Shop for car audio

Satellite radio

The XM Mini-Tuner can be used with car stereos.

With the advent of XM and Sirius satellite radio (possibly soon to be the same company), drivers have a source of commercial-free, on-demand radio with a far superior sound quality to that of AM and FM radio. While a minority of stereo head units, such as Alpine's CDA-9820XM, come with a built-in satellite radio tuner, most stereos now come "satellite radio-ready", which means that they can be used to play satellite radio with the use of an add-on XM or Sirius receiver plus a satellite radio subscription. Some car stereos can be hooked up to generic satellite radio tuners, such as the XM Mini-Tuner, eliminating the need to buy a dedicated module and separate subscription for the car.

HD radio

The JVC KD HDR1 has a built-in HD radio tuner.

The other recent advance in in-car radio has been the gradual proliferation of HD radio (sometimes referred to as high definition or hybrid digital radio). HD is a digital broadcasting technology that makes use of the existing FM spectrum to send a digital signal along with the traditional analog signal. Radios with built-in HD receivers sort through the multiple signals and reproduce the original broadcast without the multipath distortion associated with standard analog FM and AM reception. (Multipath distortion happens when a radio signal is picked up by the receiver numerous times, and is particularly problematic around high buildings, which reflect signals and make them bounce around.)

To date, there are only a handful of car stereos on sale that come with built-in HD radio tuners. Examples include JVC's KD HR1 and the Alpine DVA-9956.

More common are stereos that come with the capability of picking up HD radio via add-on receivers. These include single-DIN stereo receivers such as the JVC's KT-HDP1 is a universal device that connects to any FM-capable stereo to play HD Radio.

USB and SD cards

The Clarion DFZ675MC features an SD card slot on its faceplate.

Some stereos, such as the Blaupunkt SD48 and the Jensen VM9512, come with integrated SD card readers. For those who want to play SD card files through USB-enabled car stereos, adapters are available.

Bluetooth

Another option for transferring audio to your car stereo is by a Bluetooth radio connection, which can be used to stream music from portable audio players or cell phones with the advanced audio distribution profile (A2DP), often called Bluetooth audio. Some stereos also include the more sophisticated audio/video remote control profile AVRCP, which lets drivers play, pause, and search for files on a Bluetooth-connected device by using the stereo faceplate controls.

Sony's Pioneer DEH-P9800BT.

Auxiliary-input jacks

The most basic solution for in-car iPod playback is a generic line-in jack and patch cord, which enables drivers to stream music from their players via the stereo to the car's speakers. Some stereos, such as the Sony MEX-BT2500, have auxiliary-input jacks built in to the front of their faceplates to enable drivers to play content from iPods, Zunes, and other digital-audio players through the car speakers.

When playing audio via an aux-input jack, drivers are still required to use the digital-audio player itself to select and control all music playback. The same is true for connections made via FM transmitters, which plug directly into the player and broadcast the iPod's audio to the stereo, and for old-school cassette adapters.

Single-DIN systems

For those looking for a greater degree of control over their iPod libraries when behind the wheel, there are a wealth of stereos that feature an "intelligent" or "full-speed" USB iPod connection, which transfers information from the iPod to the stereo's display itself and gives the driver full search and playback control via the stereo's faceplate buttons. Technically, USB-compatible systems will produce a better sound quality than auxiliary-input jacks because there are fewer connections on the way to the speakers. Stereos with a USB connector let you plug in a USB key filled with MP3 files, and the stereo will use the key as an audio source, just like a CD. With an auxiliary input, you are playing the music on your MP3 player, then running its output into the stereo, where it gets amplified again, as opposed to the single amplification step with the USB key. In reality, you probably won't notice a difference in audio quality, because it will be minimal.

The challenge for single-DIN stereos with intelligent iPod connections is to present a user-friendly means of navigating iPod libraries. Single-DIN stereos don't have the luxury of touch screen systems found in many double-DIN systems, and so, as with MP3 discs, the presentation and navigation interface for iPod tracks is a critical factor in their usability.

