General debate thread about audio measurements

[dc655321]

As to limiting the bandwidth of the signal to avoid ringing, that is well known, but in practice, I am not sure how you would do that, as the whole purpose of the filters is to limit the bandwidth of said signals.

For example, I've mentioned the underdamped filters in ESS DAC's, and it's easy to measure transient response. We know as well what underdamping, overdamping, and critical damping sound like, since we've had a lot of experience. So that would have to be measured.

It is statements like these and many others that lead me to believe you are an "engineer" in the same sense that someone who drives a train is an "engineer"...

WTAF?

I wish @Thomas savage were still on duty to nip your nonsense in the bud

 

[March Audio]

That would be true in a perfectly linear system. Neither amplifiers nor loudspeakers nor ears nor the air are perfectly linear and it's well known that the nonlinearity of air alone can make ultrasonic sounds audible.

Personally, I have no opinion on whether the ultrasonic ringing has audible effects, as I'm not aware of any experiments. But I can't rule it out simply because the ringing occurs at inaudible frequencies.

As to limiting the bandwidth of the signal to avoid ringing, that is well known, but in practice, I am not sure how you would do that, as the whole purpose of the filters is to limit the bandwidth of said signals.

No its perfectly true period.

Why do you not have an opinion regarding signals that are above the audible range being inaudible? It's been scientific fact proven by experiment for a very, very long time.

The bandwidth limiting is performed by the anti alias filter in the ADC to comply with the most basic aspects of digital audio recording.

 

[March Audio]

I'm not sure what you're saying here. The quote "Really, if measurements were telling us the full story about DAC's they all would sound pretty much the same, so much of what's in the graphs is below the threshold of hearing!" implies exactly the same thing. So let me try to clarify my point. I'm saying that when I apply what I know of psychoacoustics to Amirm's measurements,not.

You are on really dodgy territory here. I would suggest that you take a detailed look at @amirm background before you start talking about psychoacoustics.

Funnily enough when assessed under controlled conditions dacs that measure very similar do indeed sound very similar. Your earlier assertion that DAC's sound "dramatically" different doesn't hold any water. It does however inform me how innacurate and misjudged your subjective opinions are, for whatever reason. You need to come up with some scientific evidence to support your claim there. Good luck with that.

In the mean time I am putting you on ignore because this is otherwise just baseless and clichéd audiophile waffling. It's not what this forum is about and a massive waste of time engaging.

 

[josh358]

@josh358: I see a lot of claims in your last few posts, but no references to studies (e.g. properly conducted double-blind tests) to back them up. You might have more success convincing people here if you could provide some.

I'm not sure what you want me to refer to. I've assumed that most here are familiar with major studies on the statistical validity of ABX testing, the weighted audibility of distortion components, the Harman research on the role of bias in sighted tests, the audibility of sampling rates, and so forth, as well as with long-established psychoacoustic data such as the Fletcher-Munson curves or the effect of psychoacoustic masking. Also with well-known and measured phenomena like the nonlinearity of air, and perhaps research into our sensitivity to the timing of transients. So if someone is curious, they're welcome to ask, but in general, I've been impressed by the knowledge of many here, indeed, I was introduced in this thread to an important paper of which I hadn't even been aware.

In other cases, people might not be familiar with the study, e.g., my statement to the effect that two op amps can be successfully ABX'd was based on an experiment conducted on Hydrogen Audio, while my statement about the audibility of very low levels of crossover notch distortion was based on what John Siau told me when we discussed the AHB2 at an AES convention a couple of years ago. (I've also participated in experiments in which one listens to varying levels of crossover distortion and while they were not systematic they gave me a subjective appreciation of its sonic signature and just how audible it is).

Beyond that, there is much that isn't widely known because it's proprietary or hasn't been published. When I was consulting for Sony Classical, for example, I had many hours of conversations with the late David Smith, then director of North American recording activities, about Sony's research into the sonic attributes of digital audio, and their practical experience with the same. Frankly, I learned more from those internal studies and David's experience than I did from reading the AES Journal. Much never gets written up, either because it's proprietary or because no one has the time to do so. So I can tell you that the Stockham converter had missing codes, or that variations in pit geometry led to different pressing of the same CD sounding different, but all too often, this isn't the kind of information that ends up in a journal.

