Bluetooth vs AUX vs USB: What's the Best Way To Stream Audio to your BMW?

You're a reasonable, 21st century person. Chances are that means you access most of your music collection through your smartphone, either to play the mp3s you've downloaded or to stream straight from Tidal, Spotify, Apple Music or one of those other ones nobody really uses.

But how do you go about bringing all that mobile musical joy into the most joyously mobile thing you have, your BMW?

The short answer is to connect your smartphone to your BMW, and play your music through the car's stereo speakers. With so many wired and wireless connection options to choose from, though, each with their own advantages and disadvantages, the short answer probably isn't going to be much use. So what exactly do you have a choice between, and why would you go for one connection method over another?

Wireless audio connections

As any audiophile will tell you, wireless audio connections are going to lag behind their wired counterparts when it comes to audio quality. But what they give up in fidelity, they more than make up for in convenience, making them a great choice for people who aren't so concerned about hearing every detail of Jack Ashford's tambourine work.

Bluetooth

Bluetooth is probably the best-known technology used for wireless audio connection, popping up in speakers, headphones and basically any remotely decent phone built in the last decade or so. So it's well established, and you're not going to have a problem finding products to fit into your Bluetooth-based audio ecosystem. BMW knows that, which is why it offers both a basic and Enhanced Bluetooth upgrade for BMWs.

What makes Bluetooth such a firm favorite is how quick and easy it is to pair up two devices and start streaming audio between them. Anybody who's used a wireless earpiece or set of Bluetooth headphones will know that, after the initial setup, it's enough to bring the two devices within range of each other to establish a connection. That means that getting music from your phone playing through your BMW's speakers is as close to automatic as you're going to be able to get.

Bluetooth isn't just for audio, though; the technology was originally designed as a wireless replacement for the old RS-232 serial port, used for connecting mice, printers and other peripherals to computers in the dark days before USB. That means that you can use the Bluetooth connection between your smartphone and BMW to communicate between the two in more advanced ways than just streaming music. With BMW's ConnectedDrive app, you'll also be able to control music playback from mobile apps like Spotify and Pandora through the iDrive, as well as accessing your phone's calendar, emails and text messages through your BMW in compatible vehicles.

The weakness, though, is the audio quality. To allow music to be streamed wirelessly in real time with no delay or stutters, the audio signal has to be compressed by your smartphone to minimize the amount of data that has to be transferred, then decompressed by your BMW for playback. The result is like orange juice from concentrate: not bad, but not a patch on freshly squeezed. The aptX codec found in many smartphones and premium audio equipment promises better quality over Bluetooth, but as of yet it isn't available in any BMWs, so you won't be able to take advantage of that.

WiFi-based (including AirPlay, Miracast, Chromecast Audio and Spotify Connect)

More commonly associated with wireless internet connections, WiFi has emerged as an alternative to Bluetooth for wireless audio transfer between devices. Or at least as the foundation, on top of which a number of technologies have been built.

You can split these technologies into two groups. The first -- best represented by Apple's AirPlay and the competing Miracast standard -- streams audio directly between devices, using the WiFi connection between them as a kind of bridge. WiFi is inherently better than Bluetooth at transferring large amounts of data quickly, meaning better quality audio (and even streaming video) can be moved between devices in real time. Neither AirPlay nor Miracast is supported by the BMW iDrive, but retrofitting a wireless mirroring device can let you use your smartphone to stream music, films and more to your BMW's dashboard display.

The second group tries to get around the limitations of real-time wireless audio transfer between devices by simply not doing it. Google's Chromecast Audio and Spotify Connect both stream music straight from the internet, the former from a whole bunch of apps that offer Google Cast support, the latter from (you guessed it) Spotify. The wireless connection between your smartphone and the Chromecast- or Spotify Connect-toting receiver doesn't go any further than sending commands of what songs to stream, when to pause, when to play, when to skip to the next track.

