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Decibels, distortion, amplifiers and golden ears - Page 4  

post #46 of 790
Quote:
Originally Posted by Roam View Post
On why THD numbers do not correlate well with perceived sound quality (PDF file) This is a graduate level thesis which was passed and approved by Electrical Engineering professors. It's based on the prior art of tests conducted by the BBC labs decades ago, the results & conclusions of which have unfortunately become lost for the most part in modern hi-fi. To briefly summarize, it's not the THD number which is important, rather, it's the distribution of the harmonic spectra...

...In short, TheVinylRipper should quit using Wikipedia and Google, and pick up some real actual textbooks and testing equipment. Norman Crowhearst's papers would be a good place to start.
I find it unfortunate that the Cheever thesis has found such promenence given its major flaws
what I really think of the Cheever thesis:
http://www.diyaudio.com/forums/showt...0&pagenumber=5

you may have to give up on the idea of the internet as an authoritative source in many scientific fields, JAES, ASA, in fact most peer reviewed journals don't put their content online for free, not that there isn't some good psychoacoustic info on the web:
Quote:
Originally Posted by jcx View Post
...I think a highly relevant paper is “Coding High Quality Digital Audio” by a researcher at Meridian:

http://www.meridian-audio.com/lib_pap.htm

The paper is very technical (by head-fi standards at least, it is a “popularization” of a JAES convention paper) and the subject may seem a little off topic but in support of his argument for a particular coding scheme Stuart summarizes some of “conventional” audio engineering/psychoacoustic understanding of human perception limitations and their relation to reproduced audio – you might want to jump to the figures/graphs at the end of the paper and then search back into the text for the explanatory context

Some of the paper’s limits/thresholds of human audio perception would also be useful to consider in amplifier design as well as digital recording/playback
fig. 3, 4 and their discussion in the body of the paper treat "harmonic" distortion audibility


even Stereophile occasionally hints at some sophistication in distortion audibility discussion:
http://stereophile.com/reference/406howard/index1.html


given the superior quality of of the above cited articles, (particularly the Czerwinski I cite a few posts down in the diyAudio thread) I'd really, really like to never see Cheever cited again
post #47 of 790
Quote:
Originally Posted by TheVinylRipper View Post
Good morning everyone.

This may well be my last post/thread here, I strongly suspect that my views upset more than a few of you and that is not my intention at all.

I've been doing a little math and have come to some conclusions that I would like to share.

...

I welcome discussion on this subject.

As I said at the beginning, my intention is not to cause anyone to become upset, it is rather to introduce some rationality into what I see as a somewhat irrational fixation on ever and ever better specs on amplification and/or DAC's.
I agree that the distortion produced by the transducer is the weakest link. But I have to disagree with the rest of the analysis.

Firstly, you assume the test is accurate. I happen to think it's flawed.

1.The sound quality of the samples is far too low (I estimate 96kbps MP3 or worse). This inevitably results in lower SNR and resolution overall, among other things. Therefore the results in this test can't be assumed to be the valid with regard to full quality audio, such as CD or SACD.

2. The interface is badly designed. Concentrated listening produces better results with the eyes closed. There's no way to do the test with one's eyes closed (ie. with the keyboard).

3. The samples themselves are poorly selected. For example, for the Pop test, there is a loud clicking noise at the beginning of the sample. This click has the effect of precipitating a kind of change blindness in terms of audio, where the click serves as the disruption, thereby reducing the listener's awareness of the differences between the currently playing and previously played samples.

4. Looking at the results, it's likely the test software itself has a fault somewhere:



At -45dB, the results should not jump to almost the level of the median. The same jump at -45dB occurs in the Pop test as well.

I for one didn't post my results on that thread because it was obvious that it would lead to one-upmanship. There's nothing stopping anyone from posting any number they wish, and no way to verify the results. So, no reliable conclusions about head-fi can be drawn from those posts.

Simply invoking equations doesn't validate the reasoning behind them. Maybe if a better designed test was created - one in which we could seperate the head-fi results from the rest - we could get a better idea of how well we hear. Until then, just enjoy the music.
post #48 of 790
Quote:
Originally Posted by b0dhi View Post
1.The sound quality of the samples is far too low (I estimate 96kbps MP3 or worse). This inevitably results in lower SNR and resolution overall, among other things. Therefore the results in this test can't be assumed to be the valid with regard to full quality audio, such as CD or SACD.
This is extremely true. Lowering resolution of the file that much generally reduces the frequencies we are talking of here, which at the same time becomes highly impractical. Majority of solidstate amplification will distort alot exclusively in the high frequency range (how high depends on the bandwidth, and higher quality amplifiers will exhibit alot less of that). When we are talking about low resolution files, we cannot simulate that distortion, and frankly my guess is that by not even covering majority of the frequency range, we are leaving out areas where human ears can be more sensitive. And .01% THD at 1 KHZ is one thing, now being able to say .01% THD at 20-20 is a different thing. Many cheaper amplifiers will skyrocket with measured distortion past 16 khz (hell, some op-amps I was testing for EE labs became useless around 12 khz).

