When most people think about a "car stereo," they're actually thinking about the receiver. Also known as the head unit or deck, the receiver is both the brain and heart of your car audio system and the bit that you'll directly interact with from behind the wheel. When you choose a receiver, you're also locking in your available audio sources, features, and the expandability of the rest of your car audio system.
So what should you look for when choosing for a new receiver? Here are the 7 attributes that we consider when recommending a car stereo, along with a few of our top picks to get you started on your search.
The most important bits that you should look for are the audio sources that you most often use.
Do you need a CD player? Will you be using your receiver for DVD playback when parked? Have you ditched discs in favor of digital media? Depending on your answer, you'll have to decide whether to go with a traditional CD-receiver with a slot for your discs, a larger A/V receiver with a color screen, or a mechless receiver that ditches the drive and all of the moving parts that come with it.
Even if you still keep a book of CDs in your car's glove box, odds are good that you or a passenger will want to plug a phone or media player up to your car at some point, so make sure that your new receiver at the very least includes a USB port for MP3, AAC, or WMA playback from flash storage devices and a 3.5mm analog auxiliary input for universal connectivity.
The early adopters' choice: Parrot Asteroid
Completely ditching its optical drive in favor of non-physical, the Parrot Asteroid is one of the most forward looking receivers that we've tested. Though its sometimes-buggy reliance on USB-stored, Bluetooth-streamed, and Web-connected media will appeal mainly to early adopters and tinkerers, this diminutive deck shows much promise thanks to its large (for a single-DIN) color display and Asteroid Market of Android-based applications for navigation and audio streaming.
Apps and smartphone integration
You're a CNET reader, which means the odds are good there's smartphone in your pocket that you'll want your new car stereo to play nice with. Be sure to check out CNET's guides to using your Android phone or connecting your iOS device to the car for details. The broad advice is to look for the "Made with iPhone" badge to ensure that the USB port on your new stereo supports full speed access to your iDevice's media. Users of the iPhone 5S, 5C, or any of the iPads that use the new Lightning connector will also want to make sure the receiver uses a plain-vanilla USB port and not an older 30-pin connector.
Android, Windows Phone, and Blackberry users have no badges to look for. Either pick a receiver that uses A2DP stereo Bluetooth audio streaming for wireless media playback or make use of the aforementioned auxiliary input for the simplest connection.
Heavy users of streaming apps like Pandora or iHeart Radio should look for receivers that feature controls for those apps, putting your custom stations, pause/skip controls, and rating tools in the dashboard, where they can be more safely (and legally) accessed when on the road.
Users who want a more closely integrated app experience should look at app mirroring devices such as Pioneer's AppRadio series and the variety of MirrorLink and MHL compatible receivers from Alpine, Sony, and JVC. Compatibiltiy with these app mirroring systems is relatively new tech and is currently limited to only a few dozen devices, so be sure to make sure your phone is compatible before taking the plunge on a receiver purchase. Parrot's Asteroid series sidesteps the app mirroring trickiness by storing and running versions of its Android-based apps on the receiver itself, but is limited in the number of supported apps.
Check out our list of aftermarket car stereos for app addicts for more recommendations.
Top pick for app lovers: Pioneer AppRadio 2
Pioneer's AppRadio and AppRadio 2 are the first receivers that spring to mind when I think about aftermarket app integration done right. The flagship AppRadio 2 boasts a massive color touch screen and compatibility with dozens of apps for iPhone and Android devices. It's not a perfect solution -- getting the unit to work with a supported Android phone requires the installation of a hardware module and about two or three helper apps -- but until we start seeing MirrorLink building significant steam, AppRadio is king.
Local and satellite radio
Every car audio receiver sold today will feature an AM/FM radio that will tune into your local stations, but you may want to improve on that. Picking a receiver that has built-in HD Radio decoding will dramatically improve the audio quality of local radio stations broadcast in the digital format. You'll also be able to access digital subprograms for stations that support multicasting to increase the amount of available free programming, as well as iTunes Tagging of broadcast songs for purchasing and downloading later.
I'm not a huge fan of the audio quality offered by satellite radio, but frequent road trippers and other drivers who travel long distances may see value in being able to have their favorite radio stations beamed to them from space to anywhere in the country. Sports fans may also appreciate the variety of NFL, NBA, and NHL programming available on the subscription based service. Most new car stereos that are able to support satellite radio will do so via an optional SXV100 or SXV200 SiriusXM Connect module, so be aware that you may need to purchase and have additional equipment installed, as well as paying a monthly or annual subscription.
GPS and navigation
Car audio receivers can do more than just play your music; many can also help to get you where you're going with turn-by-turn GPS navigation. Nearly every recommendation that we make in CNET's GPS buying guide applies here. For those too lazy to click the link, you'll want to look for flash memory-based maps that can be upgraded via a removable SD or microSD card. Traffic reporting is extremely useful and can be had for free over the RDS-TMC band or through the HD Radio tuner.
More than a few of you are already poised to argue that the navigation app on your phone would be superior to an in-dash system and you're basically correct in that assumption. Smartphone navigation apps such as Waze, Google Maps, and Scout stand, generally, head and shoulders above the best aftermarket in-dash GPS receiver that I've tested, offering more up-to-date and accurate maps with fresher traffic data, voice commands, and better destination search.
