Roidmi 3S Review: Is This Car Bluetooth FM Transmitter a Winner?

Bluetooth is everywhere and it’s become the standard for wireless streaming of music. However, many people drive older cars that don’t have Bluetooth built in.

Replacing your car’s headunit with a Bluetooth-enabled car stereo is the best option but that can be pricey. However, the $13 Roidmi 3S aims to solve that problem by streaming your phone’s music via Bluetooth using your car’s FM radio.

Is it worth it? Keep reading my Roidmi 3S review to find out.

Thanks to LightintheBox for sending me a sample to review.

What is the Roidmi 3S?

If you’ve ever wanted to add Bluetooth music streaming to your car without going to the extra cost of a new stereo system, the Roidmi 3S is a fantastic choice.

The $13 Roidmi 3S combines a Bluetooth FM Transmitter and a dual USB charger into a compact unit that plugs directly into your car’s 12V socket (aka cigarette lighter socket).

Just pair up your smartphone to the Roidmi 3S via Bluetooth, download the Roidmi app (Android/iOS), tune your car’s FM radio to the station shown in the app and hit play on your favorite music app to enjoy your music.

It even doubles as a car charger, letting you charge up to two devices at once – an impressive amount of functionality given its budget price tag.

Key Features

  • Stream music to your car’s stereo using Bluetooth
  • Dual USB charger offering up to 3.4A
  • Intuitive smartphone control via the Roidmi Life app

Where to Buy the Roidmi 3S

The Roidmi 3S is available from LightintheBox.

Check Price at LightintheBox

Roidmi 3S Review: Hardware

The Roidmi 3S looks like a standard car USB charger, with the FM transmitter circuitry not adding any extra bulk.

There’s two USB ports on the front of the unit for plugging in your smartphone which supports up to 3.4A across the two ports. Inside the top USB port is a small RGB LED whose color can be configured using the Roidmi app.

Roidmi 3S Review Front

The device fit snugly into my car’s 12V socket and I didn’t have any movement or connection issues.

Roidmi 3S Review: Software

The Roidmi app is polished, like we’ve come to expect from Xiaomi.

Inside the app you can do the following:

  • Set the broadcasting radio station
  • Change the LED color (red/green/cyan/blues)
  • Configure your default music app such as Spotify
  • Set your phone to automatically start music or an app when connected (like Android auto)
  • Update the Roidmi 3S’ firmware

When I first loaded the app, there was already a firmware update available which was automatically downloaded and installed. The whole process was painless.

Roidmi 3S Review: Using It

Using the Roidmi 3S is incredibly simple. Just launch the Roidmi app and plug the device in when your car’s switched on.

The app guides you through the entire setup process, including pairing your smartphone to the Roidmi 3S itself. This made getting everything up and running incredibly simple.

After a brief setup process, just set your car’s FM radio station to the one displayed in the app and you’re ready to go!

Roidmi 3S Review App 01

That said, you might need to adjust the Roidmi’s FM station using the app to find an empty station for the optimal experience otherwise you’ll experience interference.

Getting music playing is as easy as starting your favorite music app (mine’s Spotify) and hit play. It really doesn’t get easier.

You can also route your phonecall’s audio through the car stereo for a much more pleasant handsfree experience. There was a slight delay when answering calls but it was far better to use my car’s speakers than my phone’s speaker.

You can also charge up to two USB devices (to a total of 3.4 amps) so you’ll have enough power to charge two phones at the same time. However, with a 3.4A maximum charging current, only 1 device will charge at full speed.

Roidmi 3S Review: Sound Quality

As the Roidmi 3S uses an FM transmitter, you need to have realistic sound quality expectations. You’re not going to get CD quality here, but most users will be more than happy with the audio quality on offer.

Roidmi 3S Review 02

Sound quality was generally good once I found a free radio station, though I needed to turn up my car’s stereo rather than the phone to avoid distortion that appeared when my phone’s volume was on max.

There’s also a built-in noise reduction feature minimizing any hiss for improved audio but the most important thing is to use a free radio station to get the cleanest possible audio experience.

Should You Buy the Roidmi 3S?

Roidmi 3S Review Side

The Roidmi 3S is a fantastic way to add Bluetooth music to your car for a very small investment. For only $13, you’re getting a solid Bluetooth FM transmitter as well as dual USB charging. This incredibe value makes the Roidmi 3S a must-buy for anyone wanting to add Bluetooth to their car.


  • Intuitive app makes it easy to set up
  • Good audio quality
  • Updatable firmware


  • Some distortion when using maximum phone volume
  • Delay when answering calls

Where to Buy the Roidmi 3S

The Roidmi 3S is available from LightintheBox.

Check Price at LightintheBox
Roidmi 3S Review 01
Roidmi 3S Bluetooth FM transmitter
The Roidmi 3S Bluetooth FM transmitter is an excellent way of adding Bluetooth music streaming to your car. Whilst I wish it had more charging power, it's performance is excellent - particularly when you consider its very wallet-friendly price tag.
Intuitive app makes it easy to set up
Good audio quality
Updatable firmware
Some distortion when using maximum phone volume
Delay when answering calls


Michael is a technology expert with over 15 years of experience in IT, Home Theatre and Automation. Feel free to send Michael a message here.

You May Also Like...


Koogeek Smart Plug Review: Apple Home Automation on a Budget

ROMOSS QS05 Review: Is This Go-Anywhere Powerbank Any Good?


4 thoughts on “Roidmi 3S Review: Is This Car Bluetooth FM Transmitter a Winner?”

  1. Hi Michael. You have written we can route phonecall’s audio through the car stereo using Roidmi 3S. However, I am unable to do so in my Roidmi 3S. The ringing sound is routed via the car sterio but the actual phonecall is not. Is there any special configuration required?
    Also, after upgrading to the latest firmware 16 on Roidmi, i found that the volume of transmission dipped.

    • Hi Obelixx,

      You just need to make sure your phone is routing call audio to the Roidmi (e.g. Samsung phones have a audio output setting) and I seem to recall there’s a setting in the app to let you answer calls on the Roidmi…

    • Hi Pete, I used 99.5 but what I normally do is use my normal radio to scan channels and find something with pure static and then use that :)


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.