High resolution audio. The science, or lack of...?

[NHL]

One business idea:

Sell CD quality streamed content with label

"Downsampled from DSD",

I would gladly buy!

Environmentally friendly (less storage) and best mastering possible!

 

[Phileas]

If we're a tiny bit sensible and limit the maximum volume to 120 dbs, that gives us a range limit of human hearing of 100 to 120 dbs for people with non-damaged hearing. That's more than 16/44.1 can provide full stop. And it's way more than 16/44.1 can provide without noticeable amounts of distortion.

Clearly there's more to digital audio than The Sampling Theorem (which assumes exact sampling) so there's no point trying to debate that here. The important question is whether you can actually hear the distortion.

It seems to me the best way to determine that would be to insert a Red Book ADA "bottleneck" into an analogue replay chain and compare it with the original in a properly controlled ABX test. I suspect the result would be negative.

 

[andyjm]

If we're a tiny bit sensible and limit the maximum volume to 120 dbs, that gives us a range limit of human hearing of 100 to 120 dbs for people with non-damaged hearing. That's more than 16/44.1 can provide full stop. And it's way more than 16/44.1 can provide without noticeable amounts of distortion.

Clearly there's more to digital audio than The Sampling Theorem (which assumes exact sampling) so there's no point trying to debate that here. The important question is whether you can actually hear the distortion.

It seems to me the best way to determine that would be to insert a Red Book ADA "bottleneck" into an analogue replay chain and compare it with the original in a properly controlled ABX test. I suspect the result would be negative.

Analogue chains have non-infinite signal to noise ratios, limited dynamic range and non linear frequency response. It is wrong to assume that somehow analogue is a no-impact gold standard against which digital sampling needs to be compared.

As I have posted elsewhere, when much younger with better ears, I participated in the re-run of a test at a well known broadcaster to justify the choice of 13 bits for the delivery of stereo programme material to their FM transmitters. The group I was with were unable to tell whether the 13 bit ADA was switched in or out of the replay circuit.

 

[lindsayt]

While your theory is ok, in practice, in a normal listening room, it's irrelevant. I know for a fact that in my house (in a very quiet area) that the noise floor is at 30 to 40 dB when the room is "silent". CD quality is more than enough, and way more than the DR of vinyl.

However I would be quite happy if they upped the standard to 24 bit. It wouldn't hurt and would help with digital volume control issues.

As for Nyquist-Shannon....it has nothing with that to do...44,1 covers any human need...

Frog, thank you for that. So to clarify, would you agree with me that Steve_1979's post about the limits of human hearing and 16/44.1 format was factually incorrect?

I don't understand why he was talking up the CD format to make it appear to be better than it actually is?

 

[Crossie]

The Nyquist Shannon Theorem is of course correct but to implement it properly you need to measure the amplitude using real numbers (real in the mathematical sense ie. infinitely long decimals) since we are using bits (ie. integer values) we will make small errors in our measurements when sampling. This will of course affect the reconversion to an analogue waveform and produce differences from the original input. A higher bit rate will lessen the effect of integer sampling (quantization) and produce a more accurate reconstruction of the original waveform.

Of course whether you can actually hear the difference is an open question.

Crossie

(Retired Chartered Mathematician)

 

[steve_1979]

Frog, thank you for that. So to clarify, would you agree with me that Steve_1979's post about the limits of human hearing and 16/44.1 format was factually incorrect?

I don't understand why he was talking up the CD format to make it appear to be better than it actually is?

My mistake. I should have explained what I ment a bit clearer.

Technically speaking 16/44.1 doesn't go all the way from being as silent as what a young child listening in an anechoic chamber can hear right the way up to being loud enough to making you deaf after a few seconds of listening at maximum volume. But let's be realistic about this and what can actually be used.

What I should have said I'd is that 16/44.1 gives you full dynamic range beyond what anyone would need in any real domestic situation. Unless you are a young child living in an anechoic chamber, 16/44.1 can go from being as quiet as a silent residential room right the way up to ear damaging/borderline painfull volume levels without you needing to touch the volume control. Why would you need anything more than that?

