Complete Your Car Audio Sound With a Subwoofer

Keep these tips in mind when shopping for a subwoofer

Low-frequency sounds are a major component of good sound. The quality of a sound system hinges on its ability to replicate the low notes as well as the highs. Some types of music benefit from a great subwoofer more than others, but adding quality bass to a stereo system brings the music to life.

Whether you're thinking about adding a subwoofer to an existing speaker setup or building something from the ground up, here are some important details to keep in mind.

Close up of kicker subwoofer
null0 / Flickr / CC BY 2.0

Size Matters

The size of the subwoofer is one of the main factors that determine how loud and how low it can go. As a general rule of thumb, bigger subwooferss produce better bass, so keep that in mind while looking for the ideal unit.

Space is also a concern in automotive sound systems. It's critical that you take measurements of your available space before you start shopping. If you're looking for the boldest bass you can get, then go for the biggest subwoofer that will fit your vehicle.

Trapping the Sound in an Enclosure

While the size of the subwoofer is important, the type of enclosure you choose may have a bigger impact. The enclosure, which is usually referred to as a box, is just that: a box that contains the subwoofer. The three main types of enclosures are:

  • Sealed
  • Ported
  • Bandpass

If you want bass that is exceptionally deep and doesn't sound like your subwoofer is farting, go for a sealed enclosure. In some cases, a smaller subwoofer in a well-built, sealed enclosure will produce deeper bass than a larger subwoofer in an open enclosure. This type of enclosure is great for tight, accurate bass that won't shake your fillings loose.

Ported and bandpass enclosures are typically louder but not as deep. If you listen to music that demands extremely loud bass, and you don't care much about accuracy in the low-end frequencies, consider one of these enclosures.

The other option is to choose a subwoofer that is designed to work without an enclosure. These subwoofers are typically mounted to a board installed inside the trunk. The trunk has to be relatively airtight because it acts as a de facto enclosure.

Power, Sensitivity, Frequency, and Impedance

While the size of the subwoofer and type of enclosure are important, the specs you should look into are the RMS value, SPL, frequency range, and ohms.

The power level (RMS) refers to the power handling characteristics of the subwoofer. A higher RMS value means more bass. A high RMS value is useless without anything to power it, though, so you'll need a head unit or amplifier that matches (or preferably exceeds) the RMS of the subwoofer.

Sensitivity, which is expressed as a sound pressure level (SPL) number, refers to how much power the subwoofer needs to produce a given volume. Subwoofers with high SPL ratings don't require as much power to produce high volumes as subwoofers that have low SPL ratings. That means you'll want a subwoofer with high sensitivity if your amp or head unit is underpowered.

Frequency refers to the range of sounds that the subwoofer can produce, so look for a unit on the low end of the scale. However, the sound you get out of a subwoofer depends on the type of enclosure you choose. Since the enclosure can modulate the sounds that reach your ears, the frequency numbers of the subwoofer may not accurately reflect its real-world operation.

To get the most out of your amp and subwoofer, it's important to match impedance. This figure is expressed in ohms, and it refers to the electrical resistance of the subwoofer. Low impedance means the speaker can receive more electrical signals, thereby improving audio fidelity. As a concept, impedance is relatively straightforward, but it gets complicated depending on how a subwoofer is wired, or if it has multiple voice coils, among other variables.