High-res audio (HRA) has emerged as arguably the ultimate sonic selection for digital music fans, but what's it all about, what do you need? Allow us to explain.
2015 has seen high-resolution audio (HRA) hit the mainstream, thanks to the release of more devices and services that support the audio format.
From Neil Young's PonoPlayer to high-res audio support on the Sony Xperia Z3 - Z5 and high-res streaming on Qobuz, there's been plenty of noise around HD audio.
But how did it all start and where is the market heading?
As the music industry shifted away from physical media such as CD and vinyl (the vinyl resurgence not withstanding), many of us moved to digital downloads from sites such as Amazon and iTunes, and latterly streaming services, such as Spotify.
These sites use compressed file formats with relatively and low bitrates, such as 256kbps AAC files on iTunes and 320kbps MP3 streams on Spotify.
And with regards to sound quality, these formats aren't telling the full story of our favourite songs. The use of lossy compression means that data is lost in the encoding process, which means resolution is sacrificed for the sake of convenience and smaller file sizes.
This might be fine on the bus when you're listening to your iPod or smartphone, but some serious music fans want better. This is where high-resolution audio – or HRA, the term coined by the Consumer Electronics Association – steps in.
Astell & Kern, LG, Samsung, Sony and FiiO are just some of the companies to have launched high-resolution audio compatible products so far, while several download sites now offer better-than-CD quality music files, with the likes of HDtracks and Qobuz now live in the UK. HRA also has the support of major labels and musicians.
But what does high-resolution audio actually mean? Where can you get it? And what do you need to play it on? Don't worry – all your questions and more are answered on this page.
What is high-resolution audio?
Before we address this, it’s worth pointing out that the definition of high-resolution audio isn’t set in stone. Unlike high-definition video, which has to meet certain criteria to earn the name, there’s no universal standard for high-res audio.
But it tends to refer to audio that has a higher sampling frequency and bit depth than CD, which is 16-bit/44.1kHz. High-resolution audio files usually use a sampling frequency or 96kHz or 192kHz at 24-bit, but you can also have 88.2kHz and 176.4kHz files too.
Sampling frequency means the number of times samples are taken per second when the analogue sound waves are converted into digital. The more bits there are meanwhile, the more accurately the signal can be measured in the first place, so 16-bit to 24-bit can see a noticeable leap in quality.
The Digital Entertainment Group, Consumer Electronics Association and The Recording Academy have, together with record labels, come up with a formal definition for high-res audio.
As well as the definition - "Lossless audio that is capable of reproducing the full range of sound from recordings that have been mastered from better than CD quality music sources" - there are four different recording categories based on the source of the file.
There are several high-resolution audio file formats to choose from, all of which support the above sampling rates and bit-depths. They include FLAC (Free Lossless Audio Codec) and ALAC (Apple Lossless Audio Codec), both of which are compressed but in a way that (in theory) no information is lost.
Other formats include WAV, AIFF and DSD, the format used for Super Audio CDs. The relative merits of the formats can be argued but most crucial will be compatibility with your particular products and system.
FLAC tends to be the most popular, scoring points over WAV for better meta-data support, ensuring your tracks have artist and title information. There's a healthy debate on the What Hi-Fi? Forum on the subject of FLAC vs. WAV.
Of course, as well as downloading your music in these superior formats, and now streaming, you can - and should - also rip your existing music library in these higher-quality file formats.
What’s so good about high-res audio?
Obviously the main claimed benefit of high-resolution audio files is superior sound quality over compressed audio formats.
To illustrate why they should sound better than MP3s, for example, let’s compare the relative bitrates. The highest quality MP3 has a bitrate of 320kbps, whereas a 24-bit/192kHz file is transferred at a rate of 9216kbps. Music CDs are transferred at 1411kbps.
24-bit/96k or 24-bit/192kHz files should therefore more closely replicate the sound quality that the musicians and engineers were working with in the studio.
With more information to play with, high-resolution audio tends to boast greater detail and texture, bringing listeners closer to the original performance.
Though, as always, there are some people that can't hear a difference. As with all the products we review, if you can't see or hear a difference, then save your money...
High-res music on mobile
High-res audio isn’t just confined to the hi-fi market. Several of the latest smartphones play music in sparking 24-bit/192kHz quality, including the LG G3, Sony Xperia Z3 - Z5 and Samsung Galaxy Note 4, while the Onkyo HF Player app allows you to play high-res music on any compatible mobile phone.
The iPhone 6 sadly doesn't support high-res audio out of the box but there is the potential to connect devices via the Lightning output rather than the headphone jack to send a digital audio signal.
The Philips M2L headphones are the first to use the Lightning connection, bypassing the iPhone's internal DAC to instead use their own high-res capable DAC.
And Qobuz has provided a world first for Android mobile users: the ability to stream high-res music on your phone via its streaming service.
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