 

[fr0g]

While your theory is ok, in practice, in a normal listening room, it's irrelevant. I know for a fact that in my house (in a very quiet area) that the noise floor is at 30 to 40 dB when the room is "silent". CD quality is more than enough, and way more than the DR of vinyl.

However I would be quite happy if they upped the standard to 24 bit. It wouldn't hurt and would help with digital volume control issues.

As for Nyquist-Shannon....it has nothing with that to do...44,1 covers any human need...

Frog, thank you for that. So to clarify, would you agree with me that Steve_1979's post about the limits of human hearing and 16/44.1 format was factually incorrect?

I don't understand why he was talking up the CD format to make it appear to be better than it actually is?

Yes, I agree that strictly speaking it was incorrect, but in practice, CD quality is comfortably sufficient to cover the human limits of hearing.

Stangely I was buying some music on Linn Records site yesterday and noticed that many of the "studio master" versions were in fact 44.1 KHz but at 24 bit depth...

Picked this one up as it was cheap..the usual premium I feel is far too much (leaping from 11 euros to 21 for the studio master...

http://www.linnrecords.com/recording-just-music-exclusive-linn-compilation.aspx

 

[manicm]

A 44.1kHz sample rate can accurately reproduce any wave upto 22.05kHz and 16bit audio can reproduce the full dynamic range that is audible to humans. What other considerations are necessary?

(A genuine question. Not just being awkward. )

Reading from one of the links that CnoEvil provided the bit depth (16 as you refer to here) has got nothing to do with dynamic range, but the amount of data that can be stored at any interval of time, and which allows for smoother wave form over a given time - hence the potential to sound less sharp or 'digital'. And that is quite understandable to the layman.

This shows a complete misunderstanding of the theorum. NOTHING can sound "digital". It is ALL analogue, and so long as the sample rate is more than half the maximum frequency required, then that analogue wave that comes out of your speakers is identical to what went in...

I wasn't talking about the theorem, I was talking about the bit depth - which you conveniently ignore in your response. In which case it's not a 'complete misunderstanding'.

Manic, I would recommend a bit of googling on the subject as your understanding is definitely adrift here.

Bit depth drives dynamic range.

Sample rate drives maximum frequency that can be correctly sampled.

Yes, and it also gives the listener more information at any given time slice - more bits, more info to hold - hence detail should be increased. If this is agreed upon and technically true I come back to my original question - what the hell is the point of this thread, other than it's been repeated for years and years.

And if one agrees to that then CD was never the 'perfect medium'. Don't worry, I've still been buying CDs like Amazon is being nuked.

 

[oldric_naubhoff]

in general you've got two processes occuring simultaneously when you digitize an analog signal; sampling and quantizing. sampling is based on N-S theorem and it is true that sampling is error-less up to its limit, ie. sampling half band frequency. sampling in analog to digital conversion is responsible for digitazing the frequency spectrum of the signal. however, quantizing is used to capture level of the signal being digitized and quantizing, by definition, will never be error-less, simply because you've only got a limited amount of volume levels which you can apply to analog signal during quantization. as Lindsayt rightly points out; 16 bit resolution gives you 65 536 (or 2^16) discrete levels, 24 bit resolution givvevs you 16 777 216 discrete volume levels, 32 bit resolution nearly 4.3 bilion discrete volume levels. aliasing is a by-product of quantizing process and the reason why it occurs is exactly the fact that you can't fully quantize analog signal.

but on the other hand one might argue that even for 16 bit resolution the number of discrete volume levels is high enough, provided you only use a limited DR within 16bit full DR range, that you could capture the analog signal very faithfully - in effect indistinguishably from the analog input signal. still, the reality is that more bits of resolution are better for the purpose of faithfully capturing of the analog signal.

