Comparative ” Wirecutter “. A Bluetooth audio kit allows you to connect a smartphone to a car radio, even if it is not equipped with Bluetooth audio transmission. We have tested devices that are connected to the car radio by audio cable or FM radio waves, from Besign, GOgroove, Avantree, Anker and others. Here are our choices for connecting your phone to your car.

If you want to listen to music or conduct phone conversations through your car’s speakers, but your car isn’t equipped with Bluetooth, a Bluetooth kit is an affordable and effective solution. After testing dozens of models, we think the Besign BK01 Bluetooth car kit, which plugs into your car stereo’s “AUX” jack, offers the best combination of sound quality, ergonomics and features. Below are other choices for vehicles without an auxiliary input, as well as for users whose phone is primarily used for making calls and not for playing music.

Besign BK01 Bluetooth 4.1 Car Kit

A jack audio cable, plugged into the car stereo’s auxiliary input, is the most reliable way to add Bluetooth to your car and produces the best sound. The Besign BK01 is overall the best device on the auxiliary input that we tested. When playing music, it provided us with better sound quality than other equipment. And it produced better quality audio communications, allowing for more intelligible phone calls than many other models, even if the call quality is still inferior to that of a dedicated microphone/speaker handset. Like some competitors, the BK01 allows two phones to be connected simultaneously, and the built-in button can activate Siri or Google Assistant to use voice control.

GOgroove FlexSmart X2

Avantree CK11

Who should use these devices?

If your car isn’t the newest, it may not have a built-in Bluetooth connection, which allows you to stream music from a smartphone, like phone calls. Can’t or don’t want to install a new audio system? Then you have several options for listening to your music and making calls through your vehicle’s speakers. The three most common involve a Bluetooth receiver plugged into the auxiliary input (mini-jack marked AUX), an FM transmitter that broadcasts your phone’s audio on FM radio frequencies for your car stereo to receive, or a microphone/speaker combo independent of the car stereo. The first two options allow you to listen to music or the person you’re talking to on the vehicle’s speakers; the latter incorporates its own audio system and is designed more for phone call quality.

Which type to choose?

None of these devices are perfect, but they’re all portable, inexpensive (much less than a new car radio) and relatively easy to use. Depending on the system you choose, you may have to sacrifice your car’s 12V power supply, a.k.a. the cigarette lighter, although some models give you a powered USB output that can be used to charge other devices. Otherwise, you’ll need to recharge the adapter regularly. While sound quality varies greatly from one type of device to another (the worst ones clearly don’t sound as good as a direct Bluetooth connection to a compatible sound system), all of them will do until you change cars or car stereos. To determine which system is best for your needs, here are a few things to consider:

If your car has an auxiliary input (a regular jack), get an AUX kit. These compact, easy-to-use devices let you control music and phone calls with buttons built into the receiver. And because they use a wired connection to your car stereo, AUX kits offer the best sound quality.

If you don’t have an auxiliary input and want to listen to music instead of making calls, an FM transmitter is for you. It takes the audio received from the phone via Bluetooth and rebroadcasts it on an FM radio frequency. Your car radio can then pick it up. This system adds a layer of potential interference, so it’s more sensitive to static electricity and the sound isn’t as good as with a wired connection, but our first choice offers a particularly reliable connection. Call quality isn’t great: the microphone on these devices can’t be placed in the ideal spot, but music and podcasts sound good. Note that it is best to avoid making a confidential call with such a system: any radio receiver within range of your transmitter, such as the car radio in the front or back, can listen to the sound of your smartphone.

If you don’t have an auxiliary input and value call quality over music, or if you use your smartphone primarily for calling, consider a dedicated handset. Smartphone handsets are compact and approach a true hands-free experience, making them ideal for phone conversations. Some also allow you to control music, pick up the phone or send texts without touching your phone. However, they’re not as good at playing music as their predecessors: often, their sound is just a louder version of your phone’s speaker.

Other options

While a Bluetooth car kit is the easiest and least expensive way to add Bluetooth to your car’s sound system, there are others. If you also want a GPS navigator that can guide you around corners, many models include a Bluetooth link for hands-free calling. But they don’t play music, and they’re usually much more expensive than the equipment in this guide, so we don’t usually recommend them for a Bluetooth upgrade.

If you plan to keep your car for a few more years, you can also upgrade its audio system: this way, you’ll have a Bluetooth connection and, depending on the car radio you choose, useful features like satellite radio, Siri or Google Assistant integration, or even Apple CarPlay and Android Auto. This approach isn’t possible with every car, and it’s more expensive than a simple Bluetooth kit, but the resulting experience is much smoother and you’ll have a new car radio.

