If there’s one thing we’ve learned over the years, it’s that plenty of people will happily sacrifice audio quality for convenience. The popularity of music streaming services and wireless headphones are proof of that. Although seldom a match for a well-recorded LP or good pair of wired headphones, they sure 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 telecommunications giant Qualcomm think so. In January 2016, they launched aptX HD - a codec that brings 24-bit hi-res audio to wireless music. In a nutshell, Bluetooth devices such as portable speakers, smartphones and wireless headphones can now sound even 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. It's also designed to sound better than standard Bluetooth. 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. Also called aptX Lossless, it 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 is debatable, and straightforward comparisons are tricky as you can't turn aptX HD on/off on products to discern sound quality differences, but Qualcomm seems to be happy gunning for ‘better-than-CD’ sound quality.
What do you need in order to hear aptX HD?
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?
Android smartphones and tablets were some of the first products to implement aptX HD since its launch, with the LG G5 being the very first smartphone to adopt it. Other LG phones quickly followed - including the latest G7 ThinQ smartphone - and support is now fairly common across various recent smartphones from Sony, OnePlus, Huawei, HTC and Google Pixel.
When it comes to portable music players, Astell & Kern is the most prominent supporter of aptX HD alongside Sony's Walkman. The Award-winning AK70 and Kann, and latest A&norma SR15 and A&ultima SP1000M players are all compatible with the codec.
Beyerdynamic's Xelento Wireless and Aventho headphones support the codec, too, as do the excellent Sony WH-1000XM2 and Award-winning B&W PX noise-cancelling headphones. Audio Technica's ATH-DSR9BT, ATH-DSR7BT and ATH-DSR5BT wireless headphones are also on the list.
Adoption on the hi-fi side has been growing, too: Naim's new Uniti Star, Atom, Nova music systems, Cambridge Audio's Edge A and Edge NQ amplifiers, Dali Callisto speaker system all come with aptX HD built in.
- This list keeps growing as aptX HD becomes more widespread. You can see a full list of compatible products here.
What about aptX Adaptive?
The story doesn't end there: Qualcomm has unleashed the next-generation Bluetooth codec, called aptX Adaptive.
AptX Adaptive will replace aptX HD in time – it essentially combines the current aptX HD and aptX low-latency (which aims to improve the synchronicity of audio and video content) codecs, claiming to improve stability and audio optimisation.
The new codec will take into account the external RF environment around your aptX Adaptive device, so you don't experience any drop-outs when you're taking your phone out of your pocket or bag. It will automatically optimise audio depending if you’re making calls or listening to music, too.
But what's more interesting is that while aptX Adaptive is capable of transmitting 96kHz files wirelessly, even if the codec will launching supporting 48kHz only. That could make hi-res wireless streaming between mobile devices a reality in future, provided the connection is robust enough.
The good news is that aptX Adaptive is backwards compatible with aptX and aptX HD, and with the codec available to headphones and wireless speaker manufacturers from September onwards, we should start seeing it in products in 2019.