Pop quiz, kids: when was the last time you saw a fancy new portable speaker system with an actual, physical smartphone dock? If you have an immediate answer to that question, either you work for the manufacturer that makes said device, or you spend way too much time reading consumer electronics news sites (not that there's anything wrong with that). The fact is, the physical docking connector is going the way of the dodo for anything other than charging and file syncing. If you're playing music from your smartphone or portable media device (or even your laptop computer) to a self-contained media player, home theater, or multi-room music system, chances are good that you're either streaming it wirelessly or wish you could.

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But how? As with most emerging technological trends, there isn't one universally agreed-upon wireless audio streaming standard. Depending on your portable media source, you may even have a choice of several different methods for moving your music from Point A to Point B through the ether, and not all of them are created equally. Let's look at the salient points for the most common wireless streaming audio technologies, starting with the most ubiquitous.

Bluetooth
Bluetooth isn't merely the most common wireless technology used for audio streaming, it's also the simplest - at least in terms of setup and operation. To stream audio from your portable player to a Bluetooth speaker or receiver, you merely need to pair the two devices (a fairly simple and secure process these days that may require you to enter a four-digit password) and press play on your smartphone or other media player. The signal is beamed directly from source to destination, without the assistance of any form of router or other intermediary.

You'd never know it was so simple from looking at the specs list for the average Bluetooth-capable device, though, which is likely to include a mouthful like "Bluetooth v2.1+EDR, Class 2 with SPP, DUN, FAX, LAP, OPP, FTP, HID, HCRP, PAN, BIP, HSP, HFP, A2DP & AVRCP profiles and aptX and AAC codec support" somewhere amongst the rundown of supported formats. Don't freak out. You don't actually need to know what most of those letters and numbers mean. The Class of the device is of interest because it defines the range - in other words, how far your Bluetooth transmitter can be from your Bluetooth receiver. Class 1 devices can have a range up to 100 meters (usually more like 20 or 30); Class 2 devices have a maximum potential range of 30 meters (usually more like five or 10). The reason for all of that other tacked-on jargon is that Bluetooth was originally designed as a short-range personal network - a wireless replacement for RS-232 cables. Enhancements have been added to the technology since its creation to allow it to serve other functions: Human Interface Device Profile (HID), for example, facilitates things like wireless mice, keyboards, and video game controllers, whereas Headset Profile (HSP) provides support for the wireless headsets used with mobile phones. For our purposes, though, the important alphanumerics to focus on are A2DP and aptX.

A2DP (Advanced Audio Distribution Profile) is, simply put, a one-way wireless stereo pipeline between a transmitter (your smartphone, tablet, media player, laptop, etc.) and receiver (your wireless speaker system, AV receiver, dongle, etc.). If your portable device plays music and features Bluetooth, it almost certainly supports A2DP. If a device is marketed as a Bluetooth speaker or Bluetooth add-on for an AVR or other music system, it almost certainly supports A2DP, so you can assume they'll make music together. Beautiful music, though? Maybe. Maybe not. A2DP doesn't deliver a very roomy pipeline for music, which means that the music on your portable media player or smartphone (or computer) probably needs to be compressed before being delivered through the airwaves. By default, A2DP relies on Low Complexity Subband Coding (SBC) to squish the signal, but it can also use other codecs (coder-decoders or compressor-decompressors) to get the job done. One of these is AAC, the codec of choice for iTunes music downloads.

The codec preferred by most Bluetooth streaming aficionados these days is aptX, which purports to deliver near-CD-quality streaming. Not all Bluetooth receivers and speakers support aptX, but many do, as do a number of Bluetooth headphones. Not all media players support it, either. Notably, most HTC and Samsung phones do, but the iPhone doesn't, which brings us to...

AirPlay
Originally called AirTunes back in the days when it merely supported audio, Apple's proprietary content distribution protocol is the music streaming method familiar to most iOS users. AirPlay is in some ways simpler than Bluetooth and in some ways more complex. In its most typical implementation, an AirPlay-capable speaker, AV receiver, Apple TV, or add-on receiver (which can be anything from a dongle to a full-blown Apple AirPort Express is connected to your home network, either via Ethernet or WiFi. Music is streamed via that network from your portable iOS device or directly from iTunes on your computer. In other words, to get music from Point A to Point B via AirPlay, it has to travel through your router (unless you're using AirPlay Direct on an ad hoc network but, my goodness, this article is already getting complicated enough, so let's pretend I didn't type that). That's true whether you're streaming tunes via apps like Spotify or Pandora or streaming the music stored on your iPhone, iPad, or laptop/desktop. My favorite way of employing AirPlay is to use the Remote app on my iPhone or iPad to send files directly from the iTunes library on my computer to the Wireless Music Bridge connected to my Control4 system, but tracing out the networking signals involved there can get a little silly. Any way you go about it, with all involved devices connected to your home network, you simply press the AirPlay button on the source device, select the destination, and you're done. In many cases, AirPlay is built into IP-controllable devices that will power themselves on as soon as they sense an AirPlay signal is headed their way. It's the ultimate in laziness.