And finally of course there were my own experiments and experience in the studio, and the experience of those I work with in the industry. Even in semi-retirement, I deal with issues like blind testing and the interpretation of measurements every day.

 

[josh358]

No its perfectly true period.

Why do you not have an opinion regarding signals that are above the audible range being inaudible? It's been scientific fact proven by experiment for a very, very long time.

The bandwidth limiting is performed by the anti alias filter in the ADC to comply with the most basic aspects of digital audio recording.

I'm sorry, but I can detect no engineering knowledge here. You seem unable to understand some very straightforward concepts (anti aliasing, duh) but have what appear to be some very naive views about psychoacoustics, e.g., you ask "Why do you not have an opinion regarding signals that are above the audible range being inaudible," which is absurd -- obviously if they are above the inaudible range they are audible in isolation, and just as obviously, they are subject to psychoacoustic masking and so may in practice be inaudible in musical program material.

There's really nothing wrong with not knowing -- I learn myself all the time and if you read what I've said here, I've posed questions repeatedly -- but there is something very wrong with projecting your lack of understanding onto those you don't understand.

It seems always to be those who know the least who insult the most.

 

[March Audio]

I'm sorry, but I can detect no engineering knowledge here. You seem unable to understand some very straightforward concepts (anti aliasing, duh) but have what appear to be some very naive views about psychoacoustics, e.g., you ask "Why do you not have an opinion regarding signals that are above the audible range being inaudible," which is absurd -- obviously if they are above the inaudible range they are audible in isolation, and just as obviously, they are subject to psychoacoustic masking and so may in practice be inaudible in musical program material.

There's really nothing wrong with not knowing -- I learn myself all the time and if you read what I've said here, I've posed questions repeatedly -- but there is something very wrong with projecting your lack of understanding onto those you don't understand.

It seems always to be those who know the least who insult the most.

You haven't provided one shred of scientific or engineering information to support anything you have claimed thus far whereas I have done quite the opposite. I understand anti aliasing filtering perfectly well thank you very much. It is clearly yourself who lacks the technical knowledge to discuss the subject. Saying "I had a conversation with person X" doesn't provide credibility to anything you say I'm afraid.

The point regarding signals above the audible range was meant to be absurd. You were saying that they could be, which is clearly.... well.... absurd.

The irony of your post here regarding both technical knowledge and being insulting beggars belief and completely vindicates my earlier view to put put you on ignore.

 

[pozz]

Audio is littered with the bones of equipment that measured great and sounded awful because at the time the measurements were made, we didn't know enough to measure the right things. Indeed, many of the routine measurements that we used today, e.g., jitter rejection, were developed precisely because the measurements we were using proved inadequate.

If I have the history right, in the digital domain the jitter concept was developed before its application to audio. Not to say though that others weren't created because they were prompted by hearing something off (e.g., IMD).

There are plenty of engineers who talk about having acuity down to 0.25dB or 0.1dB. I'm not sure I believe them, at least not that they can do so consistently. There have been enough times I've turned a knob only to find out I was adjusting the wrong channel. That was enough to convince me I should temper myself, allow a fair margin of error and do the work more calmly.

I'm not trying to say you didn't hear what you heard with the Parasound. One thing that actually stands out during listening is that higher distortion sounds like "excitement". But here I'm talking about my experience with high-level differences in transducers, not components. So what you're saying is plausible, kind of, in the sense that I see the what the reasoning could be and some possible evidence for it. In your position I would leave it at just that, though. Especially since the conversation is about two excellent pieces of gear.

 

[LTig]

[..]The Lavry AD122 96 has a strong reputation for the saturation processing it uses on clipping signals during recording (kind of like tape), for example, and then there are loads of things said about compressors, EQs, filters, mixers, etc.

This ADC is more a kind of sound processor than a transparent ADC. If this is desired for the recording fine with me.

 

[pozz]

This ADC is more a kind of sound processor than a transparent ADC. If this is desired for the recording fine with me.

Agreed. But many look at that saturation as being preferable to clipping and therefore more "transparent" overall.

