Exactly what he said... I run coax + tweeter on both sets of mine... Its fine to add them right there just make sure your tweeter has a built in crossover(little tube thing on speaker wire) Or external crossover... Changes your ohm impedience, im pretty sure, 4ohm coax + 4ohm tweeter = 2ohm load... I'll check when I take deck out this week... But i'm running 4 coax + 4tweeters on deck and its fine... Sounds great much better than just coax...