Yes, wireless speakers and headphones are cheaper and better than ever before. But if you want to retrofit an existing stereo system or old boom box to be wireless compatible, the Logitech Bluetooth Music Receiver is just the ticket. This little box makes anything with an auxiliary line-in -- including any old set of PC speakers -- Bluetooth compatible, so you can stream audio from pretty much any smartphone, tablet or Mac -- any many PCs, too. Best of all it retails for as little as $30 (£30, AU$55).
This model is the second generation of Logitech's popular wireless streaming accessory. The new one is smaller than the first version so it's easy to hide behind a receiver or a speaker, since Bluetooth doesn't need line of sight with the source to operate. Like the original, the device draws power from a wall adapter that plugs into the back.
The rear also has a 3.5mm port and RCA jacks to output audio, and the box includes a 3.5mm-to-RCA cable so you can run it in whichever direction you want depending on the audio source in use. The convenience of this system is its flexibility -- you can hook it up to anything with a free input, including a stereo, AV receiver, TV or PC speakers.
Once you wire the adapter to an input, all you have to do is link it to your Bluetooth-enabled device via the pairing button on top. Press it once to put it in pairing mode, then simply click on the adapter in your device's Bluetooth settings menu to connect. Your speakers should emit an audible jingle to let you know the pairing is successful, and that's it. You can even connect two devices at once so you don't have to keep switching them on and off, but only one source will play audio at a time.
According to Logitech, the range of the Bluetooth connection is 50 feet (15 meters). I was actually able to walk a little farther than that in my apartment without dropping the connection, but your mileage may vary depending on other devices you have in the same room, the thickness of your walls and so forth. But like nearly any Bluetooth device, you'll still get occasional wireless hiccups and dropouts.
That leaves the Chromecast Audio from Google. The Chromecast and the Logitech are about the same price and they accomplish the same goal, turning any stereo with an open auxiliary port into a wireless music system, but with a few key differences in features.
The Chromecast uses Wi-Fi to connect and offers full-resolution 24-bit/96kHz audio resolution playback. You can buy multiple units and add them to several speakers to listen simultaneously in different rooms. It offers universal compatibility on Android devices, but iPhones and iPads are limited to outputting audio from a smaller list of compatible apps. (You can also output audio from the Chrome browser on Mac or Windows.)
In contrast, the Logitech uses Bluetooth for music playback, which compresses audio files to send them over the air. In a nutshell, the music might not sound as dynamic and full as a Chromecast Audio hookup if you're listening through high-quality bookshelf or floor-standing speakers (if you're using TV speakers or PC speakers, you won't notice much difference). On the other hand, the advantage of Bluetooth is that you can output audio from any application on your computer or phone.
For example, I plugged it into my stereo at home and really enjoyed listening to movies and TV shows downloaded locally on my computer using VLC -- I wouldn't be able to do that with a Chromecast.
The decision to buy either the Chromecast or the Logitech Bluetooth adapter comes down to deciding how you'll use them. If the idea of multiroom playback and audio fidelity are a big deal to you, you want the Chromecast.
But if you're just trying to output audio from a single source and don't want to be held back by compatible applications (and don't mind a slight dip in audio quality), the Logitech Bluetooth Music Receiver is your best bet.