Quantisation has nothing to do with aliasing,

well spotted Andy. my mistake. change that aliasing to quantization error and all my post stands correct.

Aliasing occurs when an input signal is sampled at less than twice its maximum frequency. Frequencies above (sample rate)/2 appear in the reconstructed signal as lower frequencies or aliases.

The higher frequencies act as if they have been reflected around (sample rate/2). So a 22KHz signal sampled at 40KHz shows up as 18KHz in the reconstructed signal, 30KHz sampled at 40KHz shows up as a10KHz alias. Strange effect, but there it is.

This is a avoided by having an anti aliasing filter before the sampling process to ensure no signal above (sample rate/2) is sampled.

good post there. correct me if I'm wrong but doesn't it mean you'll always have problems with aliasing artifacts since you'd always have input signal with frequencies higher than sample rate/2 (doh). in which case an anti-aliasing filter (regardles digital or analog) is an essencial part of construction of any DAC?

it's not a secret that steep roll off filters induce high amounts of pre and/or post ringing into reconstructed signal. therefore it may be useful to use slow roll-off anti-aliasing filters together with higer sampling frequncies to avoid attenuating of high end of audible frequency range and bleeding of aliasing artifacts into audible frequency range. this is nothing "scientificaly proven" but I red in numerous places that slow roll-off filters "sound" better than fast roll-off ones, which IMO could be plausible since slow roll-off filters induce less digital artifacts into converted signal... this is the only reason I could find that justifies using higher sampling frequencies than standard Red Book.

 

[steve_1979]

Doh! :doh:

I wanted to edit that post and clicked on 'quote' by mistake. Anyway this is the edited paragraph:

"Technically speaking 16/44.1 doesn't have dynamic range that can go upto the limits of human hearing which is all the way from being as silent as what a young child listening in an anechoic chamber can hear right the way up to being loud enough to make you deaf after a few seconds of listening at maximum volume. But let's be realistic about this and what can actually be used."

 

[matt49]

good post there. correct me if I'm wrong but doesn't it mean you'll always have problems with aliasing artifacts since you'd always have input signal with frequencies higher than sample rate/2 (doh). in which case an anti-aliasing filter (regardles digital or analog) is an essencial part of construction of any DAC?

it's not a secret that steep roll off filters induce high amounts of pre and/or post ringing into reconstructed signal. therefore it may be useful to use slow roll-off anti-aliasing filters together with higer sampling frequncies to avoid attenuating of high end of audible frequency range and bleeding of aliasing artifacts into audible frequency range. this is nothing "scientificaly proven" but I red in numerous places that slow roll-off filters "sound" better than fast roll-off ones, which IMO could be plausible since slow roll-off filters induce less digital artifacts into converted signal... this is the only reason I could find that justifies using higher sampling frequencies than standard Red Book.

Yes, this is what I was saying a few pages back, albeit in a bit less less detail.

Glad you've all caught up!

Matt

 

[steve_1979]

... 16/44.1 gives you full dynamic range beyond what anyone would need in any real domestic situation. Unless you are a young child living in an anechoic chamber, 16/44.1 can go from being as quiet as a silent residential room right the way up to ear damaging/borderline painfull volume levels without you needing to touch the volume control. Why would you need anything more than that?

Here's an ironic thought that just struck me. :?

How many of the audiophiles who think that they can hear a difference with 24 bit audio are using underpowered 30-100 watt amplifiers together with power sapping passive speakers? This type of hifi system doesn't even have the necessary dynamic range capabilities to make full use of what 16 bit audio can offer never mind 24 bit.

 

[matt49]

... 16/44.1 gives you full dynamic range beyond what anyone would need in any real domestic situation. Unless you are a young child living in an anechoic chamber, 16/44.1 can go from being as quiet as a silent residential room right the way up to ear damaging/borderline painfull volume levels without you needing to touch the volume control. Why would you need anything more than that?

Here's an ironic thought that just struck me. :?

