Car Audio Buying Guide

Car audio improvements can range from modest upgrades to a complete overhaul. While the sky may be the limit when it comes to the ways you can enhance the audio in your car, even modest upgrades can go a long ways towards improving your car audio.

The stereo receiver

Referred to as the receiver or simply the car stereo, this piece is the heart of your car audio system. It acts as the centerpiece, connecting all the various parts of your car audio system and acting as the interface. Receivers may include the tape player or CD player, radio tuner or perhaps the controller for a multi-disc CD changer. More recently, receivers also include interfaces for portable music players, connectors for HD or satellite radio and much more.

As so many people embrace the latest generation of portable music players, so too are receivers improving their support for those players. Some receivers including USB interfaces or SD card slots to let you easily carry music from your computer to your car; for a more complete integration, look for a receiver with a docking interface for your specific model of portable music player; you might just find a receiver that can let your browse and control your music player just as easily as when you're sitting at your computer.

An important criterion in receiver selection is the power output to the speakers. Receivers and speakers work together best when their RMS (or, in layman's terms, sustained) output wattages match; if the receiver overpowers the speakers, they're likely to blow out; if it under-powers the speakers, you'll likely to hear distortion or just poor sound quality, and the speakers may be irreparably damaged. While exact RMS wattage matching is ideal, well-constructed speakers can handle discrepancies of a few watts, either too high or too low.

For people looking to do a more drastic overhaul of their car audio system, you'll want to carefully select your receiver to give you the exact inputs and outputs that you need. Look for a dedicated subwoofer output with a low-pass filter to get the best results from your subwoofer. Also, look for a receiver with the level of dynamic control that you'll want. If you'll be powering all of your speakers with external amplifiers, then you can safely ignore the output power of the speaker connections.

After-market speakers

As a rule of thumb, the car speakers that come with your new car are far from the best speakers available. Upgrading the speakers can give remarkable results in improving the audio quality inside your car. If you're planning on using the existing receiver, then you'll need to pick speakers that both fit your car and whose RMS wattage handling closely matches the RMS output of the receiver.

Your typical factory car speaker is a two-way speaker, meaning that there are two separate drivers (also known as speaker cones) in each speaker: one for reproducing the lower frequencies, another for reproducing the higher frequencies. Any speaker driver is best at reproducing a specific range of frequencies; smaller speakers are better for reproducing high frequencies, while large speakers are more adept at reproducing lower frequencies. (This is why subwoofers are generally so large, often as much as eighteen inches across: They're built to handle the lowest frequencies.) Three-way speakers take this notion one step further by having three separate drivers inside of each speaker, with each driver only handling the range of frequencies that it's best at. This gives you sound that is both clearer and more powerful.

When it comes to choosing the exact size of your speakers, you'll want to pay attention to the sizes of your existing speakers. Many factory speaker systems include either 5.5-inch or 6.5-inch speakers in the front door panels and either 6.5-inch or 6 by 9 inch-speakers in the rear speaker panels. If you're planning on replacing the speakers yourself and you want the fewest complications, get speakers of the exact same size as your existing speakers -- and, just as importantly, check the depth of your new speakers to make sure they'll actually fit in the existing speaker enclosures.

The subwoofer

Once you're experienced car audio with a subwoofer, it can be difficult to ever go without one again. A subwoofer completes the aural coverage that even a great pair of speakers just can't match; after all, even 6 by 9 inch speakers can't reproduce as low of frequencies as the right subwoofer can. Receivers are unlikely to be able to power a subwoofer; you can find subwoofers that include their own power, but otherwise you'll need to look into an external power amplifier. Again, you'll want to match the RMS wattage output of the amplifier with the RMS power handling of the subwoofer. Also, if you're going to purchase a stand-alone subwoofer driver, you'll need to look for an enclosure the subwoofer drivers. (Many car audio enthusiasts build their own subwoofer enclosures, as the enclosure is basically just a wooden box that holds the driver; however, building an air-tight enclosure that can handle the subwoofer's vibration is not a task everyone will want to take on.)

