CD stoplight - some analysis

:SLEEP:

Usual wriggling and double standards from the Snake Oil Brigade.

In the big scheme of things I dont care either. If you want to spend your money please do. that isnt what we are discussing.

But the zealots are happy if we try to conduct a test as TONES suggested and ISSAC is doing, but will only accept the outcome if it fits there preconcieved ideas.

You obviously havent had a read any of Helmholtz. He clearly documents where people will say they hear something when it wasnt there especialy when it meets there own view of the world.. This has been known for about 150 years. Apart from the audio world of course.

This power of suggestion is used to great effect and profit by some very dubious members of the alternative medicine community... Come to think of it just the Audio World.

 

Robbo
I thought you were ignoring me after the last time I put you right on this subject about 2-3 months ago.

 

ok all you SONS (Snake Oil Nay Sayers)
if an experiment 'proves' that there is no significant difference in the 2 measured samples but someone prefers the sound of the snake oiled sample what does that prove? that the person has a mental disorder or that the experiment was measuring the wrong thing?
i don;t think robbo said he had golden ears, just that as he listens to his music a lot he tends to use his ears when choosing equipment.
i'm all for objective measurements, and i'd be extremely interested to see how isaacs experiments turn out. however i find carting 'sillyscopes and pc's loaded with sampling and fft software round to dealers whilst auditioning a little tedious so i tend to just listen to some favorite bits of music and choose the kit, that plays it to my liking. a compromise maybe but one that has garnered me a system that i enjoy every day.
just for the record i'd probably trust robbos ears more than anyone else's on the forum except maybe henryt's and WM's, he's pointed out problems in a number of peoples system such as phase anomolies and been right about them when they've been investigated.
cheers


julian

 

The experiment isn't measuring the wrong thing as all it's doing is measuring the output of the CDP, although as has been pointed out the analysis needs to be conducted carefully as transforming between time and frequency domains can be rather sensitive to exactly how you do it. If the experiment shows no significant difference you'd need to consider what kind of resolution the measurements have and how they compare with the resolving power of your average SOZ's ears But if it shows no difference then I'm afraid we're back to DBT as the last opportunity for the SOZ to demonstrate that the difference really does exist and isn't just down to his inherent unquestioning credulity... :MILD:

 

I have answered all the questions you have asked.

You keep trying to change the subject onto personal attacks.

I have not concluded or eluded to your statement

"If one follows their naive logic to it's conclusion, all CD players, speakers and amplifiers capable of performing in a linear fashion over the audible frequency range would in fact sound the same, CD would indeed give perfect sound for ever, and there would be no hifi industry outside of the major multinationals."

We are talking about the Green pen issue. Not amplifiers Cd players DACs or even bicycles chain oil.

You sir convieniently forget the past discussion we had a couple of month ago where I pointed you to a couple of places which backed up the concept of this being started as a joke.
I have also given you some info on how the laser pickup system works as I have been lucky enough to have worked with one of the original designers of the cd system, who worked for Phillips in the 70's

I have also worked on the development some DVD technology which you use today on the assumption you have a DVD player.

What I find so interesting is when someone with knowledge counters the "Snake Oil Brigade" the persoanl attacks start.

You are the sort of people who would argue with Louis Pasteur and tell him he knew nothing about pasteurisation.!

If I have now, or in the past made a technical error I would be more than happy if you corrected me.

Let us get back to the subject of this particular thread.

CD STOPLIGHT SOME ANALYSIS.

 

Merlin
Point taken, I missed that one.

Mind you I am not 100% sure what you are asking. I was talking about scientific analysis (the subject of this thread) and you brought up music is art.

Ultrasonics... no idea. I have never said I know anything about it
But I do know a LOT about CD/DVD laser pickup systems.

back to this one. My posts on HiFi choice have little or no relevance to the CD Stoplight analysis.

If you wish to pursue other areas then do it via another thread

 

Steady on chaps, Isaac started this thread with the interesting objective of testing the green pen, so no-one can complain that it's turned into a thread about measurement rather than subjective listening experience.