How many of the audiophiles who think that they can hear a difference with 24 bit audio are using underpowered 30-100 watt amplifiers together with power sapping passive speakers? This type of hifi system doesn't even have the necessary dynamic range capabilities to make full use of what 16 bit audio can offer never mind 24 bit.

This has been an interesting discussion. By banging your "all passive systems are rubbish" drum, you will make it less interesting.

Matt

 

[chebby]

.... underpowered 30-100 watt amplifiers together with power sapping passive speakers?

And there we have the nub of it. The elephant in the room.

(And a little odd from someone using "power sapping passives".)

 

[gtxbla]

Just noticed this thread at a time when I'm considering ditching all of my Cds.

I think the biggest problem is that we don't hear the same. After one of my many Hi Fi upgrades the (then) girlfriend couldn't hear the difference between my existing CD player and my new five-figure purchase - can't say i was best pleased! From that point I didn't care what anyone else heard/thought.

So, regardless of all the technical arguements it's down to the individual to decide what's best. i've gone from vinyl to tape, to CD (including HDCD but not SACD) and now venturing into high resolution audio in the search for 'perfection'. There was a time when the technical/scientific arguments would have counted but not now.

I've managed to get my hands (ears) on some high resolution tracks (Studio Master FLAC 96/24 for those interested). Although I've only played them via headphones from my laptop thus supposedly getting no benefit from the higher resolution, there is a clear difference on some of the tracks. The tracks that I've compared are ones that I thought I knew inside and out no matter what I played them on. This rules out any differences from the hardware and can therefore only be down to the track itself. On one of the tracks in particular there was so much additional detail it was depressing.

I had been about to buy a rather expensive streamer but will most likely go for a DAC. I plan to take one of the CDs and its HR equivalent into my local Hi Fi dealer who will hook them up to compatible equipment so I can finally decide what's best for me.

One of the contibutor's noted that after downgrading he could still hear the same level of detail. I've noticed this but in my view it's because I then know the detail is there because I never noticed it before. I found this often happens when trialling Russ Andrews equipment - the aforementioned search for perfection.

I'm reasonably sure that the HR tracks will be better. How much better and whether it merits replacing its CD equivalent is another matter. I note Fr0g's comment about the 44.1/24 bit CDs from Linn. I simply wouldn't replace a CD with anything less than 96/24. This shouldn't be seen as any criticism of Linn as it's about the only place in the UK you can (legally?) get HR tracks.

 

[manicm]

.... underpowered 30-100 watt amplifiers together with power sapping passive speakers?

How is a really good 100w amplifier underpowered and incapable of making the most of high-res audio? I like how this thread has now turned - from science to lunacy.

 

[daveh75]

(And a little odd from someone using "power sapping passives".)

They're AVI watts though.

 

[steve_1979]

This has been an interesting discussion. By banging your "all passive systems are rubbish" drum, you will make it less interesting.

Matt

I'm not banging any drums and certainly don't think that all passive systems are rubbish. Far from it and the same could be said for any underpowered active systems too. But the fact is that most domestic hifi systems (both active and passive) are underpowered and don't have enough dynamic range capibility to make full use of what 16 bit audio can offer never mind 24 bit.

The ironic thought that I mentioned in my previous post was that many of the audiophiles to think that 24 bit audio is of benefit to them are using underpowered amplifiers (anything under 100 watts give or take) together with passive speakers (which are less efficient than actives) and are only capible of producing a limited amount of dynamic range anyway.

 

[manicm]

The ironic thought that I mentioned in my previous post was that many of the audiophiles to think that 24 bit audio is of benefit to them are using underpowered amplifiers (anything under 100 watts give or take) together with passive speakers (which are less efficient than actives) and are only capible of producing a limited amount of dynamic range anyway.

Please provide a scientific explanation of this, that is easy enough to a layman, that a system with a good 100w amp, or even a good 80w amp, with really good passive speakers is unable to reproduce 24 bit audio adequately. And why will only an active system do so.

