Midbass are most commonly mounted in the doors. Subwoofers Subwoofers add lower frequencies to the whole system. They have to be enclosed in a box, with the exception of free air subwoofers, which use the trunk as a box. There are many different types of boxes and implementations discussed in the subwoofers section. A few high-end manufacturers are making horns for car audio use.
Horns are very good at directing sound and have high efficiencies.
Horns are usually mounted under the dash. By doing this, difference in distance from left and right speakers are greatly reduced over conventional mounting locations. Since horns play mids and highs, tweeters are not needed. Even though horns are mounted under the dash, they give great imaging. Horns cost more than conventional speakers and require customization.