When you start looking at installing your own subwoofer, electrical concerns arise that you generally don't see with other speakers. For example, subwoofers and power amplifiers are often capable of outputting power at different resistance levels, such as two ohms, four ohms or eight ohms. A power amplifier can produce higher wattages at lower resistance levels; however, the subwoofer driver must be able to handle that same RMS wattage at that specific level of resistance. Just ask anyone who's ever accidentally set their amplifier to two ohms then output twice the wattage that their subwoofer could handle because it only supported four ohms; the smell of burnt speaker isn't one you quickly forget!

If your new subwoofer and power amplifier seem to be causing some anomalous behavior in your car's electrical system, such as your headlights dimming right at the moment of a big bass hit, you may need a capacitor to smooth out the power requirements on your car's electrical system. Capacitors (often just called caps) act something like a battery, storing up electricity when the subwoofer's power demands are light then providing large bursts of electricity when the subwoofer calls for it.

Once you start looking at power amplifiers to provide multiple hundreds of watts, you may start providing a burden on your car's electrical system that it's not designed to handle. Your car's electrical system generates a steady stream of electricity, but it also uses that electricity to perform tasks like powering the receiver, powering the car's on-board computers, powering the windows and so forth. Ultimately, your car's electrical system is constrained by the amperage that your alternator can produce; if your new power amplifier exceeds this amperage draw, you'll quickly start seeing blown fuses, and your new subwoofer may go silent until the electrical system is able to produce the power that it needs. Fortunately, most power amplifiers have a gain control that you can turn down to decrease the electrical draw on the car's electrical system. If you want to research this further, your car's shop manual will often detail the total power that your car's electrical system can handle and how much the various components in your car will draw.

Effects processors, equalizers and other audio equipment

Many audiophiles love to tweak the sound of their car audio system until it sounds exactly how they want it. Even if you don't consider yourself an audiophile, you can still get great results from the various sound processors that you can add to your car audio systems. A simple multi-band equalizer lets you fine-tune the sound of your stereo until it suits your ears perfectly. Other units can do more elaborate types of audio processing, such as units that help you tune your car audio system to the precise acoustics of your car's interior.

Connecting your components

If you're simply replacing existing speakers, then you'll probably be able to use the existing speaker wires to connect your new speakers. Even if you are replacing your receiver, you can often find a wiring harness that acts as an adapter to let you easily connect the existing wiring to your new receiver. If a harness isn't available for your exact setup, you can still run the individual wires from your car to an adapter connector that nearly every receiver comes with.

If you're doing a complete overhaul or you're adding a subwoofer, then you'll want to put some more thought into the wiring. High-wattage amplifiers need a lot of electricity, so you'll want to use lower-gauge wires than the original wiring. (In the case of wire gauges, a lower gauge number means a thicker wire -- so, for example, an 8-gauge wire will be thicker wire than a 12-gauge wire, and therefore able to carry more electricity.) Most factory stereo systems use 16-gauge and 12-gauge wires for everything, but you'll probably want to use 8-gauge or larger wire to power all but the smallest amplifiers. When in doubt, check with the amplifier's manufacturer or the amplifier's installation guide to see what gauge of wire they recommend.

In addition to the wiring that powers the amplifier, you may also want to upgrade the wire that carries the audio signal from the receiver to the power amplifier. You can get a cleaner signal by using wires with strong insulation; this is all the more important because your new power wiring may put off a lot of electrical noise as they carry large amounts of electricity. In addition to insulation, some cables use wiring that's been chemically treated to increase transmission speed, helping you get the most precise audio from your system.

When you're installing this new wiring, you'll want to have other accessories on hand, such as spade and flat connectors (depending on what type of connector your new amplifier uses), in-line fuse holders, battery terminals designed to connect the gauge of wiring that you're using and so on. Again, check with the power amplifier's installation guide or with the manufacturer to make sure you have all the accessories that they recommend.