Nulaxy KM18 FM Transmitter Reviewed & Tested

If you are looking for a handy way to connect your phone or device to your car’s sound system wirelessly, a Bluetooth FM transmitter could be just what you need. One of the most popular FM transmitters available right now is the KM18 from Nulaxy. In this review we are going to give you our thoughts on the transmitter after using it for a number of months.

How Much Does the Nulaxy KM18 FM Transmitter Cost?

We paid US$18.99 for the KM18 about 12 months ago, which is the same as it is being advertised at the time of writing (on most online stores). This puts it in the mid-range price bracket, with some more expensive and some cheaper options available. We think this is a fair price to pay for the KM18 given its features and specifications.


Bluetooth Version5.0
Product Input 12 – 24V
USB Charger Output 5V/2.1A
Playing Sources Bluetooth/ SD/TF Card/ AUX
Dimensions175 x 49 x 80 mm (6.9 x 1.9 x 3.54 inches)
Screen1.44-inch colour
Frequency Range88.1 to 107.9 MHz
Supported music formatsMP3, WMA, FLAC, and WAV

First Impressions (Packaging, etc,)

The Nulaxy KM18 comes in a nice sturdy box and is very well packaged compared to some of the other transmitters we have tested. We would have preferred to see a little bit less plastic used on the inside, but it isn’t a major issue.

In the box Nulaxy includes the KM18 FM transmitter, AUX cable and some instructions. The transmitter is made from a shiny black plastic material, but other colours are available at a higher price. It is quite lightweight and doesn’t feel as durable as something like the IMDEN C57, but we don’t think this will be a problem.

One thing we didn’t like is the overall size of the transmitter. It is relatively massive compared to some of the other products we have tested and is definitely the biggest FM transmitter we have had our hands on so far. Some won’t have a problem with this, but it definitely sticks out like a sore thumb when plugged into the lighter socket of our cars. This is partly due to its two-part design, with the lighter attachment section being connected to the control section via a flexible gooseneck. This does give you the ability to adjust the screen direction, which can be quite handy when a passenger wants to operate the transmitter.

The one 5V/2.1A charging port sits on the lighter attachment part, while the microSD/TF card slot and AUX input are connected to the control section. There is a large volume knob/multifunction button, a 1.44-inch LCD screen, and controls to change the frequency and songs on the front of the transmitter.


The first step is to plug the KM18 into the lighter socket of your car. This is where we discovered a bit of a problem. In one of our cars we found that the KM18 kept on dropping out/disconnecting from the lighter socket, especially when going over bumps. While this is probably more of an issue with the car itself, no other transmitters we have tested had this issue.

We put it down to a combination of a bad lighter socket and also that the KM18 is quite top heavy. This is obviously a major issue and made the KM18 unusable in this particular car.

The long neck of the KM18 can also be a problem with shifting/selecting a different gear position. On one of our cars we found that it would often get in the way when we put the transmission back into park.

When we did get going, setting up and connecting the transmitter was an easy enough process and is pretty much like any other product we have tested.

Once the KM18 is plugged in the LCD screen will turn on and show the frequency along with a Bluetooth unconnected message. The multifunction/volume knob also blinks to show that the device is not connected.

From here go into the Bluetooth devices list of your phone and find the KM18. Ours popped up immediately, but you may need to give it a second. Select the KM18 transmitter and it should connect. You will know if the connection is successful by looking at the screen. It should say something like Bluetooth KM18 iPhone (replace iPhone with your device’s name).

Following this, adjust the frequency on your car’s radio to a free channel. You should only hear white noise/static. With the frequency set on the radio, do the same on the KM18 transmitter so that they match. This is done via the “CH+” and “CH-“ buttons.

Overall, we found the process to be very easy and pain free. The only issue we discovered is that sometimes it can take a minute or so for the KM18 transmitter to reconnect after restarting the car. This seems to be a fairly common occurrence with a lot of the transmitters we have tested (we have tested with multiple phones/devices).


