Few questions about speakers here: 1) Is there any gray area to blowing/damaging a speaker? Meaning...can a speaker be sort of worn out or damaged, or is it either the speaker is working perfectly or the speaker is completely blown. Basically, does a speaker in an amp wear out over time? 2) What's the main cause to blowing/damaging a speaker? 3) Can tweeters be damaged, if so, how? 4) What's the best way to tell if any of the above questions have happened?