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Capacitors are used in most electronic products, and it’s common to see many of them populating a circuit board. These cylindrical devices store power the way a reservoir stores water. So when a circuit needs a bit of juice, the cap releases it. A capacitor is able to deliver power more rapidly than the car’s charging system because the power capacitor has a lower internal resistance, which allows it to quickly discharge.

In the early 1990s, car audio sound-off competitors started adding large capacitors to their sound systems to provide instantaneous power when peaks in a musical passage demanded it. Before long, car audio-specific capacitors became available to the masses, and now they are a common sight in most high-end systems Capacitors are rated in Farads, which is a measure of how much power they can store. The rule of thumb is to use 1 Farad of capacitance for every 1,000watts of power. So if you have a 500-watt system, you would need a 0.5-Farad capacitor.

Capacitors are available in Farad ratings ranging from 0.5 up to 40 for extremely high-powered systems, and vary in price from $75 for a 0.5-Farad cap to more than $500 for a large-Farad version. Besides Farad rating and shape, capacitors also differ in features, with some sporting built-in digital voltage meters and power-distribution blocks. You can buy a capacitor from most car audio retailers, and they’re available online from e-retailers such as Crutchfield (www.crutchfield.com).

You probably don’t need a capacitor if you have a modest system without a subwoofer, but you could probably use one if your system includes at least one subwoofer. If you have several amplifiers and multiple subwoofers, adding a cap or two can definitely improve your system’s performance. Whether you need a capacitor also depends on how much current your amplifiers draw from the vehicle’s charging system as well as the type of music you listen to. If you primarily listen to bass-heavy rap music and your headlights dim every time your system hits a bass note because of the strain on your car’s charging system, a capacitor could help. (You should also have your car’s electrical system checked to make sure it’s up to snuff, however.) Or if you think the total current draw of all of the amplifiers in your system starts to exceed the capacity of your car’s alternator, you’ll probably want to add a cap.