So one of the satellite speakers fell and the wiring (either external or internal) has been disconnected or damaged - correct?
External wiring:
https
/www.google.com/search?q=edifier+mp+300+circuit+diagram&tbm=isch&source=lnms&sa=X&ved=0ahUKEwik6ZD1i9LVAhVIOSYKHTWIAVAQ_AUIeSgB&biw=1920&bih=963#imgrc=JdlfkcI1UH7pAM:
Internal wiring:
Now if, when the speaker fell, it broke the internal wiring/components, you will need a circuit diagram to reconstruct/repair the wiring.
Google: edifier mp300 circuit wiring diagrams to see if you can find some match.
Or use the other satellite speaker's internal wiring as a guide