Sony's CDX-GT610UI

Among the single-DIN-size stereos that we have seen that do a reasonable job of transferring iPod control to the driver are the JVC KD-PDR30, which all come with iPod connections as standard. With the Sony CDX-GT620IP, for example, drivers can select songs according to artist, album, or playlist. In iPod mode, the stereo's single-line LCD display shows information on artist and album, track name, or track number, according to the user's preference. Although the display shows only eight characters of each information tag, a dedicated SCRL button scrolls the information, enabling the curious driver to get all the relevant information. An option in the setup menu also enables users to configure the display to automatically scroll tag information when a new source, album, or track is selected.

If iPod connectivity is your priority, however, then there is one system that stands head-and-shoulders above the competition in the single-DIN category. The Alpine iDA-X001, designed with input from Apple, is a dedicated in-car iPod interface. Not only does it have a wheel that mimics the movements of the iPod controller, but it also provides menus in the same fonts as the iPod itself, and even displays album art for tracks on fifth-generation iPods.

The iDA-X001 is the first car stereo we have seen that has no internal moving parts. The single-DIN-size stereo comes with a range of features that gives drivers direct control over the songs in their iPod libraries, including a spring-loaded jog wheel for browsing through iPod libraries; an alphabet search function inspired by newer iPods; and a bright, 320x240-pixel TFT screen for displaying album art and iPod menus.

Touch screen systems

For systems with touch screen LCD display, recreating the iPod experience is easier, and many double-DIN-size stereos feature a virtual version of the iPod wheel or the iPod screen itself. However, more real estate does not necessarily mean a more user-friendly iPod experience. When evaluating the usefulness of these touch screen iPod interfaces, one of the important factors to consider is ease of scrolling through digital-audio libraries: if you have an 80GB iPod connected, then you will not want a system that requires you to search through songs one--or even six--at a time.

The Dual XDVD8182 and the Pioneer AVIC-Z1 are examples of systems with cumbersome and labor-intensive iPod interfaces.

Searching through iPod tracks on the Dual XDVD8182 can take forever.

When using the Dual XDVD8182's touch screen to navigate iPod libraries, for example, the only way to browse tracks is by pushing the up or down arrows (to see each name one at a time) or by pressing the File button that allows you to skip forward six entries at a time. As an example of how time-consuming this method of browsing is, it took us more than 120 presses of the File buttons to get through the list of artists in our 4GB iPod Nano. As with the Dual system, the Pioneer AVIC-Z1 only allows users to scroll through iPod entries five at a time; with 80GB of songs loaded on an iPod, getting to the bottom of the list will take hours.

Systems that do a good job of reproducing the iPod interface retain the simplicity of the player itself and give users a means of quickly navigating large libraries. Two such systems we have seen are the Alpine IVA-W200 and the Clarion MAX675VD./p>

The IVA-W200 does a good job of offering a flexible range of control options for iPod music: users can select tracks by the artist, the song title, the album, or the playlist. The IVA-W200 screen displays full tag information for each track, and its basic text format and lack of fancy graphics enable drivers to read the information at a glance. To get through large iPod libraries, the IVA-W200 features a touchable search bar, which enables drivers to quickly skip through the alphabetized list of tracks or artists.

With the Clarion system, drivers are presented with an iPod dashboard on the system's bright LCD touch screen display, from where they can select tracks according to the usual iPod categories (podcast, artist, album, playlists, genres), and can search within those categories. Like the Alpine IVA-W200, the system has a user-friendly one-touch scrolling feature for searching large music libraries.

Bluetooth hands-free calling

The Sony MEX-BT5100 has a built-in Bluetooth receiver.

