Posted on June 15, 2014
We are starting to see the idea of high resolution audio gain some traction beyond the audiophile world, where it has been enjoyed for the past several years. Some of the major labels, perhaps seeing new opportunities for commerce, have formed a working group to define exactly what high resolution audio is.
I think we're going to see a wide variety of perspectives on this one. The labels are using variations of the term "Master Quality," with different designations, depending on whether the original source is an analog tape, a CD master, or some other digital format. My take is this can be quite vague, particularly in view of the fact that there is such enormous variation from recording to recording, even within one of the above source formats. In some ways, the sonic differences between recordings can far exceed the sonic differences between formats.
Another definition that seems to come up a lot in the hobbyist fora is "anything better than CD quality," meaning anything where the digital audio is encoded with a word length longer than CD's 16-bits and a sample rate higher than CD's 44.1k. (Word length and sample rate are discussed in the previous entry, Is "too much" not enough?)
Sometimes I think terms like "Master Quality" or "CD quality" are oxymorons, like "the sound of silence," "jumbo shrimp," "living dead," or "civil war."
Personally, I would differentiate between "high resolution" and "not as low resolution." How's that for a selling point? "This new album is not as low resolution as the previous one!"
As I hear it, going from 16/44 to 24/44 is an improvement, as is going to 16/48 or 24/48, but I wouldn't refer to any of these as high resolution for the simple reason that to my ears, they are not. 24/44 does not do as much damage to low level information as 16/44 but in my view, it still suffers from an inadequate sampling rate, as does 24/48. The anti-aliasing filter (also discussed in the previous entry) is still way too close to the top of the audible range and its consequences reach down well into the audible range.
As we get to the 2x sample rates (i.e., 88.2k or 96k), there is much less damage and perhaps I'd refer to these as intermediate resolution. I say this because of what I perceive as the critical threshold that is crossed when 4x rates (i.e., 176.4k or 192k) are properly done. These achieve something I've never heard from any other format, including the best analog, and that is what I have been referring to as getting out of the way. This alone makes the 4x rates, to my ears, a bigger jump upward in quality over the 2x rates than the latter are over standard CD. And this alone differentiates them in my mind as being true high resolution.
While the intermediate resolution rates can sound very good, this is exactly what I believe prevents me from thinking of them as high resolution: they sound. I don't want gear or recordings or formats that sound "good," "detailed," "smooth," etc., I want them to not sound. I want them to get out of the way, leaving the sound to that which is being recorded, played, and listened to: the performance.
I'm reminded of how the video world defined intermediate resolutions, those better than standard but not really high, with the term extended.
Personally, I'd place anything at 1x rates (or with a 16-bit word length) in the Standard Resolution Audio category. This would include 16/44, 16/48, 24/44 and 24/48. With the latter two, my experience has been that while the added word length helps, the limitations of having the low-pass filtering so close to the audible range, and thus, its effects within the audible range, mean that in the end these are all effectively just minor variations of CD resolution.
The above is at odds with what appears to be the more common "anything better than CD" definition of high resolution. To me, that is like saying anything better than a Big Mac is filet mignon. Or anything better than Night Train is Dom Perignon. I don't think so. I think there are intermediate levels and that it takes more than being better than mediocre to quality as fine.
Any 2x recording (88.2 kHz or 96 kHz) at 24-bits, I would refer to as Extended Resolution Audio. Now we have a real improvement in fidelity to the input. It doesn't quite get out of the way, but to my ears, it is noticeably better than Standard Resolution Audio.
I would reserve High Resolution Audio for 4x recordings (176.4 kHz or 192 kHz) again, at 24-bits. Properly done and played back on gear that can actually perform at these rates, we have the first format in my experience that is truly capable of getting out of the way. This is what high resolution audio is about.
By these definitions, I would consider Soundkeeper Recordings CDs as well as our CD-Rs* to be Standard Resolution Audio. The latter is certainly closer sounding than the pressing but ultimately, they're both 16-bits. I'd call our 24/96 DVDs* and 24/96 files-on-disc* releases Extended Resolution Audio, and our 24/192 files-on-disc* releases High Resolution Audio.
Of course, as I've long said, my belief is that 90-95% or more of a recording's ultimate sonic quality has already been determined by the time the signals are leaving the microphones. The delivery format just determines how much of that original quality is available for playback. I'd rather hear a CD (or even an mp3) of a Keith Johnson recording than a 24/192 (or the original masters) of recordings from a lot of other engineers. But best of all, is the High Resolution Audio version of Keith's work.
* Editor's note: As of early 2017, when we figured out how to offer downloads without compromising the audio, we started offering these in place of CD-Rs and files-on-disc. Now, in addition to the CD, we offer 16/44, 24/96, and 24/192 downloads in either .aif or .wav format.
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