If you don’t have an auxiliary input and want to listen to music instead of making calls, an FM transmitter is for you. It takes the audio received from the phone via Bluetooth and rebroadcasts it on an FM radio frequency. Your car radio can then pick it up. This system adds a layer of potential interference, so it’s more sensitive to static electricity and the sound isn’t as good as with a wired connection, but our first choice offers a particularly reliable connection. Call quality isn’t great: the microphone on these devices can’t be placed in the ideal spot, but music and podcasts sound good. Note that it is best to avoid making a confidential call with such a system: any radio receiver within range of your transmitter, such as the car radio in the front or back, can listen to the sound of your smartphone.

If you don’t have an auxiliary input and want to listen to music instead of making calls, an FM transmitter is for you. It takes the audio received from the phone via Bluetooth and rebroadcasts it on an FM radio frequency. Your car radio can then pick it up. This system adds a layer of potential interference, so it’s more sensitive to static electricity and the sound isn’t as good as with a wired connection, but our first choice offers a particularly reliable connection. Call quality isn’t great: the microphone on these devices can’t be placed in the ideal spot, but music and podcasts sound good. Note that it is best to avoid making a confidential call with such a system: any radio receiver within range of your transmitter, such as the car radio in the front or back, can listen to the sound of your smartphone.

How we selected and tested them

We started by reading every device comparison we could find. CNET and PCMag are two of the few places where you can find articles on Bluetooth car kits, and even there, the tests are often several years old. So we also looked at user reviews on Amazon, which are more recent and generally numerous. Whether the product was an AUX adapter, FM transmitter, or external handset, the most important criteria in our search was ease of use, and we wanted to know how close the product came to the experience of an in-car Bluetooth link. With this in mind, we set out to find the most promising candidates for each type of kit.

In making our selection of models to test, and during testing, we focused on the following criteria:

Sound quality: this is by far the most important element of a Bluetooth car kit. There’s no point in being able to listen to music, podcasts or take phone calls if you don’t have clear, audible and pleasant sound, both in reception and transmission. Some Bluetooth handsets are designed specifically for calls, and in these cases we’ve focused more on call quality than music playback.

Music and phone functions: If you want the Bluetooth experience built right into your car stereo, your device must play music from your phone as well as make calls. So we eliminated devices that didn’t offer at least both of these features.

Ease of use: We were particularly looking for models that automatically reconnect to the paired phone when the car is started, and that have clearly labeled buttons and controls.

Power: Most kits use USB chargers that plug into your car’s 12V outlet (aka “cigarette lighter socket”). We eliminated the ones that didn’t leave at least one USB port free when plugged in: if you use your phone to play sound or communicate, it makes sense that you’d want to power it too.

Reputation: these kits are affordable and endless. Amazon sells hundreds of anonymous brands that offer their versions of these products. With that in mind, we focused on manufacturers with a reputation for quality and who provide a reliable warranty.

User reviews: we eliminated products with many negative reviews, as well as those that had accumulated a suspicious amount of reviews in a very short period of time.

If you don’t have an auxiliary input and want to listen to music instead of making calls, an FM transmitter is for you. It takes the audio received from the phone via Bluetooth and rebroadcasts it on an FM radio frequency. Your car radio can then pick it up. This system adds a layer of potential interference, so it’s more sensitive to static electricity and the sound isn’t as good as with a wired connection, but our first choice offers a particularly reliable connection. Call quality isn’t great: the microphone on these devices can’t be placed in the ideal spot, but music and podcasts sound good. Note that it is best to avoid making a confidential call with such a system: any radio receiver within range of your transmitter, such as the car radio in the front or back, can listen to the sound of your smartphone.

If you don’t have an auxiliary input and want to listen to music instead of making calls, an FM transmitter is for you. It takes the audio received from the phone via Bluetooth and rebroadcasts it on an FM radio frequency. Your car radio can then pick it up. This system adds a layer of potential interference, so it’s more sensitive to static electricity and the sound isn’t as good as with a wired connection, but our first choice offers a particularly reliable connection. Call quality isn’t great: the microphone on these devices can’t be placed in the ideal spot, but music and podcasts sound good. Note that it is best to avoid making a confidential call with such a system: any radio receiver within range of your transmitter, such as the car radio in the front or back, can listen to the sound of your smartphone.

Our testing procedure has not changed as this guide has been updated. To evaluate the audio quality and sound clarity of phone calls, we left voice messages with the windows closed and then the windows open while driving on a fast lane at about 85 km/h. We distributed the files of these messages to a panel of Wirecutter editors for them to rate and comment on their sound quality. At the time of the early versions of this guide, we drove a 2013 Toyota Prius C; for the latest iterations, we used a 2006 Honda Civic.

In the latest update, we took a similar approach to testing music quality. To get around the potential quirks of car audio systems, we plugged each kit using an auxiliary input into a Focusrite Scarlett 2i2, our favorite USB sound card, to record a snippet of a song playing over Bluetooth from a phone. Then we shared those files (along with the original file to serve as a blind check) with the Wirecutter editors, who ranked them by audio quality.