I've installed JBL 6inch Splits into the front doors. I've also applied sound deadening around the speaker location for better woofer response and less rattles in the door.

I've also mounted the tweeter inside the door right next to the woofer and cross-over. Everything fits perfectly. The reason why I did this is because I didn't want to modify the OEM doors and flush mount the tweeter into it.

Sound is still good but not as direct as it can be. But then again I don't like too much treble that a lot of tweeters put out. I like it smooth so dampening the effect of the tweeter suits my opinion of good sound.