If you want to buy a subwoofer for your automobile, you should know that there are three kinds of subwoofers you can choose from. Component Subwoofers- Comprises only the speaker. You require to buy other components separately. Active Subwoofers- These subwoofers come enclosed in the enclosure box with a built-in amplifier. These are easy to install and are compact to fit anywhere. Enclosed Subwoofers- These subwoofers come sitting in a box. However, if you want an amp, you will have to buy it separately.