[pila405]

Most spec sheets list a single figure for THD. I was under the impression that this figure represents distortion at 1kHz, which sits at the most sensitive spot of human hearing. THD can be expressed either as a percentage or an amount of attenuation in dB. 1% THD is -40dB, .5% is -46dB and .1 is -60dB. That rating is established with test tones, but distortion in test tones is not really reflective of the real world impact of distortion on music. In the experiment by Ethan Winer (see the link in my sig file) he takes a horrible buzzing sound- the absolute worst thing you could mix with music- and drops it a bit at a time under the music until it is inaudible. By the time it gets to -40dB, there is no way it can be heard except in the total silence between tracks, which would be totally silent if the buzzing sound was distortion and not noise.

Audiophiles often overstate the importance of distortion when it's a number on a page, yet they can't hear it in practice. I see numbers like .1% being thrown around in audiophile circles as being the minimum acceptable THD, while they wax rhapsodic over the sound of LP records that have distortion levels of as much as 3-4% (-30dB) at the inner groove. The truth is, with digital audio and solid state electronics, distortion isn't really an issue. Even cheap electronics has distortion levels far below audibility. And that's true for just about all specs... response, timing, crosstalk, etc. Distortion isn't much of an issue with most headphones either. It is relatively simple to minimize distortion with the small drivers in headphones. Are there any headphones with THD over 1%? I don't think I've ever run across any. Response is MUCH more important there. Distortion might be more of an issue with speakers, but again, that is dwarfed by the importance of a balanced response.

I might be wrong, but it seems that an awful lot of discussion in audiophile circles is about theoretical things that really don't matter a heck of a lot when someone sits down to listen to Mozart in their living room.

True that many manufacturers do a half-assed job and don't provide enough information about the system they sell. But some do:
https://www.tpdz.net/productinfo/645180.html
https://drop.com/buy/drop-thx-aaa-789-linear-amplifier/details#details (here the THD section is indeed @1kHz, but at least they specify it)

When you look at a system you don't want it to perform just well enough so you won't be able to hear all the noise and distortion in best-case scenarios, but also know that even at worst case, it will still be completely transparent. And with the technology available today, no manufacture has a good argument as to why they shouldn't be able to achieve it and provide the customer with a complete set of specifications.

And again, once the gear is transparent, I don't understand why reviewers feel obliged to indicate these imagined differences. (And to call ESS ISPs\DACs "scratchy" and other non-sense)

 

[bigshot]

Yeah, that is what I have noticed. There is no excuse for a DAC or amp not to be transparent. Every one I've ever bought since the early 80s has been transparent. I don't get the urge to try to keep slicing the pie thinner and thinner. "This amp is even MORE perfect than this perfect amp over here..." That's when I start wondering if the whole thing is just marketing and they are trying to get us to think that split hairs are huge deals. I'm not normally a conspiracy theorist, but the audiophile community seems like a closed loop of advertorial sometimes, and the irony is that the customers themselves do most of the advertising.

I have players with several different DACs inside. For the life of me I can't tell any difference between my iPhone and the Sabre DAC in my Oppo. But every review I read claims a big difference. I've gotten to the point where I assume reviewers are full of excrement unless they prove to me that they aren't.

 

[pila405]

I don't know if I completely agree in this regard. I know that I bought in recent years some amps\DAcs that had various problems, not all had to do with sonic performance.
But even some amps which were supposed to be good, didn't have low enough noise for very sensitive IEMs, or didn't provide enough power to drive fully some harder-to-drive headphones (I listen to classical music mostly, where the dynamic range a lot of the time is quite large and most of the recording is at low volume and even the peaks have some big buffer from 0db)
For DACs - some might just not be reliable enough in terms of connectors\connection, and even though it should be something very basic, no measurements are provided here. I don't care about high-res audio much and don't listen to DSD\MQA at all, so this makes things easier. Some, mostly up to a few years ago, didn't provide clean signal from the USB if you had a noisy source (PC) and it was very audible.
So in general, I think there are some note-worthy improvements even in recent years. And in terms of "better transparency over what's already transparent", I find even the engineering by itself intriguing enough.

In terms of reviews - I agree that 99% of the reviews out there are complete time-waste to read, especially when you have sites which provide you with a full set of measurements.

 

[bigshot]

Yes, impedance issues with IEMs are separate from what I'm talking about. Those amps would work fine with standard headphones. The problem there is the wrong tool for the job, not a defective tool. And PCs with noisy USB are noisy. Again, with a proper comp, it wouldn't be noisy. The source of the problem isn't the DAC or amp. It's the transducers or source being used with the wrong DAC or amp.

 

[pila405]

Indeed, but today you have amps which can do perfect work with whatever you throw at them, like the A30Pro I use currently. You have a huge headroom in terms of power and the noise floor is so low you can't hear any background no matter how sensitive your earphones are. Also impedance is low enough to not affect FR for all the headphones\earphones i'm familiar with.

 

[bigshot]

I have headphones that sound great without any amp at all. That doesn't mean that headphones that require amping are defective.

 

[pila405]

What? I don't think I understand the context for this

 

[bigshot]

You said that there are amps that work with everything as an argument to say that it is the amp's fault if it is noisy with non-standard IEMs. An amp that does perfect with anything you throw at them isn't even necessary if you have headphones that do perfect without an amp. Maybe it's the IEMs fault that they don't work without an amp then too.

