90 db peaks is not overly loud in my opinion. The fact that you blew a tweater at this level is in my mind an indication that there is something wrong somewhere. This assumes that your amps are good amplifiers and not clipping when driving these Thiels to this level. These are a fairly power hungry speaker and I am suspicious of any "mass market" power amp's actual capabilities vs. rated. Not knowing your specific brand and model of amp, it would be hard to say. However, in reading your statement, you claim the amps are 200 WPC @ 4 ohms (which according to many manufacturers that means they are 100 wpc @ 8 ohms). If this is a high current amp, such as most of the Krells for example, then I would find this surprising. However, there are quite a few brands that I would not trust to drive this particular speaker at the rated output without clipping.
If you are pushing your amp too hard, this increases the potential to damage your speakers. If you review the threads on the Thiel speakers, I think you will find that most owners recommend feeding these speakers a lot of good class A power to drive them successfully. Personally, I would not even consider running these speakers without an absolute minimum of 200 WPC @ 8 ohms of high current, class A power and would prefer to have at least 300 watts @ 8 ohms.
Perhaps Thiel will be able to find something wrong with the tweeter itself which contributed to the failure.
If you are pushing your amp too hard, this increases the potential to damage your speakers. If you review the threads on the Thiel speakers, I think you will find that most owners recommend feeding these speakers a lot of good class A power to drive them successfully. Personally, I would not even consider running these speakers without an absolute minimum of 200 WPC @ 8 ohms of high current, class A power and would prefer to have at least 300 watts @ 8 ohms.
Perhaps Thiel will be able to find something wrong with the tweeter itself which contributed to the failure.