Subwoofers

For your low end

By Adam Wilkerson

The dream for any music lover when they pop in a CD or fire up their MP3 player is to feel like they’re sitting right in front of the artist playing the music they love. Whether you like violent guitar riffs or the elegant massaging of ivory keys, accurate reproduction is the key to living that dream. If you can’t feel the beat of the kick drum in your chest or the lazy sounds of the baritone sax in your stomach, perhaps adding a subwoofer to your car audio system will put you back in the front row.

Rerouting Sound

The subwoofer is actually a system in itself consisting of a high-excursion driver, an enclosure, crossover and amplification. This system is responsible for outputting the lower frequencies of a sound track. These lower frequencies, known as bass, are very difficult for the smaller drivers found elsewhere in the vehicle. Properly adding a subwoofer will route the bass away from these smaller drivers allowing them to work more efficiently; reducing harsh sounds and distortion in the mid and upper ranges. A crossover is sort of like a traffic cop, routing the proper frequencies to the best-suited drivers.

Subwoofer Drivers

As you move lower in the frequency spectrum, the sound waves get much larger. To accurately produce these waves you need to move air – and in some cases, a lot of air. This is where the larger driver comes in. These larger drivers are capable of moving enough air for you to “feel” the music and come in various sizes. They measure from 4 to 18 inches.

The type of music you listen to and the amount of space you have should be the determining factors in what size driver will work best for you. Larger doesn’t always mean louder, but larger often means it has an extended range, making it easier to hear the really low sounds. Making the speaker move far enough and fast enough will often require more power than a standard head unit comes equipped with. This is where the amplifier comes in.

Subwoofer drivers are rated several different ways. They will have a continuous power handling, max power handling, sensitivity, frequency response, impedance and other ratings listed in their specifications. It’s important to keep these in mind when choosing an amplifier. Too much or too little power can damage the driver. Match the amplifier’s wattage rating with that of the driver to ensure safe, long lasting use.

The sensitivity rating describes the amount of output it’s capable of producing based on the wattage it receives. In other words, the higher the sensitivity rating, the louder it will play on any given amount of power. Frequency response is the range that the driver is capable of outputting. Again, match amplifier settings to ensure that the driver is only asked to play material that it’s capable of.

Subwoofer Enclosures

To complete the system, you need something to move air in and out of – that is, the enclosure. This will be largely dependent on the space you have and the listening material itself. Drivers will have a recommended enclosure size, often measured in cubic feet, depending on needed frequency response and amount of amplification.

There are two main types of enclosures: sealed and vented. Vented enclosures (also known as ported enclosures) tend to be more efficient, meaning they don’t require as much power to maximize output. They can also be tuned to play lower frequencies, but require a much larger space. A sealed enclosure is a more compact package, but requires more power to achieve optimum response and output.

Subwoofer systems range from multiple driver and amp combinations to simple “plug and play” add-ons. As with any audio device, auditioning is crucial to determining the best system to suit your needs. It’s important to keep in mind the style of music you listen to, how loud you listen to it, the space you have, budget and the sonic impact you desire. A subwoofer isn’t just a loud bass maker, it’s the workhorse of any great car audio system and imperative to hearing music exactly the way the artist intended.