How Can I Measure the Movement of a Loudspeaker Membrane?

[morten84]

Hi, I'm kinda new her, so I hope this is the right place to post this.
English is not my native language, so you might experience some spelling error:)

I am working on a project that my teacher assigned med the other day, were I am supposed to find out how i can measure the movement/velocity of a loudspeaker membran.

To find the movement/velocity of the membran i believe i must fint the movement of the voice coil.

(Not 100% this is the way to go)

Can this be done by measuring the differrent between the current and voltage feeding the loudspeaker?

Anyone have any ideas?

 

[light_bulb]

i believe you can get most of the info from Qts, Vas, spl/w and Qmax specs. or with optical feedback with a encoder type setup.

 

[Panda]

If you are finding the movement of a specific speaker with no specification as a project then you need to design an experiment to physically measure the deflection when a known amplitude sine wave is applied.
If you just have the specifications then you need to relate the electrical power the speaker draws in Watts to the noise power emitted in dB. You should be able to calculate the air movement required for a particular db level in standard atmosphere and then equate that to movement of the speaker cone for an input power.