My point is that you can't argue that there is something wrong with the amp because it doesn't work with IEMs it isn't intended to work with. With normal headphones, the amp would be transparent. With IEMs that it was never intended to be used with it's noisy. That isn't the fault of the amp, and it doesn't mean it is a "noisy amp". It's just picking the wrong tools for the job.

I agree with you that simpler is better. But I would achieve that by not using IEMs with non-standard impedance, and not using an amp when an iPhone and headphones designed to work perfectly without an amp are available. But I'm not saying there is anything wrong with the IEMs or the amp designed to be used with them. They work fine for what they are designed to do.

Is that clearer?

 

[ADUHF]

This week's livestream is up.



The meatier stuff begins at around 1:27:50 or thereabouts. Some memorable quotes from this stream...

"You have to compare it to other stuff." (this was in reference to doing headphone reviews)
"If you can hear it, it's measurable."
"If you don't do comparisons, it's an ad."

Agree/disagree with any of the above?

 

[ADUHF]

"There have been a number of studies that demonstrate that even at fairly high levels of THD that did not have any correlation with listener preference."
This is just completely misleadingly worded. It's not technically wrong as he is referring to 1% distortions (which is only added as a sidenote and not clearly articulated in the argument) that did not correlate. In fact the paper shows that THD does correlate to subjective listener impressions! For the headphones that showed highest THD below 100Hz and above 1kHz the subjective commentary matched the measurement. This is however not addressed at all in the video. There are bits and pieces taken from the paper that support the claim, but the bits and pieces that oppose the claim in the same paper are conveniently left out. To me that is just not acceptable.

When you say this was not mentioned in the video, I assume you're referring to Resolve's video on SINAD and why he thinks it's not that important.

This was mentioned though in the presentation given by Temme and Olive on their headphone distortion study. And I've cued the video below to that section, so people can see all the results...



The two headphones which were given the lowest preference ratings by the 8 trained participants in the study (Dr. Olive was one of the participants btw) had the highest THD, below 100 Hz and above 1kHz. The one that received the lowest rating had the highest THD below 100 Hz. And the headphone with the next lowest rating had highest THD above 1 kHz. The same two headphones also had the highest non-coherent distortion (whatever that is).

 

[ADUHF]

Regarding Resolve's video, I find it insincere...

Fwiw, I think he's sincere in his belief that SINAD scores aren't that valuable for things like amps and DACs, for the reasons stated in the video. He has been fairly consistent on this in the live streams.

The Temme/Olive study was for headphones though. And I think Dr. Geddes also gave a somewhat more nuanced opinion on the subject in his video chat with Erin. This subject also came up again in the 2nd half of this week's HP Show livestream above.

The thing that everyone (including Temme, Olive and Geddes) seems to be on the same page on is that some sort of measurement that is more perceptually-based would probably be better. And Geddes discussed some of his ideas along these lines in the video with Erin. Here is that video again, in case anyone missed it.

 

[ADUHF]

"You have to compare it to other stuff." (this was in reference to doing headphone reviews)
"If you can hear it, it's measurable."
"If you don't do comparisons, it's an ad."

I believe that comparisons were the main reason for the existence of Tyll's headphone "Wall of Fame" btw.

 

[bigshot]

Carefully controlled comparisons are the best way to judge sound quality. (blind, level matched, direct A/B switched) Measurements are the best way to measure fidelity. We can measure everything we hear, but we can't hear everything we measure. So, past the point of transparency, it's pointless to spend more on measurable sound you can't hear. Some comparisons are advertisements too. Audiophile reviews are frequently nothing more than advertorial.

The big piece of advice that seems to never be mentioned in audiophile circles is ergonomics and usability. Convenience is MUCH more variable from one DAC or amp to another than sound quality. And comfort is of primary importance with headphones. It doesn't matter how good cans sound if they make your head hurt to wear them. I think reviews should spend more time on ergonomic issues than sound quality or fidelity.

 

[pila405]

"You have to compare it to other stuff." (this was in reference to doing headphone reviews)

Compare yes, but also how? He seems to miss that part many times, unfortunately.

"If you can hear it, it's measurable."

Not always, as has been proven time and time again. Many hear imaginary differences between amps\DACs that do not exist and write about the myriad of differences which are no where to be found. But as @bigshot wrote, if you can hear it in a blind test, than it is indeed measurable.

"If you don't do comparisons, it's an ad."

Many do compare and still provide nothing other than an ad for the manufacturer.

 

[ADUHF]

When you say this was not mentioned in the video, I assume you're referring to Resolve's video on SINAD and why he thinks it's not that important.

This was mentioned though in the presentation given by Temme and Olive on their headphone distortion study. And I've cued the video below to that section, so people can see all the results...



The two headphones which were given the lowest preference ratings by the 8 trained participants in the study (Dr. Olive was one of the participants btw) had the highest THD, below 100 Hz and above 1kHz. The one that received the lowest rating had the highest THD below 100 Hz. And the headphone with the next lowest rating had highest THD above 1 kHz. The same two headphones also had the highest non-coherent distortion (whatever that is).

One other thought I was going to add on this is that correlation doesn't necessarily equal causation. So although the two headphones that were ranked the lowest in preference had the highest THD and non-coherent distortion, it is possible that those were not the reasons for the lower rankings. And that there were other kinds of distortion (which were not covered in the study) that could also have been contributing factors in the low rankings.

I think you also have to be open to the possibility that there could be some kinds of distortion which can potentially result in a more pleasing sound than no distortion at all. And that this could also (possibly) explain why some headphones in the above study received a higher preference rating than the ones with the higher THD and non-coherent distortion.