Of course, if you're comparing two power amps with identical or nearly identical frequency responses into the speaker, that "positive control" is entirely inappropriate- it's not the phenomenon you're trying to detect. Problem is, there's no reliable DBT data showing that, for boxes of gain, anything other than frequency response (assuming no clipping) and level are audible (noting, of course, that people show fabulous sensitivity to those things), absent gross distortion or grossly poor crosstalk, which are highly unlikely in modern amps, other than certain insanely expensive tube amps.
So what you're proposing would seem to be impossible. Circular reasoning seems to be a theme here...
So what you're proposing would seem to be impossible. Circular reasoning seems to be a theme here...
At the speaker terminals; same with level adjustment. Just about any amp is flat into a resistor, but if the source impedance is high, it won't be into a speaker load. For the case of a line amp (which is what I thought we were talking about), at the power amp input- but I haven't seen a non-flat one in decades, it's trivially easy to do.
I did understand, but the same holds for an open test - I think it's perfectly feasible to properly (or at least try to) take into account the influence of room, speakers etc. both in an open test and in a blind one - merely blinding a test should't affect room response... The DTBs described in Nouisane's paper were designed to allow testers to conduct the tests in their own listening room, using their own systems, leaving them enough time to familiarize with AB/X system and to prove they were able to hear their own gear with the test stuff in place; the influence of the switchbox was evaluated, and found to be transparent, and listening level and freq response were checked/equalized before the tests.
I know that devil's in the details, but it seems nothing was taken for granted...
Yet, there's one thing that makes me a little bit dubious about DBTs outcomes, and it has to do exactly with what has been pointed out by Richard: it seems that when our brain knows what to listen to, then you actually hear it. So, when testing two grossly different systems, it may happen that after the very first switchings the best system instructs our brain to fill the gaps of the worst one in a way that you end up with two indistinguishable systems, even if they are very different... SY, what about this possibility?
L.
Well, you have to explain why that doesn't happen for frequency response, level, data compression, phase, and other phenomena that are routinely detected in a DBT. Also, why that doesn't happen for other sensory DBTs (e.g., organoleptic, haptic).
1. I didn't say I don't hear differences in blind test – I do hear differences, at least in some of them.
2. I didn't say that if I don't hear differences, the test must be faulty.
What I said is that in order for such a test to be valid, first it have to show that it can produce also positive results.
Depends on the phenomenon. Some things (e.g., absolute polarity) were more detectable on special test signals. Other things (e.g., level) were easier to detect with music. You might consider actually reading the literature.
Hi Joshua:
Assume we would both agree to DBT the following statement:
"Joshua can hear differences between A and B", where A and B are, for example, two power cords.
What would be an example of "positive results", as you mentioned above?
What is not obvious is that our “hearing” is an adapted skill which because it is learned, also includes what you already know and even less obviously includes what you see. In hearing acuity tests, the object is to evaluate your hearing alone and so there are NO visual clues and an effort made to exclude any external sounds.
A fun demonstration of that “invisible to us” link between what we see and “hear” is the McGurke effect.
Try this and ponder why we only hear sonic reality when we don’t see anything related to the source AND how a blind test (conducted w/o visual stimulus like a hearing acuity test) can give a very different impression of “hearing” than a sighted one.
Try The McGurk Effect! - Horizon: Is Seeing Believing? - BBC Two - YouTube
Best,
Tom Danley
Danley Sound Labs
A fun demonstration of that “invisible to us” link between what we see and “hear” is the McGurke effect.
Try this and ponder why we only hear sonic reality when we don’t see anything related to the source AND how a blind test (conducted w/o visual stimulus like a hearing acuity test) can give a very different impression of “hearing” than a sighted one.
Try The McGurk Effect! - Horizon: Is Seeing Believing? - BBC Two - YouTube
Best,
Tom Danley
Danley Sound Labs
Well, you have some experience with DBTs.
The issue with output impedance is avoiding the unintended effects on level and frequency response (I know you know that, I'm jes' sayin' for completeness).
No explanation at all
- was only speculating on my experience when switching between CD and SACD versions of the same program; it sometimes happened that after discovering in the SACD some details I had never heard before, I noticed I was able to hear the very same details when reverting back to the CD version. Bias power...?L.
Huh? It will what? I asked for an example of "positive result" in this particular DBT.
@ zinsula,
thanks for the reminder.
@ SY,
Seems that requesting some data to back up your assertions beats something to death, mhm?
Could you please present an argument containing some statistics (or data) to shed a light on this?
Which obvious statistical result was ignored by me?
What was the "post hoc reframing" in the Fremer case??
Do you have any evidence that the results were "poorly controlled" in the Fremer DBT at the AES-Convention?
It is my experience that people indeed can hear such things if the tests don´t include additional confounders they are not used to.
And yes (that is pretty basic stuff in psychology/sensory testing as well) a controlled listening experiment is a confounder by itself.
I´ve cited ITU-R BS.1116 and the other recommendations for subjective evaluation quite often; please reread the parts which describe the efforts to let the (even the expert panel) listeners accustom to the materials and test protocols.
If bringing scientific requirements back to memory is "to kick up unrelated dust to confuse ...." i am guilty.
thanks for the reminder.
@ SY,
Seems that requesting some data to back up your assertions beats something to death, mhm?
Could you please present an argument containing some statistics (or data) to shed a light on this?
Which obvious statistical result was ignored by me?
What was the "post hoc reframing" in the Fremer case??
Do you have any evidence that the results were "poorly controlled" in the Fremer DBT at the AES-Convention?
It is my experience that people indeed can hear such things if the tests don´t include additional confounders they are not used to.
And yes (that is pretty basic stuff in psychology/sensory testing as well) a controlled listening experiment is a confounder by itself.
I´ve cited ITU-R BS.1116 and the other recommendations for subjective evaluation quite often; please reread the parts which describe the efforts to let the (even the expert panel) listeners accustom to the materials and test protocols.
If bringing scientific requirements back to memory is "to kick up unrelated dust to confuse ...." i am guilty.
No problem at all; zinsulas proposal is reasonable- a positive control is an effect that must be detected under test conditions and of course it should be comparable up to a certain degree.
If the experimenter doesn´t really know what to search for that presents a difficulty, but it is no excuse for violating the scientific rules.
An experimenter has to show that the experiment is objective, valid and reliable.
Of course.
Who says it does not happen??
In fact it does happen all the time in controlled listening experiments; please reread the documentation of public tests with quite big sample sizes, for example the stereophile test on amplifiers.
When in a certain blind test I hear differences between say power cables, that certain test is capable of giving positive results. Else, I don't understand your question.
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