Disclaimer: I didn’t include high-end DAPs such as the AK380/240 because whilst borrowing them, I didn’t conceive of this simple metric. But you can be sure that they, too, would suffer the same fate as the superbly performing MS-AK100 and AK Jr.
Finally, while I didn't write it to be click bait, I suspect that this article, like my Fujifilm GX680III article, is.
Clarification: This article has been updated for grammar, spelling, and to shoehorn the occasional external missing link.
Prior to reading this article, please check out Lachlan’s critique of 24-bit audio, in which he distills the important bits about 24-bits. Whether or not you read this article, and especially if cool-aid isn’t your thing, watch his video.
If you’re a metaphysicist, no amount of evidence will convince you of anything. You probably also believe that stair steps represent discrete sampled signals. This Xiph video may help disabuse of that belief. If it does not, remember: your god or spirit guide, or whatever, tells you to forgive.
Let’s get going
Beyond theoretical benchmarks and personal anecdotes, there is no evidence that hi-res 24-bit audio delivers any audible benefit to the ear, especially at human-safe listening volumes. And as a semi-objective reviewer, I call out audio gear that fails to perform up to its hi-res marketing promises. The latest device to fail is the Sony NW-ZX2. Complete and utter tripe.
Now, if listening to 24-bit audio makes you feel better, or if a particular 24-bit re-master is verifiably better mastered than its 16-bit analogue, have at it. Express to the world how much you appreciate hi-res audio. After all, music should be enjoyed.
But blanket claims that 24-bit audio is better than 16-bit audio are useless without first defining what you mean by better. Internet fora the world round brim with bold claims, praise, and stupefyingly misleading recommendations punctuated by the insincere axiom: sorry about your wallet.
For my part, I am sorry. I have failed to consistently remind Headfonia, ohm, and Head-fi readers of mine that on paper, 24-bit audio delivers incredible performance. But in actual use, 24-bit music is restricted by too many external variables to be of much, if any, non-marketing or post-recording use.
Again, if you have doubts, watch Lachlan’s and Xiph’s videos.
Then, consider your listening habits. Do you listen to music at low or high volumes? Where do you listen to it, in quiet, or loud environments? And, because duds do exist (Sony NW-ZX2), through what equipment do you listen?
I’m an IEM guy: Ultrasone IQ, Grado GR10, Noble K10, MH335DW, and the like, might be in my ears when I’m about town. When Tokyo finally cools to end-of-summer Canadian temperatures (around November) I might even sneak out with a portable headphone on. I really like the Oppo PM-3 and the Audio Technica ES10. No matter the headphone, I listen at safe volumes. I’m a music lover. I want to keep my ears intact.
The main theoretical advantages 24-bit audio has above 16-bit audio are dynamic range, noise, stereo separation, and distortion. Typically, each of these is measured in decibels.
Files with higher bit depth may possess higher dynamic ranges (this is completely dependent on how and where the original instruments were recorded). Theoretically, a 44kHz 16-bit audio file will possess a dynamic range of 96dB; and a 44kHz 24-bit audio file possesses a dynamic range of 133dB. In order for a signal to reach that theoretical maximum dynamic range, it must first possess the such dynamic range to begin with. And, in order to fulfil the requirements of 44kHz 16-bit audio, an instrument must output and sustain 96dB above the loudest ambient noise in the recording studio. For 44kHz 24-bit audio, that value rises to 133dB. Of course, it isn’t possible for any instrument to sustain those values above the loudest ambient noise level. And then there is the noise introduced by the recording and mastering equipment, your playback equipment, and your listening environment. Even in a world devoid of ancillary noise and other errors, in order to truly experience 16-bit audio, your music would have to output a constant volume level of 96dB, a volume at which the government of Canada would limit your daily maximum exposure to 2 hours, and at which, regular, sustained exposure is thought to cause hearing loss.
Dyed-in-the-wool 24-bit audio supporters would have to listen to sustained volume levels of theoretically perfect recordings at 96dB to notice any difference to red-book 16-bit, or 120dB to notice a difference against the theoretical limits of 16-bit dynamic range. And, at those levels, you would lose your hearing in short order. You probably already have a certain amount of hearing loss. But even if you don’t, 24-bit audio carries no advantages.
Loudness theory as it relates to dynamic range is best discussed elsewhere. For my purposes, I wanted to provide a preamble to some descriptive RMAA results I recorded some months ago.
RMAA is useful in illustrating qualitatively objective differences in output from device to device, measured in decibels, against theoretical limits of sampling rates and bit depths. It won’t tell you how a device sounds, or even if you will like it. It will show how well a device conforms to theoretical limits of an audio file.
For the following RMAA results, I matched the volumes of the below devices to a volume at which I am comfortable listening to Aphex Twin’s Selected Ambient Works 85-92 (a particularly quiet album) through an iPhone 4s and Audio Technica ES7 headphone. Naturally, I had to bump that volume up more than I would something from A State of Trance. That volume was seven steps from maximum. Getting both the iPhone 6 and the MS-AK100 to match that exact volume was tough. At seven steps from the top, the iPhone 6’s output is louder than the 4s by several decibels. I spent several minutes scrobbling the volume slider to nail it. The MS-AK100’s analogue-esque step-less volume attenuator was even tougher.
Note: each device was volume matched and recorded without load.
As you can see, at normal listening volumes, no device gains a definite upper hand in any metric. And not a one comes close to outputting signal worthy of 16-bit audio. And unlike recorded music, RMAA tests the theoretical limits of the sampling frequency and bit depth in which was recorded.
In other words, at comfortable listening levels, my 24-bit audio file (TARGET 24-44) has dropped to far below the theoretical dynamic range limits of 16-bit. Even were I Chase Emory, and this were a perfect world where music was recorded in vacuum by exemplary noiseless hardware and whose instruments fulfilled the loudness requirements of 24-bit dynamic range, I could only enjoy the benefits of 24-bit until my hearing was damaged beyond the level at which I could distinguish those differences.
And it isn’t. 24-bit audio is a wonderful marketing tool with theoretical limits that push the development of better and better playback and recording equipment. But it offers no benefits that a comfy belief in the afterlife doesn’t.
Which is fine. If you’re into faith healing, fire walking, finding yourself through magic, or if you gravitate to charismatic leaders and parlour tricks, there’s a cult for you. Your brain is wired to believe nonsense. It is part of our evolution. But willing patterns of self-deception are problematic and dangerous. To the point: your favourite 24-bit music is neither a record of the theoretical limits of the format, nor is it generally listened to at volumes which demonstrate those limits.
Finally, hi-end players playing 24-bit audio at comfortable listening levels offer no demonstrable benefit to a smartphone.