a) a variable reluctance sensor device; said sensor device including a first unit fixed relative to said fixed position; and a second unit affixed to said speaker cone effecting relative motion between said first unit and said second unit through motion of said speaker cone at a position on said cone, said first unit and said second unit disposed coaxially about a second axis radially offset from said central axis; (b) a signal injecting circuit coupled for injecting a predetermined input signal into one of said first and second units; and (c) a signal receiving circuit coupled with said one of said first and second units for receiving a signal resulting from modulation of said input signal due to variation of reluctance of said sensor device caused by displacement of said first unit relative to said second unit, and for generating an indicating signal based upon said resulting signal; at least one signal characteristic of said indicating signal being related with said cone displacement.