There was some awful Boss tweeters in my malibu when i got it, hooked up to the door speakers with some sort of bass blockers, think they had one on each wire. Can't really remember I only had the door panel off briefly.
Long story short, they still sounded terrible at louder volumes, even with those things. Can't say I have ever had that problem with a true crossover in something like a component set. Cut the wires to them and the overall sound from the front is much better. Leaving them physically installed for now however because to remove them would leave 2 ugly holes in the tops of both of my pillar covers.