Blown tweeters

I, and my son at every party he had, blew the tweeters of my JSE Infinite Slope Model II's. His friends would have the wrong input, turn the volume up, up, nothing, then OH, change the input: crack, sizzle, pop

JSE used the highly respected Dynaudio D21 Tweeters. They just couldn't take a shot.

I got advice from Madisound, picked alternate tweeters with more ferrofluid in their design. Never blew

https://www.madisoundspeakerstore.com/welcome?gad_source=1&gclid=CjwKCAiAsIGrBhAAEiwAEzMlC03TIeThiwYI5b2OJlQpoPcsJa2bdHmvTmLdxoRiGg3upkkpEJXnhBoC2pMQAvD_BwE

Parts express always gives me good advice.

https://www.parts-express.com/?utm_source=google&utm_medium=cpc&utm_campaign=6443420617&utm_content=78474321778&utm_term=parts%20express&gadid=681697395974&gad_source=1&gclid=CjwKCAiAsIGrBhAAEiwAEzMlC6794vku-bYgqi2RTZ9Y5rWjVuRe6C9IKngtlJ50j21Y7EGOurHtdBoC1GIQAvD_BwE

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IF your tweeters are unique, then you need to have them repaired, AND, as you asked, 'why did they blow', as you don't want to fix and blow them again.

Concerned: you could try inexpensive tweeters for a while, if no problem surfaces, then install repaired ones. They better sound better!

Contact the manufacturer.  The crossovers may have protection circuits. 

I did he was stumped as to why both speakers would blow tweeter at same time

How do you know they are blown, by the way? 

Often we don't even hear when a tweeter goes out.  A midrange though... :)

In any event, lots of things can go wrong before the tweeter.  If you wanted to thoroughly diagnose it, get a Dayton audio DATS V2 to measure the impedance of your whole speaker a swell as the drivers out of the box. 

One step below that is to remove the tweets and test with an Ohm meter.  See if you have a short (no Ohms) or open (overloaded or infinite Ohms) circuit.