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Testing audiophile claims and myths - Page 130

post #1936 of 2869

He doesn't say that all the amps have the same power rating.

post #1937 of 2869

Looking through the Amp Challenge by Clark ..(first page). In his testing criteria he uses EQ to match the frequency response of the amps he tests. But wouldn't that invalidate his test results? Correcting deficiencies before the test and then testing the lack of deficiencies ..

 

What are your thoughts?

post #1938 of 2869
Quote:
Originally Posted by Yahzi View Post

Looking through the Amp Challenge by Clark ..(first page). In his testing criteria he uses EQ to match the frequency response of the amps he tests. But wouldn't that invalidate his test results? Correcting deficiencies before the test and then testing the lack of deficiencies ..

 

What are your thoughts?

 

He's not trying to make the same point that some others are.  Paraphrasing, his position would be more that amps sound the same aside from any frequency response differences (if they exist) and while not being driven into clipping.

 

Actually, the majority of amps would have a flat response, so there would be no need to EQ.

 

There are performance differences other than frequency response between different amps (other than output power levels as well), but these seem to have a relatively smaller impact on the sound, such that people that have taken the test could not distinguish between amps with very high probability.  That said, the setup is more difficult on the listener (hard to tell differences) than some other blind tests.  To give the listener more advantages, one would let the listener switch between amps by their own controls, maybe use some better speakers and room, possibly turn up the volume, and so on.  With a different procedure and setup, for example, it might be readily possible to distinguish an amp with significantly higher distortion than another, even if the frequency responses are matched.  Null results are always inconclusive on alternate possibilities and explanations; that said, that doesn't mean that we should be treating every possibility seriously, if they are ridiculous.

 

Anyway, it just seems to show that any differences other than frequency response definitely do not make "night and day" differences, or else people would have been able to pass the test.

post #1939 of 2869
Quote:
Originally Posted by mikeaj View Post

 

He's not trying to make the same point that some others are.  Paraphrasing, his position would be more that amps sound the same aside from any frequency response differences (if they exist) and while not being driven into clipping.

 

Actually, the majority of amps would have a flat response, so there would be no need to EQ.

 

There are performance differences other than frequency response between different amps (other than output power levels as well), but these seem to have a relatively smaller impact on the sound, such that people that have taken the test could not distinguish between amps with very high probability.  That said, the setup is more difficult on the listener (hard to tell differences) than some other blind tests.  To give the listener more advantages, one would let the listener switch between amps by their own controls, maybe use some better speakers and room, possibly turn up the volume, and so on.  With a different procedure and setup, for example, it might be readily possible to distinguish an amp with significantly higher distortion than another, even if the frequency responses are matched.  Null results are always inconclusive on alternate possibilities and explanations; that said, that doesn't mean that we should be treating every possibility seriously, if they are ridiculous.

 

Anyway, it just seems to show that any differences other than frequency response definitely do not make "night and day" differences, or else people would have been able to pass the test.

 



If you read this link, http://tom-morrow-land.com/tests/ampchall/index.htm

the listener controls pretty much all the parameters and can, for example, substitute speakers or source. Here is the precis version of the test procedure:

Testing procedure

The testing uses an ABX test device where the listener can switch between hearing amplifier A, amplifier B, and a randomly generated amplifier X which is either A or B. The listener's job is to decide whether source X sounds like A or B. The listener inputs their guess into a computerized scoring system, and they go on to the next identification. The listener can control the volume, within the linear (non-clipped) range of the amps. The listener has full control over the CD player as well. The listener can take as long as they want to switch back and forth between A, B, and X at will.

Passing the test requires two sets of 12 correct identifications, for a total of 24 correct identifications. To speed things up, a preliminary round of 8 identifications, sometimes done without levels or other parameters perfectly matched, is a prerequisite.

Richard Clark normally has CD source, amplifiers, high quality home audio speakers, and listening environment set up in advance. But if the listener requests, they can substitute whatever source, source material, amplifiers, speakers (even headphones), and listening environment they prefer, within stipulated practical limits. The source material must be commercially available music, not test signals. Richard Clark stipulates that the amplifiers must be brand name, standard production, linear voltage amplifiers, and they must not fail (e.g. thermal shutdown) during the test.

 

post #1940 of 2869
Quote:
Originally Posted by Roly1650 View Post

If you read this link, http://tom-morrow-land.com/tests/ampchall/index.htm

the listener controls pretty much all the parameters and can, for example, substitute speakers or source. Here is the precis version of the test procedure:

 

My bad, been a while since I looked through all the details.

 

But this doesn't particularly seem to add up, if the test was often administered to large groups of people?  (I'm sure that's how the "thousands of people" came about.)  How many individuals were controlling the ABX switcher themselves, with good equipment and environmental conditions, etc.?  How many people scored better than say p=0.05 but not at the level required to pass—higher than 5% of participants?  Is the detection rate close to 50% or just not in the very significant range for each person?  Info seems to be missing.