Best in-dash navigation: Sony XNV-770BT
The Sony XNV-770BT uses a removable navigation module to power its excellent TomTom map software for turn-by-turn directions. This allows the onboard maps to be more easily and more frequently updated. It's a good choice if you must have in-dash nav, but even this combo is easily outshined by the average smartphone. Consider instead paring one of the newer app mirroring receivers with an app like Waze or Scout.
To get the best of both worlds -- the in-dash unit's larger screen and the superior software of a smartphone app -- consider a receiver with some sort of app mirroring functionality. I've already mentioned a few of my favorites above.
Of course, you could also just mount your phone or tablet to your dashboard or windshield for navigation while outputting the audio to your receiver's Bluetooth or auxiliary input -- provided, of course, that your interactions with your smartphone fall within local legal limits.
Physical dimensions, physical controls
With your audio source wishlist locked in, you'll want to consider the physical dimensions and interface of the receiver itself. Primarily, this means deciding between a single-DIN or double-DIN receiver. Single-DIN receivers occupy less space in the dashboard, are less obvious to outside viewers and would-be thieves (particularly models that feature detachable faceplates), and fit into a wider variety of dashboards. Double-DIN models take up more dashboard real estate and often feature large, touch-sensitive displays. If you answered yes to wanting DVD playback, GPS navigation, or app mirroring above, you're most likely ending up with a double-DIN unit in your dashboard.
Consider also the controls on the receiver's face and the software's interface. Touch screens are nice, but let's not downplay the ease of use afforded by good physical controls when you're doing 70-plus mph. Likewise, a confusing interface or a touch screen that's sluggish to recognize your inputs can cause you to spend more time fiddling with the receiver when you should be watching the road. Personally, I like a good physical volume knob over buttons for quick adjustments, but you may prefer a receiver that supports the steering wheel controls on your personal car via an adapter. Steering wheel compatibility varies wildly between the make and model of your car and the model of your chosen receiver, so you'll need to do a bit of research before you buy.
Best on a budget: Pioneer DEH-X9500BHS
The Pioneer DEH-X9500BHS CD receiver features standard CD/AM/FM sources, and also decodes HD Radio out of the box. Smartphone users gain access to Bluetooth calling and audio, USB/iPod connections, and Pandora Internet radio. That's a remarkably wide range of audio sources for a low-cost, single-DIN receiver. Consider the detachable faceplate security, three stereo preamp outputs, and a responsive physical volume and control knob, and it's no wonder that this is one of my favorite budget car audio receivers.
In addition to accepting your audio sources, the purpose of the in-dash receiver is to output that audio to your car's speakers via its internal amplifier. The power of this amplifier is stated in two ways: peak power and RMS. The peak power is measured in watts and is the maximum amount of power that the amplifier is capable of producing. Unless you always listen to you music at the maximum possible volume, you'll want to ignore this number...for now.
Instead take a look deeper into the list of specs for the RMS power rating, which is essentially the amount of power that the amplifier will consistently produce with regular use. The power rating will also include a number of channels that the amp is capable of outputting (usually four: front right and left, and rear right and left) and will be presented something like "25Wx4 RMS" or "52Wx4 max."
Generally, more RMS power is good, giving you more headroom for volume before reaching the limits of the amp's ability, where distortion can be an issue. However, more watts don't necessarily mean better sound; that quality is determined by a variety of factors such as the quality of your audio source, digital signal processing, equalization, the digital-analog converter, and ultimately the speakers. I find that for most stock and reasonably priced aftermarket speakers will perform well with about 25 watts RMS or about 50 watts max per channel, but you'll also want to make sure that your amp's output doesn't exceed what your speakers can handle.
Drivers interested in adding external amplification, powered subwoofers, or accessories should also consider the upgradability of the receiver. Generally, this is determined by the number of A/V inputs and pre-amp outputs found on the rear panel. I like to make sure that there are at least two full-range stereo preamp outputs and award bonus points to receivers that feature a dedicated subwoofer output. I'll be digging more into adding external amplification and subs in a future guide, so stay tuned.
Best for Bluetooth: Sony MEX-GS600BT
The Sony MEX-GS600BT Bluetooth audio receiver rolls hands-free calling and a full array of digital audio sources into one low-profile box in your dashboard. App Remote allows users to quickly jump between listening to on-receiver sources and on-smartphone apps at the touch of a button. Although I didn't find App Remote very useful without a dashboard mount for your phone, everything else about this full-featured car stereo makes it easily recommendable.
Every make, model, and year of car is different, so installation can be tricky. However, nearly every receiver uses a standard wiring harness for connections to your car's 12V power and its speakers. If you plan on doing the installation yourself, you'll need to be able to take your particular car's dashboard apart and remove the stock radio, a wiring harness to connect the new receiver's standard harness to your car, and a mounting kit to hold everything into your dashboard. A rudimentary understanding of soldering or crimping wires is helpful. I'll dig into these details in a future guide on car stereo installation.
Alternately, you could pay a certified installer to do it for you. These days, installation is often cheap and sometimes free.