Speakers come in three cone sizes. They are called tweeters, midranges and woofers, and they play the high, middle and low frequencies, respectively. Subwoofers, or subs, are so-named because they handle the sounds below the normal operating range of a woofer.
The job of a subwoofer, which typically has a cone diameter of 8" — 15", is to reproduce those last few octaves of music that are otherwise lost in a typical car audio system. The largest speaker you'll find in most car sound systems is about 6½'' in diameter, and that's just not big enough to play true bass notes.
Choosing a subwoofer
One look at the wide range of prices among subwoofers will tell you that not all subwoofers are alike. So how do you pick a good subwoofer? Listen to it. Here's how we recommend going about choosing a subwoofer:
- Bring some of your favorite music to a store.
- Decide which kind of enclosure (box) is best for you—bandpass, sealed, ported or tube.
- Make sure you listen to the system at the levels you want.
Boxes/enclosures
Each type of enclosure is designed to be used with a particular type of subwoofer and vice versa. It is important to choose a subwoofer that's designed to work with the type of enclosure you want.
Sealed
Sealed or "acoustic suspension" boxes are the simplest and smallest sub box designs. As the name implies, sealed boxes are airtight and use the air trapped inside to act as an air spring against the subwoofer's cone as it moves in and out.
Ported boxes tend to be a little larger than sealed enclosures. These boxes are named for their most obvious physical trait—a tube that allows air to move in and out of the enclosure. Ported enclosures represent a good compromise between the small size and accuracy of an acoustic suspension enclosure and the efficiency of a bandpass box.
Bandpass box
In a bandpass box, the woofer or woofers are completely enclosed inside the box and all the sound you feel and hear is radiated through the port(s) or tubes that allow air to move in and out of the box.
Tubes
Unlike the other box types we've mentioned here, tubes almost always come with a subwoofer already built-in. Plus, many of tubes come with their own built-in amplifier. Remember, you need three things to add bass to your car: a subwoofer, an enclosure and an amplifier. Tubes often come with all three.
Vehicle-specific
The secret fifth option is vehicle-specific enclosures. Because many people don't like the idea of sacrificing space in their trunks even for better sound, the industry has come up with subwoofer system enclosures that fit in the unused nooks and crannies of popular cars and trucks.