 

The fact that there were individual challengers on ABX setup (how many?  doesn't seem like a popular thing for many to try, especially considering the cost) does imply something, though.

 

 

I wonder if anybody tried to rig this by selecting the right amp, or if that would be screened out.  e.g. build something to spec that passes the requirements but has high crossover distortion.


Edited by mikeaj - 3/1/13 at 11:13am
post #1941 of 2869

Was having an argument with a buddy over IB and in-wall. He seems to be saying that a speaker mounted flush in a wall is the same thing as an infinite baffle. Is that really true? I thought an IB was a system where the woofers were operating in free air. I don't think placing a speaker flush in a wall does that. Correct me if I'm wrong.

post #1942 of 2869
Quote:
Originally Posted by Yahzi View Post

Was having an argument with a buddy over IB and in-wall. He seems to be saying that a speaker mounted flush in a wall is the same thing as an infinite baffle. Is that really true? I thought an IB was a system where the woofers were operating in free air. I don't think placing a speaker flush in a wall does that. Correct me if I'm wrong.

Depends on the speaker and the wall.  Some in-walls have well defined back boxes, sometimes the back box is formed by the wall cavity, and if the cavity isn't sealed it's sort of a badly tuned port...ok, not really.  The come closest to a sealed box, usually. In-ceiling is different if it's a drop ceiling.  That's more of an IB. 

 

Most in walls are designed to work with subs, so the bass response of the speaker isn't all that critical. But one advantage of the in wall is that it take early reflections off the wall to nearly zero because it's flush.

post #1943 of 2869

The speaker in question is ported. I just don't know how a flush in-wall ported speaker can behave as if it were in free air. Perhaps I'm wrong.

post #1944 of 2869

Something like this :

 

post #1945 of 2869

Well, a ported speaker is (hopefully) precisely tuned to operate in it's box with the port.  Putting it flush in a wall won't change that, but it does two things.  Eliminates reflections off the front wall, and places the origin of bass waves at the wall...sort of the idea of the THX wall in cinemas. But I don't see anything infinite about it.

post #1946 of 2869
You had to post this....now I want to refinish my basement. smily_headphones1.gif
Quote:
Originally Posted by Yahzi View Post

Something like this :

Music-Studio-Interior-Design-1.jpg
post #1947 of 2869

An Infinite Baffle loudspeaker requires an extremely large enclosure (like the size of a room) that's why it's called "Infinite".

post #1948 of 2869
I was reading about this test on another part of the forum:

The Audio Society of Minnesota Conducts Cable Comparison Tests

What Prog Rock said on the original post makes sense, but I would like your take on this as well:

"The resulst are very mixed with no cable making any clear difference. They accept there is no objective difference, but since there is a difference found which can easily be expalined by random selection, they conclude a subjective difference is there and so allegedly "cable do make a difference"."

Cheers,
Leo
post #1949 of 2869

By stereophile's logic, statistically insignificant results prove that there are differences because the percentage of "preference" of one cable was slightly higher? Just another article that shows their incompetence and patently absurd conclusions.

Of course they didn't mention that the $ 8000 cable "scored" almost as bad as the $ 3 zip cord*. That would make the expensive cable look bad. But the $ 1200 cable with slightly higher "preference" proves that expensive cables sound better, right..

 

*) By using stereophile's logic I conclude that $ 8000 cables make little to no difference to a $ 3 zip cord.

 

 

When John Atkinson is asked if he can hear a difference between cables he comes up with anecdotes of back-alley blind tests that he passed. If he has golden ears, why doesn't he do a properly documented and statistically significant blind test that proves that he really can hear differences? If his hearing is as magic as he says he has nothing to lose, only to gain. Why doesn't he accept the $ 1 million offer by James Randi that a $ 7250 speaker cable makes a difference?

Also see this.


Edited by xnor - 3/5/13 at 4:56am
post #1950 of 2869

Guys, I personally believe in cables, but not unobtanium ones that costs 8000$. For me that is more than absurd. 

However, I do believe in differences cables could bring to your system, bad or good. I have recently found out that even USB cables make a difference. Yeah...you heard me...usb cables. Bash me all you want, I do not care. All that I know is that I found a really cheap USB cable that really goes well with my system.

The usb cable costs 70$ or something like that. I gave it to a friend of mine who tested it along the stock, audioquest coffee (that has is 6x pricier) and wireworld starlight red (twice the cost). He liked my cable the most , even over the 6x times pricier AudioQuest coffee. He also did blind tests with them and concluded the same.

 

Before testing it and finding this, I thought usb cables were bs, but now I am sure that they can bring differences. However, I personally do not believe in very expensive cables. 

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