Amen, that is a speculation, I do not know how sensitive ears are depending on the frequency, hopefully someone can correct me here.
post #49 of 790
Quote:
Originally Posted by jcx View Post
I find it unfortunate that the Cheever thesis has found such promenence given its major flaws
what I really think of the Cheever thesis:
http://www.diyaudio.com/forums/showt...0&pagenumber=5

you may have to give up on the idea of the internet as an authoritative source in many scientific fields, JAES, ASA, in fact most peer reviewed journals don't put their content online for free, not that there isn't some good psychoacoustic info on the web:
Unfortunately the Cheever paper is about the only one which can be found for free on the web, which I suppose why it's referenced so often. The various audio engineering journals are by subscription only and require fees, though in some cases it's well worth the cost for access to the papers.
post #50 of 790
Thread Starter 
Did anyone else read the rest of information on the site?

It's not as simple as it appears at first glance.

http://www.klippel-listeningtest.de/lt/background.html

"Reference for the Test Method: Kaernbach, C., "Simple adaptive testing with the weighted up-down method", Perception & Psychoacoustics 1991, 49(3), 227-229"

I just had my wife take the test, she has no experience at all as critical listener, she does like music though.

-15 dB.

Same setup as I posted before, TB Santa Cruz playing through an Altec Lansing mulitmedia system with Dolby surround and a decent sub.

A system I got at a thrift store for $10..
post #51 of 790
Thread Starter 
Quote:
Originally Posted by b0dhi View Post
I agree that the distortion produced by the transducer is the weakest link. But I have to disagree with the rest of the analysis.

Firstly, you assume the test is accurate. I happen to think it's flawed.

1.The sound quality of the samples is far too low (I estimate 96kbps MP3 or worse). This inevitably results in lower SNR and resolution overall, among other things. Therefore the results in this test can't be assumed to be the valid with regard to full quality audio, such as CD or SACD.
You estimate...

Quote:
2. The interface is badly designed. Concentrated listening produces better results with the eyes closed. There's no way to do the test with one's eyes closed (ie. with the keyboard).
One can concentrate, then open the eyes, click on the next selection.

If you say that makes the test invalid because it breaks the concentration then I would invoke the fact that memory for sound is poor.

Quote:
3. The samples themselves are poorly selected. For example, for the Pop test, there is a loud clicking noise at the beginning of the sample. This click has the effect of precipitating a kind of change blindness in terms of audio, where the click serves as the disruption, thereby reducing the listener's awareness of the differences between the currently playing and previously played samples.
That could be an artifact of your system, I heard no such clicking and I was listening quite carefully.

Quote:
4. Looking at the results, it's likely the test software itself has a fault somewhere:



At -45dB, the results should not jump to almost the level of the median. The same jump at -45dB occurs in the Pop test as well.
Perhaps the most skilled listeners with the best ears made it all the way down. My hearing is rather poor and I made -36 dB.

Quote:
I for one didn't post my results on that thread because it was obvious that it would lead to one-upmanship. There's nothing stopping anyone from posting any number they wish, and no way to verify the results. So, no reliable conclusions about head-fi can be drawn from those posts.
You think that people would post a *worse* score than they made?

I got the impression that a lot of people were surprised and disappointed at how poorly they did.

Quote:
Simply invoking equations doesn't validate the reasoning behind them. Maybe if a better designed test was created - one in which we could seperate the head-fi results from the rest - we could get a better idea of how well we hear. Until then, just enjoy the music.
You have yet to state a valid critique of my reasoning.

If you have one, let's hear it.
post #52 of 790
What's the upshot for the newly initiated here, who you say you are looking out for their interest? Would you be suggesting a Sony Diskman > Boosteroo > HD-580s ?

BTW, would you answer the question previously presented with reference to your medical insurance / health issues, and what that info was presented in support of ?
post #53 of 790
Thread Starter 
Quote:
Originally Posted by Hi-Finthen View Post
What's the upshot for the newly initiated here, who you say you are looking out for their interest? Would you be suggesting a Sony Diskman > Boosteroo > HD-580s ?