Methinks you're skating on very thin scientific ice.

 

[chebby]

http://www.linnrecords.com/recording-just-music-exclusive-linn-compilation.aspx

Thanks.

The link - followed by a little delve around their licensed Decca recordings - reminded me that I don't actually have a Vivaldi 'Four Seasons'. (I used to a long time ago.)

The Linn (Decca, Neville Marriner, Alan Loveday) 16bit/44.1KHz ALAC version is £8 though. (WTF?)

So I have just scored a brand-new/sealed, Penguin Classics CD of the same performance for £2.98 from Amazon. (The version before any tarting around and re-mastering took place.)

 

[steve_1979]

The ironic thought that I mentioned in my previous post was that many of the audiophiles to think that 24 bit audio is of benefit to them are using underpowered amplifiers (anything under 100 watts give or take) together with passive speakers (which are less efficient than actives) and are only capible of producing a limited amount of dynamic range anyway.

Please provide a scientific explanation of this, that is easy enough to a layman, that a system with a good 100w amp, or even a good 80w amp, with really good passive speakers is unable to reproduce 24 bit audio adequately. And why will only an active system do so.

Methinks you're skating on very thin scientific ice.

I never said that only an active system would do. Notice that I said: "the same could be said for any underpowered active systems too".

But to have the dynamic range capibilities to go loud enough to make full use of what 16 bit audio can offer requires an amplifier with plenty of power.

 

[manicm]

I never said that only an active system would do. Notice that I said: "the same could be said for any underpowered active systems too".

Buy to have the dynamic range capibilities to go loud enough to make full use of what 16 bit audio can offer require an amplifier with lots of power.

So, once again, explain why a passive system, with a really good 80w amplifier and quality speakers, is unable to playback high-res audio to a level that is discernible to 16/44, and only a 100w+ system is.

 

[Paul.]

I was learning some things from this thread, please don't make it a passive/active **** measuring thread.

*goes back to lurking*

 

[matt49]

I was learning some things from this thread, please don't make it a passive/active **** measuring thread.

*goes back to lurking*

+1

 

[fr0g]

I never said that only an active system would do. Notice that I said: "the same could be said for any underpowered active systems too".

Buy to have the dynamic range capibilities to go loud enough to make full use of what 16 bit audio can offer require an amplifier with lots of power.

So, once again, explain why a passive system, with a really good 80w amplifier and quality speakers, is unable to playback high-res audio to a level that is discernible to 16/44, and only a 100w+ system is.

The 100 Watts thing is a bit of nonsense from elsewhere...however Steve is correct in saying you will be unable to appreciate a higher DR with a weedy amp.

http://www.crownaudio.com/elect-pwr-req.htm

Put the figures in yourself...

Let's say you have a really well recorded bit of HD music with a 30 dB dynamic range. Your "normal/high" listening level is 85 dB which is loud but not blowing the windows out loud...

If you say you want the middle loudness to be at 85 and allow for peaks of around 100 then you need a 15 dB headroom and preferably a little higher as you risk clipping the occaisional snare hit (or whatever), but we'll stick with 15 for now.

Let's say you have good, sensitive 89 dB at 1m speakers and you are sat 3m away...

In this case you need the amplifier to be able to produce 113 Watts.

You make the speakers some expensive 84 dB efficiency ones and it's over 300.

Of course some good amps that are rated 50, 60 WPC will rise to 100, 200 for peaks, and in those cases you'll be fine...But don't try to use a Nad 3020 for parties...

Saying that, people at parties rarely care about quality, so the occaisional bit of clipping won't matter.

It's all comletely irrelevant though. A 30 dB dynamic range is unusual to the point of almost non-existant. If you used the whole dynamic range of a CD and played at a level where you could hear the lowest levels, the loudest levels would pretty much instantly deafen you.

A quiet room is at around 35 dB. A CD has around 96 dB of DR. So the peaks would be at around 130 dB...Eardrum destroying levels...