Oh, Yamin, if you are able to cut the cone out of your damaged one ond post photos of the voice coil here, I think it would be very interesting to see the failure mode.
I can't do that yet with mine, they belong to the customer and I am not going to replace them.
I suspect a design issue rather than just being blown up by excessive power, maybe a hot spot shorts the turns.
Neither of my voice coils are rubbing on the magnet, which usually happens when speakers get melted.
hi, i rewind in young age some tweeters with that type of fault, one end of the wire was not properly secured (the external one, when the coil was finished by the machine, let's call it the 'end') and in time the insulation between the coil end and the coil 'start' was deteriorating and caused low impedance.
cause i'm lazy, i just eliminated that final loop or maybe 2 loops, the tweeter was ok for another 5 years. what do you want, students have no time
the problem may be like i described maybe, maybe not.
finding another amp to test the speaker should be not so complicated if frequency generator or another testing gear is not available, of finding another good speaker to test the amp...