tweeter too loud

Went to components for front speakers. Placed the tweeters up high on the door panel. They are too loud. This component setup uses a basic highpass (capacitor) and does not have a crossover with level control. How can I make the tweeter output less (or variable) so that I can better balance it with the rest of the speakers in the truck. Using the radio control causes the other speakers to get dull sounding. Know ohms law and basic understanding of impedance. Need approach that reduces volume without introducing side effects such as turning circuit into a lowpass.John