Speaking as someone who started out being schooled in the Electrical Engineering arts, I’m somewhat skeptical about the whole thing. As others have noted, the term high definition audio doesn’t specify anything. An an analogue to high definition video, it presumably indicates a digital standard that is to compact discs what the Blu-ray disc is to the DVD. I find that inference to be somewhat ironic since digital music players started out using low bit rate MP3 files that employed lossy compression which produced sound with far inferior fidelity to the 44.1 kHz/16-bit uncompressed audio available on compact discs.
Time and technology have improved the quality of digital audio that can be purchased online or ripped from compact discs at home, but how much is too much? Bigger sampling rates, higher bit resolution, and less compression translate into bigger digital files. The values selected for compact discs were not selected randomly as others have discussed extensively, and to my mind, quite convincingly. The Red Book compact disc spec was not designed to be a compromise when it came to the quality of sound it reproduced.
There will always be those who quibble about the quality of the compact disc standard. Sony and Phillips even went so far as to develop a successor standard, Super Audio CD (SACD) and this case is instructive. The specs of SACDs are in every way superior; frequency range, dynamic range, and capacity are all better than Red Book CD and should exceed the human capacity to hear. Yet, double blind testing by the Audio Engineering Society (AES) shows that SACDs do not sound better than CDs — in tests with about 550 people (many of them professed audiophiles,) slightly less than half correctly identified the SACD. If SACD truly was better, the results would show something substantially better than the 50/50 outcome of a series of random coin flips.
So why bother with new standards like SACD? I believe the biggest gain is in digital mastering. Sony developed Direct Stream Digital (DSD) that substantially simplified and improved the equipment mastering chain for converting music on analog tapes or directly storing data from digital mixing boards. As a next generation format supposedly superior to CD, Sony and other labels also took the time to make sure that SACD releases were re-mastered carefully to DSD instead of rushing crap out into the marketplace as was done with CDs in the 1980s. I’d be curious to know if the sample loops in the AES study were taken from the same DSD master (e.g. different layers in the same hybrid-SACD.) Proper experimental method suggests that they should. A meaningful follow-on would be to compare the DSD version to some previous re-master in double blind tests. My bet is that the mastering is a big part of the thing.
(That said, I own some SACDs. I love the format and the sound. Perhaps it is confirmation bias.)
As for the quality of the hardware itself, Apple sets the standard in the personal digital player domain and I’m going to guess that they would want to set it reasonably high. Steve Jobs was partially deaf, and he could not demand audio perfection completely out of personal experience. Yet he was known for making products into art, and I’m sure he did not want to put the Apple logo on a product that did not meet a fairly acute listening standard given the state of technology at any point and time. Is an iPod/iPhone a true audiophile device? Probably not. I’d guess that it’s good to excellent, but not mind blowing. Better circuitry for a dedicated listening device is a niche something like Pono could fill.
Where the Apple player and its competitors really fail (if you can call it that) is the ear buds or earpods. There is only so much you can do with such a small volume of space. They look cool, sure. Apple also tries hard to create a product with real substance, but an over ear headphone can provide much better sound reproduction. I recently acquired a pair of Grado SR60e headphones, and the improvement in listening experience is significant.
Finally, more and better options for digital data files are a welcome development. A link in the sound reproduction chain that not too many people talk about is the file format and conversion software. The initial popularity of digital music players was fanned by MP3 files — a format whose digital audio output is only an approximation of the input in order to get real size savings (i.e. lossy compression.) Apple devices use AAC files with some some well understood software to create them, which is clearly a step up while still using lossy compression.
A number of audiophiles say that better fidelity and detail requires files that use loss-less compression — the reproduced output is identical to the digital audio input. The price for that fidelity is file size — I recently started using Apple Lossless Audio Compression (ALAC) files for CDs I rip and they take up 8-10 times the amount of disk space. I couldn’t fit my whole CD collection on my current iPod using ALAC files, but I should do some a head-to-head comparison one of these days to investigate what the differences are like.
Given much more economical fixes I can make to my music listening, I’m going to give Pono and its ilk a pass, for now at least.
I recall hearing Neil Young say that “we are living in a sonic dark age” in an interview or at a press conference sometime about 20 years ago. At that time, he extolled the virtues of vinyl and analog sound in an industry that was milking the upgrade to compact disc. I’m glad to see that he now sees that it’s a largely digital landscape. Trying to raise the level of expectation from the listening public is a laudable goal. I’m just not sure that sound engineers would agree that he’s going about it in the best fashion.