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#109 |
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Member
Join Date: Dec 2008
Location: Varennes, Québec
Posts: 37
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I once was like you Dave, a DBT believer until I was fool by such a test. ( I think I already talk about this here before).
DBT are contrary to what you think scientifically flaw when they are used for HIFI evaluation. Why? In a scientific experiment, only one parameter is supposed to be change. This is where DBT are inherently flawed, not only does more elements changed they are all changed: different amp, different preamp ( hopefully, it won't be a crappy receiver), different loudspeakers, usually unknown music ( please, no test tone) and worst off all, different room. With such a setting it's no surprise that DBT give always the same result, no difference. I prefer the way David did a bind test. He had changed only one element and didn't tell is friend about it. His friend notice an improvement ( was it?). this is much closer to scientific experiment than the usual DBT that the believers want us to believe. There is one HIFI mag that do something similar, UHfmag. They use a listening panel, and a reference system. A high resolution system that stay the same for a long period of time ( a real reference). When they do there blind test, only one person know what it is ( name, price, etc). Each panelist take notes. Each panelist can ask to listen again to one component. Listening is done over many hours. They use the same procedure for amp, preamp, source and...cables. Most of the times their notes agree but not always. Sometimes manufacturers get ****ed at them because they say it as it is. Some less expensive component performing better than more expensive ones. I remember such a test about cables, where there was a consensus: don't buy the more expensive cable, the chep one is so much better ( it was the same company). p.s. Dave, are you related to the troll. it seams that you appeared at about the same time when people were telling about his different nicknames that he uses. What's more, sometimes your posting happenned right after his, confirming his saying. No offence , just wondering. |
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#110 |
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Member
Join Date: Dec 2008
Location: Varennes, Québec
Posts: 37
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Here's something interesting and it even might be educating for some:
Robert Harley -- Wed, 05/28/2008 - 15:18 The following is my editorial from The Absolute Sound Issue 183 (not yet published) on blind listening tests. The Blind (Mis-) Leading the Blind Every few years, the results of some blind listening test are announced that purportedly “prove” an absurd conclusion. These tests, ironically, say more about the flaws inherent in blind listening tests than about the phenomena in question. The latest in this long history is a double-blind test that, the authors conclude, demonstrates that 44.1kHz/16-bit digital audio is indistinguishable from high-resolution digital. Note the word “indistinguishable.” The authors aren’t saying that high-res digital might sound a little different from Red Book CD but is no better. Or that high-res digital is only slightly better and not worth the additional cost. Rather, they reached the rather startling conclusion that CD-quality audio sounds exactly the same as 96kHz/24-bit PCM and DSD, the encoding scheme used in SACD. That is, under double-blind test conditions, 60 expert listeners over 554 trials couldn’t hear any differences between CD, SACD, and 96/24. The study was published in the September, 2007 Journal of the Audio Engineering Society. I contend that such tests are an indictment of blind listening tests in general because of the patently absurd conclusions to which they lead. A notable example is the blind listening test conducted by Stereo Review that concluded that a pair of Mark Levinson monoblocks, an output-transformerless tubed amplifier, and a $220 Pioneer receiver were all sonically identical. (“Do All Amplifiers Sound the Same?” published in the January, 1987 issue.) Most such tests, including this new CD vs. high-res comparison, are performed not by disinterested experimenters on a quest for the truth but by partisan hacks on a mission to discredit audiophiles. But blind listening tests lead to the wrong conclusions even when the experimenters’ motives are pure. A good example is the listening tests conducted by Swedish Radio (analogous to the BBC) to decide whether one of the low-bit-rate codecs under consideration by the European Broadcast Union was good enough to replace FM broadcasting in Europe. Swedish Radio developed an elaborate listening methodology called “double-blind, triple-stimulus, hidden-reference.” A “subject” (listener) would hear three “objects” (musical presentations); presentation A was always the unprocessed signal, with the listener required to identify if presentation B or C had been processed through the codec. The test involved 60 “expert” listeners spanning 20,000 evaluations over a period of two years. Swedish Radio announced in 1991 that it had narrowed the field to two codecs, and that “both codecs have now reached a level of performance where they fulfill the EBU requirements for a distribution codec.” In other words, Swedish Radio said the codec was good enough to replace analog FM broadcasts in Europe. This decision was based on data gathered during the 20,000 “double-blind, triple-stimulus, hidden-reference” listening trials. (The listening-test methodology and statistical analysis are documented in detail in “Subjective Assessments on Low Bit-Rate Audio Codecs,” by C. Grewin and T. Rydén, published in the proceedings of the 10th International Audio Engineering Society Conference, “Images of Audio.”) After announcing its decision, Swedish Radio sent a tape of music processed by the selected codec to the late Bart Locanthi, an acknowledged