Aux vs. Bluetooth: What's the Difference?

Which is more convenient, and which delivers better sound?

The key difference between Aux and Bluetooth is that one is wireless and the other is wired.

An Aux (auxiliary) connection refers to any secondary wired connection, but it is most commonly associated with the 3.5mm "headphone" jack. Bluetooth is a wireless technology standard used to connect keyboards, headsets, speakers, controllers, and other peripheral devices to a host computer like a laptop, phone, or tablet.

Apart from the wired vs. wireless distinction, what else separates an Aux connection from a Bluetooth connection? When it comes to convenience, compatibility, and sound quality, which one is better?

Bluetooth vs Aux
 Lifewire 

Overall Findings

Aux
  • Wired—limited to range of 3.5mm cable.

  • Ubiquitous: Aux inputs found on CD players, car head units, portable speakers, record players, home theater receivers, some musical instruments, and most smartphones and tablets.

  • Superior sound quality, though most people won't notice a different.

  • No need to set up, pair, or digitally connect to a speaker or playback device.

Bluetooth
  • Wireless—ranges up to 33 feet in most cases.

  • Only compatible with other Bluetooth devices—not as ubiquitous as Aux but slowly getting there.

  • Not just for sound systems—also connects keyboards, printers, headsets, drawing tablets, and hard drives.

  • Inferior sound quality, but most people won't notice a difference.

  • Requires pairing process, which can be frustrating.

While "Aux" may refer to any auxiliary or secondary input, it is most commonly associated with the common 3.5mm headphone jack, which has been around since the 1950s. They're also sometimes referred to as phone plugs, stereo plugs, headphone jacks, audio jacks, 1/8-Inch cords, or any other iteration of those terms.

Bluetooth, meanwhile, refers to a wireless connectivity standard for computers and their peripheral devices. While not as universal as Aux inputs, Bluetooth is increasingly common.

Convenience: Aux Is Faster, Universal, and Wired

Aux
  • Wired.

  • Easy to set up: No need to "pair" or install a compatible device.

  • Almost every audio-playing device has an Aux input.

Bluetooth
  • Wireless.

  • Ranges up to 33 feet but requires "pairing" process.

  • Not as universal as Aux, but increasingly common.

It's easy and perhaps faster to connect a phone to a speaker system with an aux cable, but the presence of a cord limits the range between a device and its host. There's no need to digitally set up an Aux connection; you only need a headphone jack running from the audio source to an Aux input on a speaker or receiver. Unlike Bluetooth audio, however, Aux connections require a physical cord, which can get lost or damaged.

Because Aux connections are analog, there is a wider range of compatible sound systems. Almost every audio-playing device has an Aux input, including CD players, head units, portable speakers, record players, home theater receivers, some musical instruments, and most smartphones and tablets. (The biggest exception here is every iPhone made since 2016.)

Bluetooth is a wireless standard, which allows for a lot more freedom of movement between a device and its host. Most connections are effective at distances of up to 33 feet. (Some industrial use cases range up to 300 feet or more.)

For car audio, Bluetooth connections allow for hands-free control through virtual assistants like Siri. This also allows you to make hands-free calls, which you cannot do with an Aux connection.

Bluetooth connections can be finicky. In order to connect a phone or media-playing device to a speaker system, you must place the speaker on a "discovery" mode and use your phone to locate the speaker. This process is not always as easy as advertised. If two devices won't pair, you will have to repeat the process until it works. Because software is always being updated, old or outdated devices can be a challenge to connect. Some pairings also require a passcode to complete a connection. All this can make the process of playing audio more of a startup hassle than an Aux cord.

Sound Quality: Aux Delivers Superior Sound Without Data Loss

Aux
  • Lossless analog audio transfer.

  • No compression or conversion of audio to meet wireless standard.

  • Theoretically superior sound but some people may not notice difference.

Bluetooth
  • Compressed audio loses some data to meet wireless standard.

  • Theoretically inferior sound but some people may not notice difference.

Bluetooth audio is generally considered inferior to most wired audio connections, including 3.5mm Aux connections. This is because sending audio via a wireless Bluetooth connection involves compressing digital audio into an analog signal at one end, and then decompressing it into a digital signal on the other. This conversion results in a minor loss of sound fidelity.

While most people will not be able to notice the difference, the process contrasts with aux connections, which are analog from end to end. (Digital-to-analog conversion is performed by the computer or phone hosting the audio.)

Although the sound quality is theoretically superior, Aux does have a few drawbacks. Because it is a physical connection aux cords tend to wear out over time. The repeated plugging and unplugging of the cord can slowly erode the metal, creating poor connections that distort audio. Shorts in the electrical flow can also introduce audible noise. For wired connections, digital USB connections generally provide better sound quality, but, again, not everyone will notice a difference.

On high-end sound systems those differences will become more clear—be it through Aux, Bluetooth, or USB. As such, an Aux connection will always provide higher quality audio than Bluetooth, and a digital connection (like USB) will provide even better sound. The differences in fidelity between each source must be weighed against the differences in convenience.

Old and Ubiquitous vs. New and Versatile

"Aux" describes any secondary audio connection, but most commonly refers to the ubiquitous 3.5mm headphone jack. The technical term for this type of aux connection is TRS, or TRRS, which stand for "Tip, Ring, Sleeve" and "Tip, Ring, Ring, Sleeve," respectively. These names, in turn, refer to the physical metal contacts in the plug head.

It's precisely because Aux cords are time-tested that they remain so common. They are not without their drawbacks, but the simple analog convenience stands for their popularity. That said, Bluetooth is catching up.

The motivation behind Bluetooth was to come up with a faster, wireless alternative to the RS-232 serial port connection for personal computers in the 1990s. The serial port was largely replaced by USB by the end of that decade, but Bluetooth eventually found its way into the mainstream as well.

Since Bluetooth allows for the creation of mostly secure, local, wireless networks, the technology can be used for more than just listening to audio. It's used to connect keyboards, printers, headsets, drawing tablets, and hard drives.

Bluetooth is not a one-to-one stand-in for a 3.5mm headphone jack. Each standard has its core use cases, but as media becomes more and more wireless and digital, the case for Bluetooth becomes more and more compelling.