This is a superb technical note by JBL on the danger of under powering audio speakers.
Click on the Technical note below:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.cieri.net/Documenti/JBL/Technical%2520Notes/JBL%2520Technical%2520Note%2520-%2520Vol.1,%2520No.16.pdf&ved=2ahUKEwilqPKl1r7pAhUEUBUIHYbFA8IQFjAAegQIAhAC&usg=AOvVaw1S96lPIG7fLQddDmFoKroy