I'd be interested in seeing whether the experiment repeatedly produces similar results. It doesn't answer whether the green pen makes an audible difference, but it may answer whether it actually does anything at all, a very useful first step, and not the kind of test one usually reads about.

Surely, sometimes even dyed in the wool subjectivists want to find out if there's any plausible basis for their listening experiences?

-- Ian

 

I doubt it. That smacks far too much of commen sense.

 

ian,
even if there are objective reasons for the supposed effect of the green pen (see me sit on that fence) surely only subjective tests can ascertain whether it's going to be effective in an individuals particular circumstance. yes the output of the cd player is one thing but when you figure in everything that happens to that signal afterwards it seems like a bit of a pointless exercise especially when psycoaccoustics and the individuals brain and it's perception of the music is taken into account.
still it makes for a nice argument though doesn;t it...
cheers


julian

 

Absolutely. But isn't it interesting to see if, in fact, there is any kind of measurable effect? Kudos to Isaac (who believes the pen works) for starting to test that. Not much kudos to the people on this thread moaning about how only their ears matter and testing is irrelevant, they're missing the point quite spectacularly.

Frankly, the majority here are subjectivists (myself included). An occasional foray into testing whether measurable differences really exist is an entirely positive counterbalance.

-- Ian

 

ian,
i'd agree with you wholeheartedly that the results are interesting in a purely academic sense. my own personal feelings about the green pen is that for some cd's it works quite well, others it does nothing at all and still others it kills the dynamics. the only problem is that you don;t know what it;s going to do until you try it. i've tended to leave it alone as it's too unpredictable for me.

cheers


julian

 

Chaps,

All I can say about this thread is 'amazing' - absolutely amazing. It's interesting to see a few individuals get excited over graphs as proof that the green pen works when the only proof they really need is to use their ears in an unsighted test. Yet the same people who are getting excited and being congratulatory over these graphs are the same people who were pouring scorn on the blind test idea.

At the bakeoff at Julian's where people 'heard the change' with the green pen, according to Zanash above, was that test conducted blind? If not the results, just like the published graphs, are meaningless. This in my view could help explain why there is so much mediocre and poor-sounding equipment in today's high-end as designers have forgotten how to use their ears and rely just on computer graphs to determine how good a component sounds.

Anyway, as many of you seem to be turned on by the graphs, how about performing the tests with graphs in hand (just to keep the chartists happy) but in a manner that does not suggest to the listener that one of the discs has been marked with a green pen. In other words 'blind'. Has such a test been performed by the bake-off enthusiasts? I wonder how the results of that test would correlate to the results of the graphs? I have to say though that the mind really does boggle sometimes especially when reading the posts of many ZeroGainers and whilst on the subject of graphs, I'm now off to plot a few for a client but I can assure you it's nothing to do with audio.



Enjoy the music,

Lawrie.

 

Lawrie,

I dont see anyone taking these graphs as proof. In fact pretty much everyone is being very cautious of the results and would like to see further tests done to remove the experimental error and show that the measurements are genuine.

In any case, even if the measurements do show up differences, they still arent necessarily the things that people are hearing between treated/untreated discs. However I suppose that being able to measure some changes between the discs is something.

btw, you do seem to have a kind of fascination for these get togethers some of the forumites have from time to time. Whats the deal?

 

Ian,

my point is that the graphs are sadly meaningless in reality. If Isaac wants to conduct the "experiment then fine.

Personally I'd rather listren to music. My point is that recently everything on this forum seems to need a scientific explanation, when the science employed is itself flawed.

I've nothing against blind testing per se, , but to insisit it is the only way to determine whether to buy something is plainly missing the point of the majority of listeners. It all depends on your reason for buying something surely.

If I'm missing the point then I apologise. What is it by the way?