Instructions are provided in the box and are available online here. The instructions provided in the package come in five different languages; English, French, German, Spanish and Italian.

The instructions give and excellent rundown of all the features and how to use them, from things like answering a call, to activating Siri/Google Assistant, and changing the bass. Overall we were very happy with the instructions.

Sound Quality

The sound quality is pretty good, but don’t think it will be as good as a wired connection. It is slightly muddy and sometimes you can get a bit of static. During back-to-back testing we felt that the sound quality was slightly worse than Nulaxy’s other FM transmitter, the KM30. However, there really is only a slight different and it is probably more down to the fact that you can tune the music slightly on the KM30.

The KM30 also seemed to have slightly less issues with static noise, but in all honesty we only noticed it by going back and forth with each product. If we didn’t do back-to-back testing we don’t think we would have ever noticed a difference.

One issue we did find is that the volume level was reduced quite a bit. This does seem to be an issue with all FM transmitters we have tested, so we can’t really knock it for this. However, it is important to keep this in mind if you like to destroy your hearing (the KM18 gets more than loud enough for us).

The KM18 does have an AUX out, so if you find that you are getting a bit of unwanted noise you can plug the transmitter into your cars AUX input (if it has one). You then continue using Bluetooth to connect your phone/device to the KM18 transmitter. This does improve sound quality, but the cable does look a bit messy.

Playing Music

You can play music via a couple of different methods. The first way is to stream music wirelessly from a device such as a phone. This is what most people will do, but you can play music directly off a microSD card.

To do this, load up some songs to the card and plug it in to the socket on the right of the KM18. Nulaxy states that the microSD card needs to be formatted to FAT32 and must have a capacity of less than 32gb (we didn’t have the chance to test one higher than this).

Once you have plugged the microSD card in, you can play or pause the music by pressing the multifunction button (volume knob). You can then skip a song or go back to the previous one by pressing the forward and back buttons. These controls can also be used if you are playing music from your phone.

Long pressing the forward button will allow you to switch audio sources, while long pressing the back button will switch the music playing mode (repeat all, random, etc.). These two controls only work if you are playing from a microSD card.

We had no problems with the controls and found them easy to use. Being able to control the song playing on the transmitter itself is handy, but we found that we never used the volume knob at all. We just set the volume to the KM18’s volume to maximum and then adjusted the volume via our car’s sound system controls. We did this because we found that if we switched back to the radio it could be quite loud (the KM18 reduces the sound level a bit).


Calling works well on the Nulaxy KM18. If you are receiving a call, simply press the multifunction button once. You can then end the call by doing the same. If you want to reject a call press and hold the multifunction button for two seconds, and if you want to redial the last number press the multifunction button twice. All this works perfectly fine and we had no troubles with it.

The call quality is much the same as what we said in the sound quality section. Once again it is slightly muddy and we came across a bit of static noise, but it wasn’t a problem overall.


The Nulaxy KM18 only comes with one 5V/2.1A charging port. This is a bit disappointing compared to some other transmitters which offer two ports (although one tends to be very slow). However, the KM18 is better than the Avantree CK310 for example that does not offer any charging capabilities.


The KM18 is a good mid-range option, but for a few dollars more we would recommend Nulaxy’s higher tier model, the KM30. It has more features, has ever so slightly better audio quality, and the adjustable neck is far, far better. The KM18’s gooseneck is definitely the worst thing about the device and the fact that the top heaviness causes it to fall out of some lighter sockets and get in the way of shifting is a major issue. If you don’t think that will be a problem there is really nothing wrong with the KM18.

You can read a full comparison of some of the FM transmitters we have tested here.


  • Ben

    From his early days playing the original Gran Turismo and with his Hot Wheels car set, Ben has had a long interest in all things automotive. His first foray into the world of automotive journalism was way back in 2009 and since then he has only grown more interested in the industry. Ben also runs and heads up the video production side of Garage Dreams, focusing on small informative documentaries about some of the world's most legendary cars.

Leave a Comment