Home vs Car Audio Subwoofer: What's the Difference?

If you need a car audio subwoofer to help improve the quality of sound in your vehicle, you may have noticed that there are many different types in varying price levels. In fact, choosing a subwoofer can sometimes be confusing and difficult; therefore, it leads many people to ask why they can't simply use a home subwoofer in their car. Well, the answer is you can use a home subwoofer in the car. However, it takes a bit of skill to convert the speaker, and it isn't always the best idea simply because of the design differences in the two types of speakers.

Active Versus Passive Subwoofers

When you hook up a subwoofer to your home audio or home theater system, you will probably notice that you must plug the subwoofer into an electrical outlet. This is because most home subwoofers have a self-contained amplifier used to power the subwoofer only. In most cases, it is more cost-effective for the manufacturer to include a separate amplifier in the subwoofer, rather than install an amplifier in the receiver that handles the additional input channel. These types of subwoofers that have self-contained amplifiers are called active subwoofers.

On the other hand, most (although not all) car subwoofers are what are known as passive subwoofers. Car subwoofers are usually wired to an external amplifier used to drive the speaker. With car subwoofers, this is done not too much to save money in the manufacturing process as it is to allow owners of subwoofers to choose an appropriate power level amplifier to drive the unit. The amount of power required to adequately drive a car subwoofer will depend on the size of the vehicle as well as how much volume the owner wants in the bass.

Speaker Efficiency

Another primary difference between a car and home subwoofer is the efficiency of the speaker. In general, home subwoofers are usually much more efficient than their car counterparts. The efficiency of a speaker is simply how loud the speaker is at a given wattage power level. For instance, it is not uncommon for a home-use subwoofer to create around 90 to 95 dB of sound when driven by 1 watt of power. On the other hand, most car's subwoofers will generally require much higher amounts of wattage power to achieve the same decibel listening level.

The reason for the efficiency differences in the two types of speakers is quite simple; home speakers are designed to push more air and produce sound in much larger listening areas than are car subwoofers. The cabin of even the largest car or truck is usually much smaller than the listening area of a living room or other room where a home entertainment system is installed.

Impedance Values: Differences in Resistance

One of the most basic differences between all types of home and car speakers is the impedance rating (Ohms) or resistance rating of speakers. In most cases, car speakers will be rated at four ohms while home speakers are almost always rated at eight ohms. The ohms rating of a speaker is the amount of resistance that the speaker offers to the current being supplied by the amplifier. Theoretically speaking, a speaker that offers lower resistance, or ohms rating, will allow an amplifier to produce higher wattage levels with lower amounts of electrical current. This is particularly important in a car because the car battery can usually only produce between 12 and 14 volts. However, lower impeding or ohms values do allow for more crosstalk, noise and distortion. This is why home speakers usually use an 8 ohm impedance value.