For the maximum possible performance and individuality in the box measurements, you should use a single subwoofer. A single subwoofer is just the driver itself - it must be built into a calculated subwoofer box to work properly. You will also need to power the subwoofer via an external amplifier. Individual subwoofers usually range in size from 8" to 15". There are models that can operate at low or high power, and function in a variety of different box types and sizes. There is the widest selection of drivers, perfectly matched to your individual needs, as well as different impedance and voice coil configurations, so you can choose the models that best suit your system. If you're starting from scratch when planning your individual system, choosing a subwoofer is a good place to start. We will be happy to advise you on what suits your needs. By the way: We can also build and calculate a subwoofer enclosure according to your dimensions and requirements. If you want more bass in your car quickly, easily and simply, take a look at our subwoofer enclosures. Subwoofer enclosures are supplied ready-built in a box that has been specially developed for the subwoofer. This means you don't have to build an enclosure for the subwoofer and don't have to put as much work into planning and building your system. All you need is an external amplifier to power the subwoofer. We will be happy to advise you on which amplifier is the right one. The special form of cabinet subwoofers: The active subwoofer box. An active subwoofer combines an amplifier and a woofer in one enclosure. As the amplifier is already integrated in the cabinet, you don't need much space. Many active subwoofers are compact and don't take up much space in your vehicle. Although powered subwoofers can be very effective bass producers, their smaller drivers and amplifiers may not provide all the sound power you want if you're looking for really powerful bass. On the other hand, their relative ease of installation and small size make them a great addition to the factory stereo system. You'll also find vehicle-specific subwoofers, either with or without a power connection. These subwoofers are designed to fit unobtrusively in many cars and are often color-matched to the vehicle's interior. Like the active subwoofers just mentioned, they may not be the best choice if you are looking for really big bass, but for most listening needs they are more than adequate without taking up much space in the interior.