Our editors independently research, test, and recommend the best products; you can learn more about our
review process here.
We may receive commissions on purchases made from our chosen links.
Lifewire / Benjamin Zeman
Answer phone calls with the press of a button
Voltmeter to monitor car battery voltage
3.5mm auxiliary jack
Quality audio from all sources
Outstripped by newer models
No shutdown function or on/off button
LCD display has poor viewing angles
Does not fit well in some cars
The Nulaxy Bluetooth Car FM Transmitter is a very popular transmitter that lets you add Bluetooth audio to an older vehicle through your car radio. The audio quality is sterling and overall the Nulaxy is a solid option, but unfortunately the gooseneck hose didn’t let us position the device in a suitable way inside our test vehicle.
The Nulaxy Bluetooth Car FM Transmitter is one of the most popular FM transmitters on the market. Plug it into a 12V power slot and you can connect almost any Bluetooth-enabled device to your car’s stereo system. We thoroughly tested it to evaluate its design, usability, audio quality, and see if it lives up to its reputation.
The Nulaxy Bluetooth Car FM Transmitter is mounted on a gooseneck for easy positioning. It’s 6.4 x 4.9 x 2.1 inches and weighs in at just 0.8 ounces. The gooseneck is connected to the 12V power plug on one side and the body of the device on the other.
Nulaxy went with a pretty fancy design for a simple device. The large buttons and knob make it easier to use than other transmitters we tested. It comes in six different colors if you want it to better match your car's interior. Overall it’s a nice looking and well-designed device, barring a few issues we encountered during the setup process.
We tested this transmitter in a 2018 Toyota RAV4, which has two 12V auxiliary power outlets under the dash. We found that the Nulaxy Bluetooth FM Transmitter didn’t fit well in either location in our car. In all the promotional photos we saw the transmitter plugged into the center console, closer to the e-brake and shifter. In the RAV4 the 12V power outlets are tucked away under the dash and even with the flexible gooseneck, the transmitter’s body pushed up against the bottom of the dash.
We thought we might be able to solve this problem by positioning the device in a different way, but found that you can’t rotate the body on the gooseneck, and the gooseneck itself isn’t very flexible. At the most we could only adjust it left or right an inch or two, and even then it wouldn’t say in position.
On top of being unable to angle the display up so we could see it better, the display has a very limited viewing angle from the side. Added to the inability to adjust the gooseneck enough, we couldn’t read the display from the driver's seat. From straight on, the display is bright and easy to read, so not being able to properly orient it was unfortunate.
We found that the Nulaxy Bluetooth FM Transmitter didn’t fit well in our car.
Pairing the transmitter with our Bluetooth devices was quick and easy. We adjusted the device and our radio to a clear frequency and heard our music through our car speakers quickly. We were able to answer calls with the press of a button when connected to our phone.
The TF card functionality works well but the device can only play a limited amount of audio file formats, and our library of FLAC music didn’t work. We also plugged our portable music player into the 3.5mm auxiliary jack and everything worked as expected, which is preferable to a MicroSD card anyway.
Besides not being able to get a usable viewing angle, we thought this device was designed well, and in many other vehicles the form factor wouldn’t be an issue. If your 12V power outlets are tucked under the dash like ours, though, you might want to consider other transmitters. We otherwise really liked this Bluetooth FM transmitter, and it’s one of the most popular on the market right now, so it was disappointing it didn’t fit well in the RAV4.
The interference and car ground loop noise with this transmitter is very minimal. Good interference and noise cancellation technology makes a huge difference when you have a mobile device nearby. When audio was playing we didn’t notice anything, though when nothing was playing and our cars volume was up we could hear some buzz and the tiniest bit of cell interference. It wasn’t bothersome, though, and we’ve never encountered a Bluetooth FM transmitter that was completely noise free.
Our go-to for music is usually our FiiO portable music player, so we had to be sure to test the aux input too. We didn’t notice much of a volume difference between Bluetooth and the aux input, but it was just slightly quieter. Unfortunately, the 3.5mm cable that comes with the device was extremely noisy and very low quality. With our own higher quality and better shielded cable, the audio sounded fine, as did the TF card audio which was also around the same volume as the Bluetooth.
Like many newer Bluetooth Car FM Transmitters, the Nulaxy KM18 is equipped with a voltmeter that will display your car battery’s voltage. It’s a nice little feature but is related to what might be a dealbreaker for some—the Nulaxy KM18 has no auto shutoff or on/off button.
With the new generation of Bluetooth FM receivers that are only a little pricier, it’s time for this transmitter to retire.
Nulaxy’s manual states, “To prevent your car battery from being drained, please be sure to remove the KM18 from the car cigarette lighter after use.” We noticed several reports online about car batteries being drained after leaving the adapter plugged in. Some cars continue to provide their 12V power outlets with charge from the battery even when the car is off, which means that if the Nulaxy is still plugged in it will act as a continuous drain. The upgraded KM18 Plus model addresses this problem with an on/off button.
Nulaxy’s transmitter has limited software functionality and the LCD only displays information about your connectivity, music, channel frequency, and car battery charge. Navigating and figuring out how to use the device is easy and the software displays exactly what you need to know, when you need to know it, in a clear way. There are no special features here but we don’t really think any are needed.
The Nulaxy KM18 Bluetooth FM transmitter is in the same price range as most transmitters, but because there’s an upgraded version the KM18 can usually be found for slightly less, around $17 to $20. The newest generation of transmitters are generally in the $20 to $30 price range. Considering some of the features in newer transmitters, we think the extra cost is justified.
You can easily find transmitters with QC3.0 fast charge ports now, and new Bluetooth versions have also been released. While the KM18 features Bluetooth V3.0, transmitters with V4.0+ are now readily available. Our main concern with the Nulaxy KM18 and whether it’s worth the price is the lack of a power button or auto shutoff. If this isn’t a problem for you the Nulaxy is a good product for the price, but we’d still recommend a newer device.
The Sumind BT70B has a different form factor than the Nulaxy, with a wider body that isn’t as tall, meaning it fit better in our vehicle. We still ran into the same problem with the viewing angle and gooseneck as we did with the Nulaxy, however.
The Sumind BT70B otherwise falls into the next generation category of newer Bluetooth FM transmitters. It uses Bluetooth V4.2 and EDR (Enhanced Data Rate), and has both an intelligent 5V/2.4A USB charging port and a QC3.0 fast charge port. At 1.7 inches the LCD backlit display is larger and rotates better on the gooseneck than the Nulaxy. However, the auxiliary port didn’t work as described and we were unable to play music from our portable player. Reports are that it works for some people and not others, so it may be a quality control problem.
Typically priced around $26 to $28, the Sumind is a solid competitor even to the upgraded Nulaxy KM18 Plus. If the auxiliary port problems aren’t a dealbreaker for you, the Sumind is a good buy over this version of the Nulaxy KM18. There are plenty of options out there, though, and form factor is something to pay close attention to before making a purchase.
An older device that’s showing its age.
It has a nice design with adjustable gooseneck, large buttons, and multiple audio source options. It’s also got the lowest levels of noise and interference out of all the devices we tested, sounds great, is easy to use, and looks pretty cool. Unfortunately it suffers from cumbersome design and being outpaced by newer receivers with more features, receivers that are only negligibly more expensive.