Most Bluetooth applications require the purchase of add-on Bluetooth receiver modules, which enable calls to be routed from a connected cell phone through the stereo to the car's speakers. Add-on Bluetooth kits often include an external microphone, which can be attached to the car's dashboard or sun visor. Some systems do come with Bluetooth calling capabilities built in.

Sony's XDMA6700 also features a built-in microphone and a unique hard-button keypad, although curiously requires an external module to connect to Bluetooth phones.

When evaluating a Bluetooth-enabled stereo, it is important to take into account the ease of making and ending calls and the quality of the built-in mic. Also, many add-on modules are clunky boxes that require a substantial amount of room behind the dashboard or in the globe box.

GPS navigation

As this is primarily a guide on car stereos, we won't go into too much detail on the technical details of GPS: those looking for an in-depth analysis of GPS can check out our GPS buying guide. However, navigation does deserve a mention as many double-DIN aftermarket car stereos (and some single-DIN ones) come with navigation as an optional or standard, integrated feature. Most touch screen and LCD in-dash audio/ video players come with navigation as a standard feature or offer it as an option via an add-on GPS module.

Among the former group, the Pioneer AVIC-Z1 and the Eclipse AVN series are state-of-the art examples of navigation-enabled stereos, as both offer detailed maps, text-to-voice route guidance, and the option of real-time traffic information. The AVIC-Z1 even comes with the added benefit of a voice-recognition system--something that we usually see only in high-end factory-installed systems.

The Pioneer AVIC-Z1 combines audio/video playback with GPS navigation.

Other in-dash touch screen navigation systems include the Alpine Blackbird portable navigation device.

As with factory-installed systems, ease of programming is a key feature to consider when shopping for an aftermarket in-dash navigation unit. Processor speed and refresh rate are also important factors: you don't want the system to take three or four seconds to refresh between each letter of a destination or when adjusting the level of zoom.

Because navigation systems usually feature maps, which require lots of real estate, single-DIN systems don't often attempt to offer navigation. One notable (and unfortunate) exception is the KD-NX5000, which, despite its size, integrates a bright, 3.5-inch color LCD screen to guide drivers around.

The JVC KD-NX5000 is a hard-drive-based system, which means that its GPS database is stored on an internal drive rather than read from a DVD-ROM. The advantages of hard-drive-based GPS systems are numerous: they don't require a separate disc drive for navigation data; they are far quicker at calculating routes and refreshing maps; and they can often be used to store media files as well as their map information. Expect to see more hard-drive-based GPS units hit the market as hard drives become more rugged and resistant to extreme temperatures.

Power rating:

Always use the RMS rating (measured in watts) rather than the peak power rating. RMS is an indication of a system's continuous power used for consistent output rather than its maximum capability.

EQ controls:

Most stereos come with some kind of equalizer for enabling drivers to tweak the bass, treble, and midrange bands. Advanced systems have four-, five- or even seven-band equalizers, and give the driver control over the center frequencies for each band for the smallest tuning tweaks.

Crossovers and high- and low-pass filters:

Some stereos such as the Eclipse AVN 6600 feature user-configured crossover settings, which let drivers set the frequency at which audio signals are sent to a specific band. Adjustable high- and low-pass filters work in a similar way by reducing or blocking output that is under or over a specific frequency before it gets to selected speakers. For example, a high-pass filter might allow only frequencies over 2000Hz to play through the tweeter speakers. In this way, the speakers are protected from damage and only those sounds intended for a certain acoustic range are amplified, leading to a more refined output.

The Alpine AVN6600 features a three-band equalizer.

For those audiophiles who want to route their audio through an external amplifier, the preout connections are a key consideration when shopping for the stereo head unit itself. Preouts are RCA connections required to connect your stereo's output to an external amplifier. Advanced systems will have more powerful preout configurations of four, five, or eight volts, which deliver a better signal to the amplifier and result in a clearer, brighter output. Basic stereos will come with one or two pairs of RCA preouts (allowing a limited number of amps to be connected), but advanced systems can have up to five.