Car Tech 101: Audio-System Basics

Car Tech 101: Audio-System Basics

What You Need To Make a Sound Decision on a Car Stereo System

Automotive sound systems are more complex now that portable media players, hard-disk drives and smartphones are along for the ride. But the basic radio/speaker setup hasn't drastically changed, even though more speakers and more amplifier power have been added over the years.

It can still be difficult to decide what's right for you and to comprehend all of the audio features available. As part of our Car Tech 101 series, we've put together the following information on modern car audio systems to help you while shopping. And since we can't cover every technology in a single article, check out the separate stories on media-player integration and Bluetooth audio. If you want more detailed information on such individual components as the radio, speakers and amplifier, read our series, "Understanding Car Audio Systems."

The goal of this article is to prepare you for the car audio systems you'll encounter on the showroom floor. Before visiting a dealer, please check out "How to Test-Drive a Car Audio System", and take our Car Audio System Tech Checklist with you to the dealership. Finally, this story, "How To Tech-Test Drive — Without Dealer Interference", gives tips on how to avoid hassles at a dealership when you're testing any consumer technology in a vehicle.

Head-Unit Evolution
Car radios are called "head units" in car-audio lingo. They once came in two basics sizes: DIN and double-DIN. A double-DIN head unit is twice the height of a standard single-DIN unit and usually incorporates a large display for a navigation system.

Some car audio systems no longer employ a traditional one-piece DIN head unit. The in-dash components may be spread out, with the CD drive at the bottom of the dash, the display at the top and audio controls in between. Controls can include a touch-screen interface or physical knobs and buttons, or some combination of the two. Regardless of the size of the radio or layout of the components, make sure that the audio system is easy to operate, especially while you're driving.

All car audio systems have some form of a display. Screen size dictates how much information can be displayed and how easy it is to see at a glance. Find out if the display shows complete artist and song information while you're listening to satellite radio or a media player, for example. It can be frustrating if title and artist data is missing or if you have to press a button several times to get it.

Another important consideration is the available audio sources. Currently, AM and FM radio and a disc-based format such as CD and DVD are standard. Many stock systems include satellite radio. More automakers also now offer HD Radio, a form of AM and FM that provides better reception and more features. Check out the video and story on HD Radio for more on the various radio formats available for the car.

Radio Features
All car radios have basic features such as seek and scan tuning and the ability to save favorite stations as presets. But the tuning method varies. Some carmakers use traditional knobs and others use buttons and switches. Radio displays also differ, with some mimicking an old-fashioned radio dial and others only showing a station's frequency. Many head units have Radio Data Service (RDS) that shows artist and song information. It can also group stations by category so that they're easier to find.

Satellite radio groups individual channels by category. Check how easy it is to quickly tune to the categories and channels you like. Some satellite radio stations will also alert you when a favorite song is playing on a channel. And since satellite radio has explicit content that you won't find on AM and FM, you have the option of setting parental controls.

Recent GM and BMW vehicles have a time-shift feature that stores live-radio content to a hard-drive buffer, similar to digital video recorders offered by some cable and satellite TV providers. In BMWs, you can skip back during a live broadcast if you want to hear a song or segment of programming again. GM vehicles with this feature record radio content for a certain time period even after the engine is turned off.

CD and DVD Features
Most car audio CD players have basic features such as play/pause, skip forward/back, fast-forward/rewind, repeat and random playback. Most will also play MP3 files burned onto recordable discs. Some cars have a combination CD/DVD drive that can play both types of discs. A DVD can hold many more MP3s, and some systems with a large in-dash screen can play DVD movies when the car isn't moving.

Some systems play DVD-Audio discs, a format that provides better sound than CD and offers multichannel playback. DVD-Audio never caught on in home audio, but several automakers continue to offer it, including Acura, Cadillac and Chrysler. In some instances, a system will play DVD-Audio discs but not in high-resolution, multichannel surround. Instead, the head unit will "down mix" the audio to two-channel stereo.

Decline of the Disc
iPods and MP3 music files have made it so convenient to carry tons of tunes into the car that many people no longer want to deal with cumbersome discs. Most automakers now offer some way to integrate a portable media player into a car's audio system and play music files loaded onto a USB "thumb" drive. Read more about these options in the Car Tech 101 article on music-player integration.

Bluetooth audio is another feature that's gaining popularity. The technology wirelessly streams music from a compatible device to a car with Bluetooth audio. And if you have an Internet-connected smartphone with the feature, you can stream Internet radio stations like Pandora. For more, check out the story Wireless Streaming Audio: Bluetooth's Second Act.

A hard-disk drive (HDD) is another music source available in some vehicles. You record music files to an HDD from CD, a USB thumb drive or both. The system catalogs files in a format similar to the one used by an iPod. Many HDD systems also allow you to create playlists repeating tracks or albums. And you also can choose to play tracks in random order.

Extra Features
To combat ambient noise in a moving vehicle, automakers employ various digital signal processing (DSP) technologies. A common one raises the volume relative to the speed of the vehicle and the amount of road and wind noise. The effect can be disconcerting in stop-and-go driving as the volume yo-yos, but you can usually turn the feature off.

Automakers also employ DSP such as Dolby Pro Logic II and Harman's Logic7 to give stereo recordings a surround-sound effect and provide a greater sense of space. DSP also can optimize the sound for the driver, front passengers or all occupants. Every system offers basic tone controls such as bass, treble, fader and balance. Others provide midrange and subwoofer-level controls for further fine-tuning of the sound.

Some of the audio-system features you'll want to look for have nothing to do with sound, but make operating the system easier. Steering-wheel controls allow you to turn the volume up or down, skip forward/back on a CD, switch radio stations and change audio sources without removing your hands from the wheel or your eyes from the road. Voice activation lets you control aspects of the audio system by pressing a button on the steering wheel and speaking a command.

Trust Your Ears
You'll find more detailed information about speakers and amplifiers in the series "Understanding Car Audio Systems." And while more speakers and power (measured in watts) create better sound, it's a rule of thumb rather than an absolute. Stock systems that use as few as eight speakers can sound really good, while high-end systems that have 16 speakers aren't necessarily twice as good.

Don't let a fancy brand name sway you when considering a factory audio system, especially if it's an extra-cost option. Just as you can't count on the number of speakers or amount of power to tell you how a system performs, you can't rely on a brand name to ensure great sound.

Just as a car's exterior styling and interior comfort comes down to a matter of personal taste, the sound of an automotive sound system also is subjective. Bring your own music to audition a car system. Judge how it sounds, how easily the system operates and which features and sources are available. The combination of your tunes, your ears and a car audio system that meets your needs will let you and your car make beautiful music together.

To find a dealership that knows how to treat shoppers right, please visit's Dealer Ratings and Reviews.

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