Of course, given that it relies on WiFi for wireless streaming, nailing down the range of AirPlay isn't quite as simple as it is with Bluetooth. It really depends on the quality of your network. Assessing its quality is a little easier, though, since AirPlay uses the Apple Lossless codec exc
lusively, which means that anything up to CD-quality files will be delivered with no lossy compression. Anything better than CD quality will get downsampled to 44.1 kHz.

Of course, using AirPlay also means you're locked into the Apple ecosystem, which has a couple of implications. First, you should probably forget about downloading and streaming FLAC files. I'm not saying it can't be done; I'm merely saying that, if you've read this far into a wireless audio streaming primer, you probably shouldn't try. Secondly, if you go hog-wild buying AirPlay-compatible receivers, speakers, and so forth and then decide to switch to Android down the road, you're stuck with a lot of arguably useless gear. That's just the nature of proprietary systems, and that may be one of the reasons why many manufacturers are gravitating away from AirPlay support. There are similar open-architecture alternatives, though, such as ...

Click on over to learn about DLNA, Sonos, and the rest . . .

DLNA
Think of DLNA as "AirPlay for devices that aren't made by Apple." Like AirPlay, DLNA relies on your home network for streaming and, as such, it is just as difficult to pin down in terms of range. It's totally dependent on the quality of your network. DLNA is supported by pretty much every major non-Apple smartphone, including Android devices, Nokia Windows phones, and Blackberry 10. And yes, there are even DLNA apps for iOS - some of them are built-in control apps for AV receivers (the Onkyo Remote iOS app is a notable example), and some of them are dedicated servers that allow you to stream music from your iOS device library to DLNA-compatible players via your home network.

As for the availability of DLNA-capable players, there are a lot of them. Literally millions. There are even DLNA-certified refrigerators, for goodness' sake. But that brings up an interesting point. Just as not all Bluetooth devices are designed for music streaming, not all DLNA-capable devices are designed for music playback. I wasn't kidding about that DLNA-capable refrigerator, but try to stream music to it and nothing will happen. It relies on DLNA for photo sharing only.

The upside is that, given the rather open architecture of DLNA, you're much more likely to be able to stream FLAC and other high-resolution file formats. That ability, of course, depends on the player itself and whether it supports such files. The Pioneer Elite SC-79 networked AV receiver, for example, will accept streaming FLAC files. The Sony PlayStation 3 - which for quite some time was one of the most popular DLNA players - won't, at least not without some serious tinkering.

DLNA can also be a bit fussy overall, despite the fact that it's based on Universal Plug and Play, which is again probably a result of its open architecture. Servers can crash. Setup can be difficult (or it can be a snap, depending on the app). Things have, of course, gotten a lot more streamlined as DLNA has matured, and the interfaces have gotten a lot prettier. But DLNA still has a bit of a reputation as a tinkerer's streaming audio system. If you're looking for something a bit easier, there's always...

Sonos
Sonos hit the scene in 2005 and positively revolutionized the multi-room distributed audio market. Before that, listening to the same source of music in multiple rooms in the house generally meant relying on incredibly expensive audio matrix switchers and miles of wiring buried in the walls or ceilings, more often than not operated by advanced control systems costing tens of thousands of dollars.

Relying on a mix of WiFi and its own proprietary network technology - called SonosNet - the original Sonos system consisted of ZonePlayers, which formed their own mesh network (in other words, the more players you added, the stronger the network became), to which you either connected a set of bookshelf speakers or ran a line-level audio or optical digital output to your home sound system like any other source device. From there, you used a dedicated controller to select music from your computer and streamed it anywhere in the house. Since then, Sonos has introduced numerous new players, some with built-in speakers, as well as a soundbar that can be paired with Sonos players to form a completely wireless surround sound system. Numerous Internet music services have been added, as well, including Pandora, Spotify, MOG, and iheartradio. These days you can even stream music directly from iOS or Android devices.

Setup is also incredibly simple - so simple, in fact, that it either works or it doesn't. I've set up a couple of Sonos systems in my day and, with some computers, it was a matter of plugging it in and patting myself on the back for a job well done. During my Windows 7 days, though, I couldn't get a Sonos system to access my music library to save my furry Wookiee butt.

For being a proprietary system, Sonos does support a wide range of audio file formats, including MP3, WMA, AAC (although not DRM-protected iTunes downloads, if you still have any of those), OGG, both FLAC and ALAC (up to CD quality), AIFF and WAV (with limited metadata support), and even Audible audio book downloads.

And the Rest...
Of course, this isn't an exhaustive list of every streaming audio option out there. There are other proprietary formats, each with its own pluses and minuses - like Kleer, an audiophile alternative to Bluetooth that operates in much the same way, except that it has vastly more bandwidth, requires a transmitter dongle attached to either your portable media player or laptop, and has only ever seen much hardware support from Arcam and Sennheiser. But if you're just dipping your toes into the streaming audio waters, chances are good that one of the above will suit your needs. Which is the best? Again, that depends on what sort of hardware you already own, what sorts of files you want to stream, and how willing you are to find out just how deep the rabbit hole goes.

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