I've got a music collection of lossy M4A files at assorted bitrates that I want to transfer to my iPhone, and in order to conserve space I want to make each track as small as possible while keeping the quality of it indistinguishable from the original on my computer. I took a small portion of the collection (30 files) and re-encoded each one to two different bitrates to test: 128kbps and 192kbps (what I've been using up till now without any noticeable lack of quality from the originals).

As far as I can make out, the 128kbps files sound exactly the same on my computer as the 192kbps files do, so I'm considering making all of the music on my iPhone 128kbps, but I'm worried about whether these files will sound the same when I transfer them to my iPhone 5.

Is it at all possible that my 128kbps M4A files will play at lower quality on the iPhone? Is the iPhone's playback quality a common bottleneck when it comes to music playback, or will it be able to play 128k files - or any other bitrate, for that matter - the exact same as on my computer? Just wondering whether others have similar experiences on this that could help me make a decision here.


  • Your iPhone has a very capable DAC and supports 16 bit lossless audio which is 1000+kbps. It depends on what kind of headphone/earphone you are using. – Pratik Nov 4 '16 at 8:33
  • too bad Apple doesn't let their users use the state of the art low-bitrate codec (Opus). It can sound good enough even at 64kbps. – Display Name Nov 5 '16 at 13:57

Qualification: I'm a professional sound engineer.

Opinion: By the time you're listening on the move, in the car etc, it's not going to make any difference.

Fact: You can keep your high bit-rate files on the computer & re-encode them on the fly when you sync your iTunes playlists to the phone.
Best of both worlds.

Connect your phone to iTunes, click its icon at the top [not in the sidebar] enter image description here

Select Summary from the sidebar on the left & scroll the main area to the bottom > Options
Select 'Convert higher bit rate songs to... 128kbps AAC'

enter image description here

The first sync after this will be slower, as it does the conversions. After that, you'll not notice the difference.


Lower quality in relation to what? If you listen to high-bitrate music through cheap headphones or earbuds, it won't matter how good the music is reproduced from the iPhone because the limitations of the hardware will 'color' the sound by not reproducing the source material properly through the introduction of distortion, frequency filtering and whatnot. If you are only using your iPhone for casual listening, the higher bit-rate is not necessary.

The proof, for you, is doing some comparisons of your own with identical tracks of various bit-rates on your iPhone, auditioned through the devices you will use to listen, whether it is headphones, earbuds, Bose noise-cancelling devices, car stereos, and what have you.

What sounds good to you is what matters most.

That being said, much earlier models of the iPhone than currently available appear to be excellent music reproduction devices:

Confirming what I hear with critical listening, the iPhone 5 is a wonderful high-fidelity audio source. While publications funded mostly by advertisements from makers of expensive cables, power conditioners and outboard DACs don't want you to know this, the iPhone 5 is a better audio source than most DACs will be when connected to a computer or CD transport. The only difference is that the iPhone has a level 6 dB lower than a proper CD player, but the iPhone still has more output at 1 V full-scale than some outboard audiophile DACs!

  • Thanks for the well-informed answer. To be entirely honest, I was too focused on bottlenecks in the phone itself and elsewhere that I hadn't really considered my earphones as a possible bottleneck at all, I wasn't aware that they really made a difference. I'm using the standard Apple earphones found at amazon.co.uk/Apple-Earphone-Microphone-Remote-iPhone/dp/…. I'm guessing those are pretty low-of-the-range, and hence will be the reason that I won't be able to hear any difference between 128kbps and 192kbps? – Hashim Aziz Nov 8 '16 at 22:23

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