Bluetooth AUX Adapter vs FM Transmitter

If you have an older car audio system that lacks Bluetooth, you can use either a Bluetooth AUX adapter or an FM transmitter to make your car Bluetooth ready. These products can also be used to make your home stereo system Bluetooth compatible.

A Bluetooth AUX adapter or an FM transmitter is very useful if your audio system is non-Bluetooth since they work well in a car audio system, speaker, wired headphones, and home stereo.

In this post we look at the differences between the two products and the pros and cons of each. This will help determine which device would work best for your listening needs.

Table of Contents

What is a Bluetooth AUX Adapter?

A Bluetooth AUX Adapter connects to a cell phone using Bluetooth technology. Audio is transmitted between the phone and the adapter. The adapter is connected to the car stereo through the AUX port.

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What is a Bluetooth FM Transmitter?

A Bluetooth FM transmitter connects to a phone directly and transfers audio using FM frequency band (88-108 MHz). Since every car has an FM Radio it receives this audio signal and plays it.

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The FM transmitter in the picture above has three sources:

  • A Bluetooth connection with a phone
  • Aux out from the phone
  • TF Card

How does a Bluetooth AUX Adapter work?

The Bluetooth Aux adapter plugs into the Aux connector on the car dashboard. This gives it a wired connection to your car’s audio system. The same port can be used to connect to a home stereo system, wired headphones or an amplifier.

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Bluetooth Aux Adapter

A Bluetooth enabled device can stream to the Aux adapter. This can be either a phone, a tablet, a laptop or an MP3 player.

How does a Bluetooth FM Transmitter Work?

An FM transmitter will stream music from other device it connects to directly. This can be any media player like a phone or a tablet.

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The transmitter broadcasts the audio over an FM band of your choosing. The car radio can be used to tune to the same FM band (it functions like a receiver).

Bluetooth AUX Pros and Cons


  • The Bluetooth AUX adapter has in-built noise reduction technology, which makes it an excellent add-in for answering calls via the receiver while driving
  • It has a long-lasting battery which runs for about 16 hours on a two charge
  • The Bluetooth AUX adapter can pair two different devices
  • It is easy to set up and is simple to use. All you have to do is connect the device to the aux port and the USB charging port and start playing away
  • Produces robust sound and ultra-clear quality audio courtesy of the two 2-watts speakers and the adapter’s sound revitalization technology
  • It provides high-fidelity stereo transmission and has noise reduction technology
  • It automatically syncs to already paired devices
  • It has a glowing LED light on the USB, which helps to identify whether the connection is working correctly or not


  • It has limited functionality
  • Some users may find its loud sound irritating
  • It has an annoying hissing sound that plays in the background when the device is idle
  • Subpar quality of calls since the microphone doesn’t work as well as advertised
  • The receiver can make hands-free calls, but their quality decreases over time
  • The device is not very durable and may serve a user for a limited time
  • Siri/Google only through a third-party device.

FM transmitter Pros and Cons


  • The FM transmitter has a great display
  • It produces good sound quality with an advanced noise reduction feature
  • It supports multiple streaming options
  • They come with a 1 Year Warranty after purchase
  • It has an excellent buttons setup for navigation
  • The design is compact and straightforward, which makes it user friendly
  • It has a fast-charging option, and its battery fills up quickly
  • It gives an excellent calling experience when synced to a phone
  • Hands-free calling
  • The FM transmitter also has Siri/Google now capabilities built-in


  • Susceptible to RF interference from FM broadcast stations
  • It doesn’t do well with devices that have weak Bluetooth connectivity
  • It doesn’t display caller ID on its screen
  • The sound provided by FM transmitters is not so great in Bluetooth mode
  • The transmitter has no power off button
  • It produces noise in some car types
  • The transmitter occasionally gets stuck in the target socket
  • FM transmitters lack extra features

Frequently Asked Questions

What is the difference between a FM transmitter and a Bluetooth transmitter?

FM transmitter will send audio signals over the FM band which is 88-108 MHz. Any FM receiver such as a car radio can receive these signals and play them over the speakers. FM transmitters are designed for cars and larger, higher power transmitters are used for parking lots and drive-in movies.

A Bluetooth transmitter will transmit a digital signal over the frequency band 2400-2500 MHz, also simply called 2.4 GHz.

The Bluetooth protocol is a more complicated than FM signals. It’s a digital data signal with the ability to avoid interference through frequency hopping and more.

It’s often the case that FM transmitters and receivers are built as separate devices. A car radio has a receiver but no transmitter. The FM transmitters mentioned in this post cannot receive signals. Bluetooth transmitters and receivers are always built into the same device.

What is the difference between a Bluetooth Transmitter and a Bluetooth Receiver?

A Bluetooth transmitter as the name suggests transmits signals using the Bluetooth protocol. A receiver on the other hand is capable of receiving this signal and turning it into meaningful information. This can be an audio or video stream or simply data that can be used by the receiving device.

Bluetooth AUX or FM Transmitter – which device is better?

When you compare the Bluetooth Aux adapter and FM transmitter, the AUX is better than the FM transmitter because of the following;

  • AUX is easier to use due to its plug and play design
  • The Bluetooth AUX adapter provides a more reliable connection than using an FM transmitter; with a Bluetooth AUX adapter, you can enjoy a better, more dependable connection without the challenge of attempting to broadcast the device signal to available stereos via blank radio frequencies.
  • AUX inputs and devices usually have a better sound quality, and the Bluetooth AUX adapter is no exception. How good the sound quality you enjoy will ultimately be determined by your car stereo’s abilities, though a direct input into the stereo – as opposed to radio – tends to carry superior sound quality.

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