Fused tweeters,is is common ?

the answer to your question about fusing tweeters and even other speakers as well is more common than people think.. It is especially good to fuse them if you get a little caried away with the volume control. 100 hz sounds about right for mids but where do you have you subs crossed over at . If you just have mids and tweeters for your highs and you have a sub for your lows.  A 100 hertz and below is common for subs and in this surcumstance 100 hz and above for your mids, and if you have components the crosover network that came whith the quarts will take care of the crossover point for the tweeters. I have even seen mids at 80 hertz and above listen for your self at different frequencies to see where it sounds best to you then cross your sub with that and see if you like. Play with diferent setting untill you get the sound you are looking for. good luck.

is your 5.25 a component set that came with its own tweeter and crosover ?

Yes,but i will be using an active crossover instead of the passive that the Quarts came with.The sub is A/D/S/ 310RS (10")in a sealed enclosure i think i will cross it over at  80 or 120 Hz no more.Dan M C

See some crossovers that come with components limit the power to the tweeters when the volume gets turned up  ie (the little light you see glowing),i dont know if yours has that but if you plan on not using the crossovers it may be a good idea to fuse them tweeters as excess power and or distortion  can easilly blow them.If you tell me the maximum (rms) power handling of them tweeters i can tell you the size of the fuse you will need to put there. I mean a fuse is a lot cheaper than new tweeters.