Hello folks. I was very interested in this conversation, as several people were making claims as if they were facts. An overwhelming number of posters agreed that changing the tweeter was a mistake, and then did not actually answer the question. This is ridiculous. and then j_audio claimed this was common sense and then I just got upset at this fucking ridiculousness.
So first of all, I investigated the wiring and it turns out that in my JSW, there is a green wire that is the postive lead. And no, there would never ever be two positive leads to be connected. Seriously... Who visits this board? The other two leads (brown and purple) are negative and ground, and those two are to be connected together.
And finally, I whole heartedly disagreed with the saying that changing the tweeter will destroy sound. I have been doing home and car audio for a couple of decades now, and the first mistake is to assume a crossover can be "special." I've built crossovers, and have entertained the notion that it's important to use expensive capacitors and blah blah blah. Whatever. The designers of the sound system in these automobiles, probably looked at some generic three way crossover diagrams, selected a few resistors, capacitor and inductors and called it a day. Makers of high end audio charge a lot because they put more care into creating drivers that are tonally balanced. In home audio, this is especially important because they can place the speaker and enclosure in an anechoic chamber and make small adjustments. This is irrelevant in car audio, because you can't even control the enclosure and less likely the road noise etc.
It was obvious that the midbass and midrange for my JSW were perfect (probably by accident!) but seriously, the crossover is fine. It has certain crossover points similar to almost any three way speaker. And my dynaudio three ways in my 350z were pure bliss on the show room floor (as expected) but were a nightmare in the car. Even after 100 pounds of dynamat (and you think I'm kidding) those dynaudios could NEVER sound as good as when the car was standing still.
Anyway, I'm rambling. My point. I took the challenge and replaced only the tweeters with Hertz HT 20's. The results are amazing. Interestingly, I like this system with stock amp just as good as my dynaudio system (at freeway speed and normal listening volume).
You may not share my enthusiam, but I can say with 100% certainty that changing tweeters did NOT ruin my system.