That’s a shame, as we’ve found iPhones to be the best-sounding smartphones around. They consistently outperform rivals smartphones in terms of pure audio quality, and being able to play better-quality recordings would certainly be a bonus in our eyes.
Apple may not have made it official, but we wondered: is there was a way we could turn our iPhone into a hi-res music player? As it happens, there is – but to say Apple doesn’t make it easy is an understatement, and you'll need to buy a compatible DAC.
If you’re determined to get your hi-res music library playing on your iPhone, here’s everything you need to know.
MORE: Apple iPhone X review
What music files can your iPhone play?
Let’s start with what the iPhone can do out of the box. Apple iTunes and Apple Music - the native music players across laptops and iPhones respectively - can play MP3, AAC, ALAC, WAV and AIFF files.
But Apple products don’t natively support FLAC or DSD files.
So how can the iPhone play hi-res music?
The first thing to know is the lack of hi-res playback isn’t to do with hardware - it’s software-related. The iPhones themselves are capable of playing hi-res tunes, but Apple’s own iTunes and Apple Music software don’t allow full playback of these hi-res files.
This means you just need the right software - an alternative music playing app - that will play hi-res files on your iPhone. Simple, right?
Predictably, it’s not that straightforward with Apple. When you’re listening to music on, say, the iPhone 8 Plus via the Lightning connector, you bypass the iPhone’s internal DAC entirely. You’d think this means we’d be able to play hi-res files unobstructed, but even then we hit a snag. If you’re listening to your iPhone using the Lightning connector, or the Lightning-to-3.5mm adapter that comes bundled with new iPhones, the output is limited to 48kHz. Even if the app is playing 192kHz.
This makes things a tad complicated, but the solution here is to connect an external DAC, such as the Cyrus soundKey or Chord Mojo. Not the most elegant solution, but if you want to hear the full original resolution of your hi-res files through your iPhone, using a DAC is the way to go.
So now we know we need two things to play hi-res files on an iPhone: an iOS app that will read and play the files, and a DAC that let you hear the full resolution of the original hi-res file.
In the past few years, dozens of apps have cropped up on the App Store that claim to play hi-res files (and especially the popular FLAC lossless compression format), but we narrow our choices down to those that support a wide variety of formats, read metadata accurately and, ideally, show us what file format and sample rate is playing.
This last bit is crucial, because if the app can’t (or won’t) show you the resolution of the file, how do you know exactly what is being played?
A surefire way to check that your hi-res file is being played through intact is to connect it to a DAC such as the Audioquest DragonFly Black, the Chord Mojo or Chord Hugo 2. Why? Because these DACs usually have ways of indicating what sample rate is being played. Neat and useful.
We split our testing between the latest iPhone 8 Plus and the older iPhone 6S, both updated to the latest iOS 11 update (11.2.6 at the time of writing). As for the hi-res music, we use a mixture of FLAC and WAV files, ranging from 24bit/44.1kHz to 24bit/192kHz, as well as DSD 2.8MHz files.
More after the break
What are the best apps to play hi-res files on your iPhone?
Of the seven iOS apps we put to the test (Onkyo HF Player, Vox: MP3 & FLAC Music Player, TEAC HR Audio Player, Flacbox, Musicloud, FLAC Player+ and VLC for Mobile), two come out on top: Vox and Onkyo.
Vox is our favourite. With its stylish interface, ability to play all popular hi-res formats and excellent metadata support, it’s a lovely app to use. The visuals are appealing, and it’s a breeze to navigate. You can even pull together music from your iPhone’s library, SoundCloud and Spotify Premium account to create new playlists.
Best of all? It’s entirely free to download and use - though there is a subscription tier if you want to use its unlimited cloud storage and other perks.
Onkyo HF Player is our second choice, mainly because you have to pay an additional £10 to unlock its hi-res ability. This might sound steep, but it’s a one-off payment and the app is reliable, easy to use and has plenty of functions worth paying for. There are various audio and player settings, including upsampling modes, choosing output formats for DSD files, equalisers and more. File support is huge - it can even play quad-DSD - and it keeps your hi-res files separate from the rest of your iPhone music collection.
We particularly like how the app shows both the original sample rate of the audio file and the actual rate being played. It’s what tipped us off about using a DAC to hear the full resolution through an iPhone.
The rest of the apps we tested are either awkward to use, lack metadata support or, in some cases, downsample the hi-res file to CD quality. The TEAC app is one exception. Based on an older version of the Onkyo app (they’re owned by the same company), the TEAC HR Player doesn’t sound quite as good and we prefer the slicker interface of the Onkyo app.
How do I transfer hi-res files to my iPhone?
Now comes the fun part: you've got your new music playing app, and it's time to transfer your hi-res files on to your iPhone. Luckily, this is the easiest bit.
Plug your iPhone into your laptop, fire up iTunes and click on the little iPhone icon that pops up on the top left to see all your phone’s settings and apps. Head to the File Sharing tab (you’ll need to be on the latest iTunes software to see this option) and there, you’ll find a list of apps that allow you to transfer files on to your iPhone.
Select your chosen app, then drag and drop hi-res files from your laptop to the app folder. Press Done, and you’re all set - the files should show up in your iPhone app.
How does hi-res music sound on the iPhone?
Of course, all of this is pointless if there’s no obvious sonic advantage to listening to hi-res music on your iPhone.
We’re happy to report that a hi-res file on Vox is quite clearly a step up in performance - subtler detail, better timing and more expressive dynamics - compared with the same song downloaded in Apple Music (256kbps AAC).
But between the Vox and Onkyo apps? It’s a far closer comparison. We find Vox offers a tad more subtlety and rhythmic punch compared with the Onkyo - it’s just more fun and expressive to listen to.
More importantly, both sound better than Apple’s native Music player.
What kit will I need to listen to hi-res files?
As always, you’ll need the appropriate kit to really get the best out of this arrangement. A good pair of headphones, such as the B&W P5, Sennheiser Momentum 2.0 or Grado SR80e, and a decent DAC (Audioquest DragonFly Red, Cyrus soundKey, Chord Mojo) should be your starting point.
Don’t be afraid to build up to a more revealing system, though: we used the Chord Hugo 2 DAC and Beyerdynamic T1 Generation 2 headphones during our testing, and while that may be a touch overkill and punishingly transparent for an iPhone, don’t forget you’re investing quite a lot in buying hi-res albums. It’s worth it.
You’ll also have to bear with the awkwardness of adding the Lightning-to-USB camera adapter (£29) when plugging in an external DAC to the iPhone, but it’s a small price to pay for finally being able to enjoy hi-res music on your iPhone.