How to calculate Resonance Frequency of Audio Speaker?
You cannot CALCULATE Fs, (Resonant frequency of loudspeaker moving mass in free air).  But you can MEASURE it relatively easily.  You will need a power amp, a variable frequency source, and a DMM.  THere are many resources online for measuring driver characteristics. Fs is one of the primary measurements for the popular Thiele/Small parameters.  Here is one straightforward explanation:

Ref: https://sound-au.com/tsp.htm