Speaker enclosures

My direct drive Malibu has speakers cut into the dash and in the rear along the side pockets. Typical direct drive installation for years. I also have a sub under the dash at the drivers fee. The speakers really have no enclosure and are fairly open to air. My system sounds good and for the most part the only time it is really turned up is while running the boat. Otherwise I prefer to keep the volume down where you can speak over the system. Regardless, is there something I should do to increase the performance in these locations.