If there’s one thing we’ve learned over the years, it’s that plenty of people will happily sacrifice audio quality for convenience. Take wireless headphones, for instance. Although seldom a match for a good pair of wired headphones, they are mighty handy.
Recently, however, there has been a conscious push-back for quality. The vinyl resurgence has demonstrated as much, to an extent - LPs certainly aren't convenient. And so has the rise of high-resolution audio. So is there a way to enjoy ease of use without sacrificing performance?
The folks at Qualcomm think so, and to that end they have come up with aptX HD, launched at the start of last year, which brings 24-bit hi-res audio to wireless music. In a nutshell, Bluetooth devices such as portable speakers have just got a lot better. Potentially.
But what's so good about aptX HD? How can you hear it? And what devices are compatible? Read on...
What is aptX Bluetooth?
To understand what aptX HD is, we need to discuss what ‘classic’ aptX is. It is an audio-coding algorithm, created in the 1980s, popular with film studios and radio broadcasters. These days, aptX is synonymous with Bluetooth, which you’ll find on plenty of computers, smartphones, AV receivers, and plenty of other consumer electronics products.
What’s the big deal about aptX? Its party trick is the ability to transmit music, full bandwidth, at a ‘CD-like’ 16-bit/44.1kHz. It’s ‘CD-like’ and not ‘CD-quality’ because aptX uses compression, which helps to reduce audio-coding delays and minimise latency issues. Classic aptX has a compression ratio of 4:1 and a data rate of 352kbps.
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What is aptX HD?
Now for aptX HD. This is essentially an updated, beefed-up aptX with the ability to transfer music in a way that allows better sound quality.
It was released in reaction to the increasing popularity of hi-res audio, and supports audio at 24-bit/48kHz. Compression remains at a ratio of 4:1, with a bitrate of 576kbps.
Whether it is a match for a wired hi-res signal remains to be heard, but Qualcomm seems to be happy gunning for ‘better-than-CD’ sound quality.
What do you need in order to hear aptX HD?
The CSR8675 Bluetooth audio system on chip
There are requirements for using aptX HD. First you need the right hardware. Specifically we’re talking about the CSR8675 Bluetooth audio SOC (system on chip).
Not only can it handle end-to-end 24-bit audio, it also provides greater digital-signal processing than its predecessors. Qualcomm promises a lower signal-to-noise ratio through encoding and decoding, and less distortion too, particularly in the 10-20kHz range.
The requirement for a specific chipset means you will get aptX HD only if you have the right devices in the first place: there is no option for a software upgrade later. Nor is there any scope for any sort of audio ‘upscaling’.
The good news, however, is that you don’t need to worry about backwards/future compatibility. AptX HD devices will be compatible with ‘classic’ aptX headphones and speakers.
Which products support aptX HD?
The LG G5 is going big on audio quality, with a modular design that fits an external DAC
aptX HD was announced in January 2016, and will work with Android smartphones, tablets and portable media players.
The only other smartphones to pack aptX HD are the high-end Vertu Constellation Octane and Luna TG-L900S, both of which are quite niche.
When it comes to portable music players, Astell & Kern is the most prominent supporter of aptX HD. The AK380, AK320, AK300, Award-winning AK70 and brand new Kann are all compatible with the codec, as is its XB10 DAC amplifier.
LG's Tone Active+ and Tone Platinum wireless headsets also features the technology, as do Audio Technica's ATH-DSR9BT and ATH-DSR7BT wireless headphones. Beyerdynamic is one of the latest brands to get onboard too, with its Xelento Wireless headphones supporting the codec.
This list should grow as aptX HD becomes more widespread. You can see a full list of compatible products here.