expert in digital audio and chairman of an ad hoc committee formed to independently evaluate low-bit rate codecs. Using the same non-blind observational-listening techniques that audiophiles routinely use to evaluate sound quality, Locanthi instantly identified an artifact of the codec. After Locanthi informed Swedish Radio of the artifact (an idle tone at 1.5kHz), listeners at Swedish Radio also instantly heard the distortion. (Locanthi’s account of the episode is documented in an audio recording played at workshop on low-bit-rate codecs at the 91st AES convention.) How is it possible that a single listener, using non-blind observational listening techniques, was able to discover—in less than ten minutes—a distortion that escaped the scrutiny of 60 expert listeners, 20,000 trials conducted over a two-year period, and elaborate “double-blind, triple-stimulus, hidden-reference” methodology, and sophisticated statistical analysis? The answer is that blind listening tests fundamentally distort the listening process and are worthless in determining the audibility of a certain phenomenon. As exemplified by yet another reader letter published in this issue, many people naively assume that blind listening tests are somehow more rigorous and honest than the “single-presentation” observational listening protocols practiced in product reviewing. There’s a common misperception that the undeniable value of blind studies of new drugs, for example, automatically confers utility on blind listening tests. I’ve thought quite a bit about this subject, and written what I hope is a fairly reasoned and in-depth analysis of why blind listening tests are flawed. This analysis is part of a larger statement on critical listening and the conflict between audio “subjectivists” and “objectivists,” which I presented in a paper to the Audio Engineering Society entitled “The Role of Critical Listening in Evaluating Audio Equipment Quality.” You can read the entire paper here http://www.avguide.com/news/2008/05/...pment-quality/. I invite readers to comment on the paper, and discuss blind listening tests, on a special new Forum on AVguide.com. The Forum, called “Evaluation, Testing, Measurement, and Perception,” will explore how to evaluate products, how to report on that evaluation, and link that evaluation to real experience/value. I look forward to hearing your opinions and ideas. Robert Harley |
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#111 | |
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Member
Join Date: Apr 2008
Location: Seattle, Washington
Posts: 64
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Quote:
No, DBT is not inherently flawed. Using a DBT to test more than one parameter at a time is a flawed test design caused by the tester. Yes, DBT should change only one item at a time or a single parameter of an item. That is why I think its difficult to do DBT for equipment, too many variables.Everything has to be set identically. That would have to include not only tone conrols, but Dolby, etc etc., and, say, with preamps or receivers, are those chips and augmentations identical? Not likely Who can afford to run a lot of tested between, say, amps. All the amps being considered would have to be there, that would be expensive and a hassle. I did do a DBT for Bob Carver once, after first just listening to one, then the other, while knowing which was which. The DBT had a surprising result, which gave more credence to the DBT . Cables are MUCH easier to test with DBT thatn, say, amps, preamps, speakers. A bunch of cables can be tested without a huge hassle. I am particularly in favor of such tests for cables because of the hype and the ridiculous expense and profiteering, not to mention the BS. And the fact that the huge amount of money wasted to fill the pockets of modern snake oil purveyors could be well spent on better speakers, where the improvements are much more noticeable anyway. Even if, say, a $1,000.00/meter cable could sound better than a $25.00 monoprice cable, the difference would be very very subtle, otherwise this would not be so controversial in the first place. Even DBT tests by audio magazines reveal that those auditioning just can't hear the difference even if they insisted they could prior to the tests. So, spend the over $900.00 savings on, say, front speakers. The improvement would be very apparent. Then multiply the number of cables by that savings, and you will get such a large sum that could be much better spent on speakers, that you would have a much improved 5.1 system that anyone could enjoy more!! PS you have used "there" where "their" is the correct term. cheers DAve |
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#112 | |
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Member
Join Date: Dec 2008
Location: Varennes, Québec
Posts: 37
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Quote:
There is one point that we agree: spend where you'll get the most for your money.( And this is not cables) p.s. I rarely reread myself when I write something on the web. ( I've found where the error that you pinpointed is. There are some plural mistakes too) This is not research papers, it's only a forum. My L1 is not English but French. English is my L2. Last edited by Daniel-a; 02-25-2010 at 09:07 PM.. |
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#113 | |
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Member
Join Date: Feb 2010
Location: Uk
Posts: 7
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Quote:
__________________
Audio Visuals Directory |
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#114 | |||
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Super Member
Join Date: Jun 2007
Location: Washington, DC
Posts: 272
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Quote:
Quote:
(different poster) Quote:
It's astonishing how very fundamentals of empirical testing like this are completely lost on so many who post in the name of "science". |
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