Bluetooth Car Stereo Basics

Hands-Free Calling, Music Streaming, and More

bluetooth car stereo
Bluetooth car stereos are available from the aftermarket in addition to commonly being integrated into infotainment systems. Image courtesy of JVC America, via Flickr (Creative Commons 2.0)

Bluetooth is a feature that can be found in both original equipment (OE) and aftermarket car stereos, and it’s not limited to any particular car stereo configuration. This wireless communication protocol allows devices to communicate with each other across distances of up to 30 feet, so it is ideal for creating a small, personal area network (PAN) inside a car or truck.

The safety, convenience, and entertainment features offered by Bluetooth car stereos are fairly diverse, but they’re not limited to head units that have the functionality built in. Even if your head unit doesn’t have Bluetooth, you may still be able to take advantage of features like hands-free calling and even internet audio streaming with the right add-on kit.

What is a Bluetooth Car Stereo?

A Bluetooth car stereo is just a car stereo that has built-in Bluetooth capabilities. In most respects, a Bluetooth car stereo is a lot like any other car stereo. Also known as a head unit, since it controls every other audio component in your car, a car stereo will usually include a radio, may be able to play CDs or MP3s, will have either a built-in amplifier or pre-amp outputs, and also connects to the speakers.

In addition to all of that, a Bluetooth car stereo also includes Bluetooth connectivity. This typically allows it to connect to your phone, a wireless earpiece or headphones, and other portable electronics. Many of the best car radios on the market include Bluetooth.

What is Bluetooth and How is it Used in Cars?

Bluetooth is a communication protocol that allows devices like cellular phones and head units to share data back and forth, but some Bluetooth-enabled devices offer more functionality than others.

The specific features that any given Bluetooth car stereo offers are dependent on the profiles that it is designed to make use of, so some head units offer significantly more functionality than others.

Some of the most common features offered by Bluetooth car stereos include:

  • Hands-free calling: This extremely common feature allows you to place calls using a Bluetooth earpiece, a built-in microphone and your car speakers, or your phone's speakerphone.
  • Audio streaming: This feature allows you to stream music, podcasts, and other audio from your phone to your car audio system.
  • Remote app control: This is a two-way feature that allows you to control your phone, or specific apps, with your car stereo.
  • Access to stored contact information: This feature allows you to pull up information from your phone, like your address book, on your car stereo.

Each feature makes use of one or more profiles in the “Bluetooth stack,” so the head unit and any paired devices all need to be on the same page for everything to work properly.

Bluetooth Car Stereos and Hands-Free Calling

While it’s illegal to use a cellular phone when driving in many jurisdictions, most of those laws have exemptions for hands-free calling. And though many cellular phones offer speakerphone options, and a Bluetooth-enabled cell phone can be paired directly to a headset, a Bluetooth car stereo can offer a much more integrated experience.

There are two profiles that Bluetooth car stereos can use to facilitate hands free calling:

  • Headset profile (HSP): Usually found in hands-free calling kits. Offers basic functionality only.
  • Hands-free profile (HFP): More fully-featured. Usually found in Bluetooth car stereos.

HSP is more commonly found in aftermarket hands-free calling kits, while HFP offers deeper functionality. When you pair your cellular phone to a Bluetooth car stereo or hands-free calling kid that uses HSP, it will usually just work like a Bluetooth earpiece and provide very basic connectivity.

When you pair your phone to a device that supports the hands-free profile, the head unit will typically lower or mute the volume when a call is initiated. Since that saves you from having to remove your hands from the wheel to operate the stereo, this type of Bluetooth integration offers a significant level of convenience and increased safety.

Access to Stored Contacts

When a Bluetooth car stereo supports either the object push profile (OPP) or Phonebook Access Profile (PBAP), it will typically allow you to use the head unit to access the contact information that’s stored on your phone.

OPP sends contact information to the head unit, where it can be stored in the memory of the Bluetooth stereo. That allows you to access the information for hands-free calling, but you have to manually resend contacts after updating them.

Phonebook access profile is a little more advanced, in that the head unit is able to pull contact information from a paired cellular phone at any time. That makes it easier to update contact info, but it can also result in an improved hands-free calling experience.

Audio Streaming

Head units that support Bluetooth audio streaming allow you to wirelessly send music and other sound files from your phone to your car stereo. If you have music, audio books, or other content on your phone, a Bluetooth car stereo that supports the advanced audio distribution profile (A2DP) will be able to play it.

Additionally, you may be able to play Internet radio like Pandora, Last.fm and Spotify. And if your Bluetooth car stereo supports the audio/video remote control profile (AVRCP), you can even control the streaming audio from the head unit.

Remote Bluetooth App Control

In addition to controlling streaming media via AVRCP, other Bluetooth profiles can provide remote control over various other apps on a paired phone. Using the serial port profile (SPP), a Bluetooth car stereo can actually remotely launch apps like Pandora on your phone, after which A2DP and AVRCP can be used to receive and control the streaming media.

Bluetooth Car Stereo Alternatives

If your car stereo doesn’t have Bluetooth connectivity, but your phone does, you can still take advantage of many of these same features. The experience won’t be as seamless as a Bluetooth car stereo can provide, but there are a variety of kits and other hardware that will provide you with hands-free calling, audio streaming, and other features. Some of the potential Bluetooth car stereo alternatives include:

  • Bluetooth hands-free car kits
  • Mounted speakerphones
  • Bluetooth audio streaming kits