It's possible that it's not related to the EQ at all,

It would all depend on what sort of crossover network you have installed. A crossover network limits the frequencies sent to a given speaker. Your tweeter should have had a crossover setting that would have prevented any frequencies lower than about 5,000 Hz getting to it*. Thus, any equalizer adjustments you were making in the lower frequencies would have had no effect on the tweeter.

If, however, you are not running any sort of crossover network (the crossovers could be active within the amplifier itself; or more likely passive crossovers wired in-line with the speakers, probably provided by the speaker manufacturer) then all bets are off. You can and most likely will let the smoke out of your tweeters the first time you crank the volume up to any (un)reasonable level.

tanstaafl.

* This is not strictly true -- the crossover will have something like a 12 decibel per octave dropoff. That means that if you had the crossover set nominally at 5,000 Hz, you would have 2500 Hz frequencies getting through it at 12 dB less volume; and 1250 Hz at 24dB less; and so on.

db