 

[badboygolf16v]

Simple questions: Do you get excited when listening to certain recordings? How many times does it happen in a week when listening to music?

I can have completely different emotional response to the same music with the same equipment. It depends on how *I* am feeling and not on things such as the distribution of harmonic distortion in my playback chain.

 

[March Audio]

If I have the history right, in the digital domain the jitter concept was developed before its application to audio. Not to say though that others weren't created because they were prompted by hearing something off (e.g., IMD).

There are plenty of engineers who talk about having acuity down to 0.25dB or 0.1dB. I'm not sure I believe them, at least not that they can do so consistently. There have been enough times I've turned a knob only to find out I was adjusting the wrong channel. That was enough to convince me I should temper myself, allow a fair margin of error and do the work more calmly.

I'm not trying to say you didn't hear what you heard with the Parasound. One thing that actually stands out during listening is that higher distortion sounds like "excitement". But here I'm talking about my experience with high-level differences in transducers, not components. So what you're saying is plausible, kind of, in the sense that I see the what the reasoning could be and some possible evidence for it. In your position I would leave it at just that, though. Especially since the conversation is about two excellent pieces of gear.

Looking at the subjective effects of jitter is nothing new. A BBC R&D report from 1974. In the references a mention of a report from 1963 was made. So clearly known about from the earliest digital audio work.

https://www.bbc.co.uk/rd/publications/rdreport_1974_11

 

[GrimSurfer]

I'm not sure what you're saying here. The quote "Really, if measurements were telling us the full story about DAC's they all would sound pretty much the same, so much of what's in the graphs is below the threshold of hearing!" implies exactly the same thing. So let me try to clarify my point. I'm saying that when I apply what I know of psychoacoustics to Amirm's measurements, most of them would appear to be below the threshold of hearing, which is about -10 dB SPL in the midrange and in practice somewhat higher since a quiet room might have ambient noise of 40 dB SPL and research suggests that we can hear about 10 dB below the noise floor.

That being the case, one hypothesis is that not everything of significance is being measured. In some cases, I know this is true. For example, I've mentioned the underdamped filters in ESS DAC's, and it's easy to measure transient response. We know as well what underdamping, overdamping, and critical damping sound like, since we've had a lot of experience. So that would have to be measured.

In any case, in no case have I suggested throwing out the measurements that we have! I wouldn't read this site if I weren't interested in the measurements, and their correlation with what we hear. But I've seen Amrin wonder whether a certain measurement was audible because it was of such low magnitude, and I have the same question. I have to suspect that when we measure something that's 90 or 115 dB down it's audible contribution is insignificant and that when we do hear differences, we're hearing something else. But in many other cases, I just don't know. Is that ESS IM hump audible, for example, on music and with real world transducers, and under what circumstances?

I've found that establishing a correlation between measurement and audibility is a lot harder than some here seem to assume. If you talk to a designer, someone who has spent time in the lab measuring and listening, you'll learn a lot, at least I do. I had a very interesting conversation with John Siau at an AES convention a couple of years ago, for example, in which he discussed the effect of non-linear distortion on the reproduction of piano. I think you'd be surprised at how much there is to learn about what matters, and what does not.

What I'm saying is that you have to go with the most accurate and reliable data you have. Audibility varies greatly between individuals, so using this (or the views of people in the business of selling stuff) as the metre for performance is unwise.

As for ESS, I don't think this is the subject of the thread I joined. I have no strong views either way on that subject.

 

[LTig]

[..]... it's well known that the nonlinearity of air alone can make ultrasonic sounds audible.

Do you know at which levels of SPL of ultrasonic sounds the mix products within the audible frequency range become audible?

 

[pozz]

For example, Nelson Pass discovered a few years ago that the addition of third harmonic increases the sense of depth, but only if it's added out of phase.

This is really interesting. Is this documented? If it's true then that technique should be used in the studio instead of the playback chain.

