How do I access a tweeter on an elantra door?

You have to remove the door panel the tweeter is then available.

you may be able to access this also as other Hyundai service info at hmaservice.comhmaservice.com">hmaservice.com

remove door panel, then look if your stock speakers come with fitted tweeters. if they do, then just get a new set of speakers and get a set of tweeters for ten bucks off of aplusperfomance.com and bridge them to your new speakers. wire negative to negative and pos to pos with a wire. mount the tweeter wherever you want it.