What actually is hi-res music?

The original master recordings are usually either analogue in which case a higher definition digital version can be made from them or they are digital in which case the masters are normally 24 bit at least. The compression of the 24 bits into a 16 bit CD quality stream is almost always going to have compromises and this is one of the big benefits of genuine high resolution music.  Linn explain all this very well on their music download website.

But it is certainly also true that not all music sold as high resolution is actually anything of the sort. The UK monthly magazine HiFi News reviews some high resolution downloads each month and they include graphs of the spectral content of the music.  This is extremely instructive!

its analogy time.

you know about hi res telly.  More dots on the screen.  Well hi res music isn't like that because you can't hear in bits, you can only hear in analogy.

i started an email exchange with Wally (Gotye) about his last album because he was offering a hi res download and mine had failed to download.This was before his song went global and it was pretty much a DIY thing on his part.  When i complained about my download not working he emailed me and i took the opportunity to ask him about his hi res recording.

Provenance was an issue as you suggest.  Wally was using alot of samples at various sample rates and many were 16 bit.  His own work was recorded in 24 bit but it was mixed with the 16 bit material.  The final product being sold to the punters was a true 24 bit product but only in part and the 16 bit material had to be put into 24 bit package despite the missing bits.  Wally was offering his studio master because that is what the punters wanted but he wasn"t really into the whole 24 bit thing like audiophiles are.  In fact he even had a dig at " audiophiles" obsession with high res in a later radio interview on US radio.  The quality of the content is the first thing, both in terms of the music and the quality of the sonic capture ( microphones etc)

The same issue applies to analogue master tapes.  Sure, the 24 bit 192kHz is the best digital record of the recording, but you can't get something better out of something that is only so so to start with.

That being said, dont forget the photocopy analogy.  Each copy of a copy loses a little.   A better photocopier will lose less. Fewer generations is better as well, particulaly if you are switching between analogue and digital domains.

if you can still find it look for Naim's documentary online about the 24 bit release of  the "Meet me in London" album with Sabine thingy.  In that making of documentary they talk about certain music plugins 

being unavailable at their proposed target data rate.  Than meant they had to come out of the digital domain, manipulate, then back into digital.  Thats a lossy process.

End of the day however a good higher bitrate recording will sound better native than down sampled to 16 bit 44.1. In my experience, and i played with this on a few recordings now.

Or put another way... 

Have you ever compared a CD to vinyl on comparable gear? Notice any difference? Was one better, or just different? 

For me, it's the same with HD audio. I personally haven't heard much HD audio, but what I have heard is just 'different' to what I'm used to. I've been unable to say in all objectivity whether what I've heard has anything ever sounded better, as opposed to being definitely able to see  that a HD broadcast is better than SD, or a hear that a CD is better than a lower bitrate mp3. 

A picture says more than thousand words, and for the rest just allow yourself an A-B test which often is done at a hifi show...

High Res usually refers to 24 bit recordings at 44.1kHz sample rate or above.

When a 24 bit master is reduced to 16bit, what is used is truncation with interpolation and dithering, not compression.  With compression the original dynamic range could be restored by expansion; this cannot be done the last 8 bits of information are lost forever.

It is correct that some unscrupulous suppliers are taking 16 bit audio data repackaging it in a 24bit file and calling it High Res - it's not.  The spectral plot won't detect this however and 24 /44.1 is high res, but still has the same spectral limitations of CD quality.

Bert, that is correct for steady state, but humans can detect time differences to less than a quarter of the period of the signal (using the brain's audio processing to break the Fourier uncertainty limit - see this: phys.org), and this is why higher sample rate can sound better.

The brain can detect timings so fine that an equivalent steady state signal couldn't be heard.

One significant benefit of 24-bit recordings is in the mixing/production options. With  a higher resolution signal, more manipulation (EQ etc) can be done in the digital domain with less effect on the underlying SQ. Once the mastering is complete, relatively little is lost on the final down-sampling to 16-bit.

The dynamic range of 16-bit is more than adequate (and much greater than vinyl offers) if, and here's the kicker, the big if, the mastering uses enough of the available dynamic range. The loudness wars mean that although we have huge dynamic range available on CD format, very many recordings use just a fraction of this. To use the TV analogy, many modern recordings are like video produced with the brightness turned way up. When we display those on our TV, we have to turn the brightness way back down so we can watch it without searing our retinas, but now all the contrast is gone. 

With respect to sampling rate, there is an argument that higher sampling rates mean that the artifacts of filtering are at much higher and extremely inaudible frequencies so less interference with the audible signal. In practice, there isn't much in it especially once you get above 48kHz.

A/B testing isn't too hard. Start with a high res file that you know is high res. Create a downsampled copy and compare them. Comparing a high-res to a CD is in't valid because they are likely to have been mastered differently.

Hi, there is no formal technical definition for hires or high definition in audio as ultimately the term is subjective and relative.. Typically these days however hires or hidef tends to relate to anything that has greater definition, whether in amplitude or frequency spectrum than CD's 44.1/16.

Also it's worth pointing out that you shouldn't fall into the trap of thinking that the sampling rate is merely about filtering and the highest frequencies being reproduced of a 'sound'.. It's also about timing.. That is the timing between sounds.. our ears and brains are very sensitive to this.. And clearly to record digitally this timing, the sample rate has to be at least double the period of the timing interval... fair amount of stuff in the AES (Audio Engineering Society) library on this if you are interested .. Though you need to be a member and/or pay to access as with most professional organisations. Now whether audio equipment, and speakers with room reflections can resolve this effectively is another matter assuming it was recorded in the first place....

Huge,  agree a pic says a thousand words,  but I believe its telling porkies as well.

DSD is generally accepted to have a dynamic range up 120db & extended frequency range in theory up to 100kHz, although in practice most players & recorded media limit at 88kHz 

Respectfully, a bad analogy.  CD and vinyl are so fundamentally different, including but not limited to application of the RIAA equalisation curve, that comparing hi res digital to redbook digital is "nothing" like comparing cd to vinyl. IMHO of course. 

We all know and respect that vinyl is "analog."  But vinyl "sounds like vinyl" for a variety of reasons.  And many of those reasons sit on the continuum from the black disk to the analog input of the pre-amplifier.  There are a lot of "parts" between those two.

NB - this has nothing to do with which is "better"  I have spent many hours of my life listening to both, as have all of us

Huge I agree with what you are saying about 24 bit compared with 16 bit and your explanation is much better than mine, as usual in fact.  But I think you gave misunderstood my point about spectral plots, as per HiFi News reviews.  I wasn't suggesting that these help you identify genuine 24 bit compared with upscale do 16 bit recordings because they plainly can't. But they can help you identify recordings with high sample rates as compared with ups caked lower sample rates and if you pop down to a newsagents and glance at that page or two in the mag, you will see what I am talking about.

best

David

There is a thread " 24-192 a scam" which many finer brains than mine contributed to and may answer some of your questions