Not all Bluetooth audio connections are born equal. The A2DP profile specifies that lossy codecs such as SBC, MP3, AAC and aptX can carry compressed audio data over Bluetooth from transmitter (smartphone, PC) to Bluetooth receiver (DAC, headphones, in-car headset, loudspeakers) with the former automatically selecting the best quality codec according to the receiving device’s technical specifications. That’s the theory.
In practice, it means sound quality heard over a Bluetooth connection is only as good as the weakest link in the chain. The challenge for end users? To ascertain which codec has been auto-selected by the transmitting device, especially in the absence of an aptX-notifying LED.
Bluetooth audio receivers often indicate nothing more than the existence of a connection. And yet knowledge of the type of connection is especially useful to those buying Bluetooth devices on the basis of the (supposedly) superior-sounding aptX code whose developer CSR describes as being ‘CD-like quality’. It isn’t – but with aptX functionality sitting at both ends of the chain, it’s the highest quality Bluetooth audio experience currently available.
With zero mention of any Apple product in CSR’s database of supported hardware, I’d previously deduced that no device running iOS or OS X was aptX-capable. I was only half wrong. Whilst the iPhone and iPad continue to eschew aptX in favour of Apple’s own Bluetooth-compatible codec (AAC), an iMac or Macbook running OS X can in fact transmit aptX-encoded audio to a similarly specified Bluetooth receiver.
Many Apple computers make use of aptX automatically. There’s nothing to do except verify its presence. Here’s how*: I paired a 2014 Macbook Air to a set of Audioengine’s aptX-capable Bluetooth speakers, hit play on a song in VLC and got a Hot Chip remix of New Order bouncing off the walls. I then held down the ‘option’ key, clicked the Bluetooth logo in OS X’s menu bar and moused over the connected device “Audioengine HD”. Et voila! Confirmation of aptX transmission:
Users not seeing aptX, even when playing to an aptX-capable device, can crack OS X into line with Apple’s Bluetooth Explorer tool. Navigate to Tools –> Audio Options and check the box that forces aptX:
Bluetooth Explorer is a free download and ordinarily only available via Apple’s developer channels. Luckily, a little birdy (not Brady) told me that’s it’s also available for download
here. (UPDATE May 2016 – old link expired | UPDATE September 2016: new downlink link here).
PC users are advised that Windows 10 is also fully aptX compatible.
*Thanks to Audioengine USA for the heads up on this.