 

If the graphs repeatedly showed treated and untreated CDs played absolutely identically, then it would prove unambiguously that subjective experiences to the contrary were psychoacoustic. There would be no other explanation, regardless of what one's ears told one (this is not absolutism, just the fact that if there is no difference in the audible output between the treated and untreated discs, then they must, by definition, sound the same). If, OTOH, repeated tests show consistent variation, it would suggest that there could indeed be an audible difference (although it wouldn't prove it, that would take a blind test). It's the difference between knowing one is deluding oneself and knowing that one may, in fact, not be deluding oneself at all.

The listen to music thing is an irrelevance. This is a thread about measurement, not about listening. There are plenty of other threads about listening experiences, almost none where somebody actually tries to test something.

We've had this thread, the DBT thread, the CD transports thread, and the Demagic thread recently where these issues have been discussed. The overwhelming majority of regular posters here believe that cables, supports, mains treatments, green pens, and the like, make a difference. In other words, the recent threads are the exception rather than the rule. I think they make a refreshing change from the usual "mains cable x adds lots of thwack" type discussions that happen here endlessly.

Nobody, apart from Lawrie, has actually suggested that. Not even dat19.

-- Ian

 

Mike,

Would you care to say how the science is flawed, or are you just rabble-rousing? (And again on BT - not that this is what this thread is about - not many would say it's the only way to buy kit, but it's the only way to buy kit based on only "using your ears")

The point, as I see it, is to demonstrate the the gree pen actually does make a difference to what the CDP produces, as opposed to just our perception of a difference. I'm fully will Ian on this - Kudos to Isaac for actually doing something and big rasberries to all the head-in the sand SOZs. I really can't see why stebbo gets such a hard time for asking perfectly reasonable questions (Merlin is clearly just in rabble-rouse mood - again - but for Robbo to join there as well is quite inexplicable for a professed scientist and aparrently intelligent man).

I have a green pen, have used it, have believed it to make a difference in certain cases, but wouldn't bet my life, or next pay packet, on it - and certainly couldn't discount it as a purely psychological effect. I guess I would call myself an objective empiricist: if something can be clearly demonstrated to exist despite theory, then it does, and theory needs developing to explain it, but that demonstration needs to be made - and in this case the jury is very much still out for me.

The initial result is interesting, but any paper based on a single such result would eventually be laughed out of court (anyone remember "cold fusion"). I hope Isaac can do some more experiments to establish the level of experimental error. It would seem that some optimisation in the experiment could be achieved: the most obvious being that the major difference seems to come about 3 seconds in, so concentrating on that area may save some real-time, and a lot of disc-space.

 

And the second run (same order):





Again, differences exist between the two. However, both are different to the previous iterations, despite maintaining the same settings. This then suggests that experimental error is greater than any differences observed, although there does appear to be one consistent difference (the size of one peak is consistently larger in the top graph of the two), but the data set remains too small to draw conclusions on that.

Obviously a better test setup will help matters (and if i get access to an audio precision and some spare time, I might give it a go. Also, I might try some other analysis utilities on the data that I have collected.

 

OK, all you greenies, even though my view of the green pen matches Henry Ford's view of history, I must have a go. I have found a sacrificial CD (a Harmonia Mundi sampler disc of recordings of Philippe Herreweghe) and I need a green pen, which I shall acquire in Zürich tomorrow night on my way home (provided I can avoid Musik Hug and the CD sale). What kind of green pen am I looking for? Presumably mid-dark green? Presumably any sort of marker that will leave a uniform film on a plastic surface, no matter whether solvent- or water-based?

 

Tones, should you hear a difference, please ease us in gradually with your news - the shock may be too much for many otherwise I suspect

 

Tones- the proper stoplight pen is an opaque green acrylic paint which has a high level of absorbtion at the wavelength of the CD laser (infrared). The colour green is inconsequential, as long as the absorbtion at the laser wavelength is high. The easiest way to ensure that is to buy the actual audioprism pen, but I'm sure that there are plenty of other paints with the appropriate properties.