 

[LTig]

Beyond that, there is much that isn't widely known because it's proprietary or hasn't been published. When I was consulting for Sony Classical, for example, I had many hours of conversations with the late David Smith, then director of North American recording activities, about Sony's research into the sonic attributes of digital audio, and their practical experience with the same. Frankly, I learned more from those internal studies and David's experience than I did from reading the AES Journal. Much never gets written up, either because it's proprietary or because no one has the time to do so. So I can tell you that the Stockham converter had missing codes,

We should never forget that companies like Sony and Philips are both active in selling audio equipment and selling music, so people working in one business are not free to talk because what they say may harm the other business.

or that variations in pit geometry led to different pressing of the same CD sounding different, but all too often, this isn't the kind of information that ends up in a journal.

This is something I do not understand, at least not as long as I think that I know how a CD-player works internally.

 

[GrimSurfer]

This is really interesting. Is this documented? If it's true then that technique should be used in the studio instead of the playback chain.

I find it interesting when people quote industry figures, etc without considering the following:

1. They're trying to get ahead criticism of their products by suggesting or saying that certain measurable phenomena are good (when they actually may be bad);

2. They're attempting to mislead competitors willing to take their statements as gospel;

3. They THINK something, but don't necessarily know whether what they are saying is true of not; or

4. They simply don't know what they're talking about.

Before anyone jumps on some perceived slight to the reputation of their favourite audio designer, please note that what I'm offering are variations on null hypotheses that a critical reader may wish to consider before accepting any statements on face value.

Not everyone here is an audio or electronics expert. Nor do we all have golden ears. Yet we all share the same capacity for critical thinking skills.

This isn't directed at pozz. It's directed at people incapable of explaining their POV without relying on the statements of others whose work is neither scientifically proven nor critically peer reviewed.

 

[Xulonn]

or that variations in pit geometry led to different pressing of the same CD sounding different, but all too often, this isn't the kind of information that ends up in a journal.

This is something I do not understand, at least not as long as I think that I know how a CD-player works internally.

A very strange idea - it implies that bits are not just bits, and that there are variations in the "quality" of bits in the digital domain. I am not an engineer, but I thought bits are bits, and nothing more. (Unless pit geometry flaws lead to missing bits, e.g. lost information to the extent that error correction cannot recover it.)

 

[GrimSurfer]

A very strange idea - it implies that bits are not just bits, and that there are variations in the "quality" of bits in the digital domain. I am not an engineer, but I thought bits are bits, and nothing more. (Unless pit geometry flaws lead to missing bits, e.g. lost information to the extent that error correction cannot recover it.)

I agree this is very strange. I always thought that variations in pressings were explained by the use of different master material (actual master tapes are locked away, the industry distributes multiple copies of masters to its pressing facilities worldwide), different mixes or different levels. Some pressings are of better quality though. These can be read more easily without a reliance re-reading or error correction protocols. How this affects SQ is debatable since, short of synch errors, it is still zeros and ones.

The notion of "the same CD" from different pressing facilities is incorrect. Indeed, that's why the industry applies unique product codes to them and marks them in such a way that purchasers can easily choose the exact pressing they want.

I can't recall seeing articles in scientific journals about this but there are databases that show certain sonic differences between pressings. These are typically based on compression, which suggests changes in the mastering material or levels used for a particular pressing.

 

[josh358]

You haven't provided one shred of scientific or engineering information to support anything you have claimed thus far whereas I have done quite the opposite. I understand anti aliasing filtering perfectly well thank you very much. It is clearly yourself who lacks the technical knowledge to discuss the subject. Saying "I had a conversation with person X" doesn't provide credibility to anything you say I'm afraid.

The point regarding signals above the audible range was meant to be absurd. You were saying that they could be, which is clearly.... well.... absurd.

The irony of your post here regarding both technical knowledge and being insulting beggars belief and completely vindicates my earlier view to put put you on ignore.

So go ahead, thanks for the conversation and you're welcome to put me on ignore. There are some impressively knowledgeable people here; I'll gladly discuss things with them, but I'm not inclined to waste time on ad hominem arguments.

 

[gvl]

Josh should try the Blumlein's 8th ADC/DAC copy challenge, don't click on "Spoiler" until you have the results. The DAC in question is based on the 9038 ESS mobile chip, and by my ear it (I have a version of the same DAC) has some "glare" compared to others I heard.

https://www.audiosciencereview.com/...-choose-the-8th-generation-digital-copy.6827/