The obvious disadvantage to all this is that -- even if you manage to find a way to connect a Chromecast Audio to your BMW and power it effectively -- you're always reliant on having an internet connection to access content. That isn't a problem at home, where these devices were designed to be used, but in your car it's a bit of a headache, and a long way from the easy, convenient experience wireless audio connections are supposed to promise.

It's also worth remembering that BMW doesn't offer native support for any of these technologies -- even the Spotify option on the iDrive menu doesn't include Connect. That means having to connect a third-party audio receiver to your vehicle through the iDrive's AUX port, which won't be able to offer a huge audio improvement over connecting directly to the iDrive system via Bluetooth. The added functionality of video streaming means AirPlay (for iPhone users) or Miracast (for Android users) might be the way to go, but as a pure audio solution, the greater convenience of Bluetooth and the superior audio quality available with a wired audio connection don't leave much space for considering WiFi options in your BMW.

Wired audio connections

For people with more discerning ears, a wired audio connection is going to give better audio quality, albeit at the expense of some convenience. BMW designed the iDrive with this in mind, giving a few wired audio connection options to choose from.

Analog: AUX

The typical 3.5mm headphone jack is probably the most familiar audio connection around, and can be found almost everywhere (except, to some people's well-documented chagrin, many of the latest smartphones). BMWs are no different, coming with an AUX port for easily connecting smartphones, mp3 players or whatever else you or your passengers may have to hand. And once the device is connected, you'll be able to pass audio from any app to your BMW.

It isn't as automatic as Bluetooth, of course, forcing you to rummage around for the cable before you can start playing anything. It's not as neat, either, assuming you aren't a fan of seeing stray wires draped over your interior. On the other hand, it can be more reliable than Bluetooth, particularly if you and your family have a few different devices; you don't have to worry about the Bluetooth connection dropping out, or your BMW connecting to the wrong person's phone. There's a reassuring simplicity to plugging in a cable and knowing there's a physical connection between your car and mobile device, and being able to connect a one-off passenger's smartphone instantly, without any Bluetooth pairing.

Where AUX really starts to shine, though, is that it doesn't require compression (at the point of transmission, at least; most music you access through your phone will have already been compressed before you get to play it). The analog signal is piped directly through the cable and into your BMW with all its detail intact, guaranteeing decent audio quality. Not audiophile good -- there's a reason even entry-level hifi systems don't use AUX for anything except headphones -- but it's fine for casual listening.

Digital: USB

To really make the most of your BMW's sound system, though, you can't look past USB. Unlike the analog AUX connection, USB allows transferring clean, digital audio, and the wired connection allows higher data transfer than Bluetooth, translating to better, more detailed audio. The convenience and neatness issues of AUX connections still apply, but in return you'll enjoy the best audio quality available from your phone.

Like Bluetooth (and unlike AUX), activating the USB connection in your BMW allows more than just playing music. The USB connection between the iDrive and your mobile device means far more extensive communication between the two is possible. You can even use the iDrive buttons to control audio playback from your phone, as well as accessing song titles, album art, your calendar, texts and emails on the dashboard display in compatible vehicles. A USB connection can also let you play videos stored on your mobile device, something that isn't possible over AUX or Bluetooth. The full list of available features depends on your BMW and the mobile device you're connecting.

That's the main potential downside to using a USB connection -- not everything is guaranteed to work. Firstly, you need to use a smartphone, which means you can't rig up an old mp3 player like you can with an AUX connection, and if your phone doesn't include compatibility for the full range of features BMW offers, you're out of luck.

So what's best?

Like so many things in life, there's no easy answer. Each audio connection technology has its own strengths and weaknesses, meaning it's suited to specific purposes.

Looking for convenience? Quick and easy connection to Bluetooth can't be beat.

Value versatility? AUX lets you plug in seemingly any device and play back whatever audio you want.

Want great audio quality? There's no better audio quality than that you'll get from connecting over USB.