BTW, would you answer the question previously presented with reference to your medical insurance / health issues, and what that info was presented in support of ?
You might want to read the thead, I already answered that.

But here goes, you never know when disaster is going to strike, it is impossible to predict the future.

It is best not to spend too much on essentially frivolous things like hobbies.

I have already seen at least two people on headfi selling their cherished gear due to financial setbacks. And a few more chipping in saying they had to do so also.

Get the most bang for the buck, shop, shop, shop and research what you buy throughly.

I have no idea what a Boosteroo is although I suspect it is a cheap amp.

I have a fifteen year old Kenwood portable CD player. It still sounds just fine.
post #54 of 790
Quote:
Originally Posted by TheVinylRipper View Post
I have no idea what a Boosteroo is although I suspect it is a cheap amp.
It is. It's also the reference that Hi-Finthen recycles whenever he wants to make a condescending remark about someone else's gear or hearing ability.
post #55 of 790
So, why are you posting on Head-Fi? Everyone is perfectly happy with their hobby. You obviously see things a lot different than everyone else. So, why continue to post?
post #56 of 790
Quote:
Originally Posted by Febs View Post
It is. It's also the reference that Hi-Finthen recycles whenever he wants to make a condescending remark about someone else's gear or hearing ability.
No, not trying to be condescending about less costly gear, however this same old tired subject replays with the upshot that CDPs sound all the same and a Sony Diskman is the suggested CDP; As well as all amplifiers sound the same, may as well buy the least expensive etc... This conclusion is usually made with the same old test your hearing B.S. , when it is not for us to prove our hearing when it is that I do hear differences and improvements inline with the price paid for audio gear... Those who claim not to hear differences in fact are the ears which need testing, is all I'm saying

Where is Hciman77, he usually rolls in about now
post #57 of 790
Thread Starter 
Quote:
Originally Posted by jellybones View Post
So, why are you posting on Head-Fi? Everyone is perfectly happy with their hobby. You obviously see things a lot different than everyone else. So, why continue to post?
For one thing, I am learning.

I learned about orthodynamic phones and have a pair on the way.

I've learned a lot about electrostatics and electrets, something else which interests me.

I enjoy giving advice in a field in which I have some small degree of expertise.

I was once a n00b and there was nothing like the internet to turn to for information. It was all from magazines which had a vested interest in keeping their advertisers happy.

My first pair of serious speakers I bought in 1968, I attended a HiFi show and noticed that one particular model of speaker was being used by a lot of the exhibitors that were selling something other than speakers.

Those were the ones I bought, figuring that the other exhibitors would use the best available in order to put their product in the best light.

I wasn't unhappy with the result.
post #58 of 790
Thread Starter 
Quote:
Originally Posted by Hi-Finthen View Post
No, not trying to be condescending about less costly gear, however this same old tired subject replays with the upshot that CDPs sound all the same and a Sony Diskman is the suggested CDP; As well as all amplifiers sound the same, may as well buy the least expensive etc... This conclusion is usually made with the same old test your hearing B.S. , when it is not for us to prove our hearing when it is that I do hear differences and improvements inline with the price paid for audio gear... Those who claim not to hear differences in fact are the ears which need testing, is all I'm saying

Where is Hciman77, he usually rolls in about now
I've been doing audio for forty years now, it's my experience that price isn't all that good an indicator of performance.

A huge amount of what is sold is driven by the marketing department and not the engineers.

Go and read Dilbert, Scott Adams bases it on real life stories his readers send to him. Dilbert is an engineer and usually the last one anyone actually listens to.

I've been involved with product development a couple of times.. Marketing says they want this, this and that, and oh by the way they want it yesterday and oh yes, it has to be cheap too.. Maximize profits for the stockholders don'tcha know.

Cheap, quick, good ... Pick any two..
post #59 of 790
I'll take quick and good thanks.
post #60 of 790
Thread Starter 
Quote:
Originally Posted by Computerpro3 View Post
I'll take quick and good thanks.
Good for you.

An individual decision that I have no problem with.

Not everyone has a large disposable income, those are the ones that I am speaking to.

You can have good sound without paying exorbitant amounts of money.

Everyone who comes to my home when I'm playing music remarks on how good my system sounds. Tight yet deep bass, crystalline highs and a warm midrange (my speakers have a 3" dome midrange).

The great majority have spent several times what I have spent and yet have inferior sound.

One word: Bose..
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