Placebo effect or burn in real?

[rodbac]

*disregard- more time today for arguing*

 

[Reputator]

actually I'd rather not get carried away. My last argument said all that needs to be said.

 

[Hirsch]

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Originally Posted by rodbac That you completely misunderstand both the placebo effect and everything said so far is now noted.

"Placebo" is a subset of what can be called expectancy effects, or whatever you want, but in reality the more we learn the less we know. Essentially, in the medical sciences, a placebo is a treatment with no (known) therapeutic activity. In order for a treatment to be considered efficacious, a group receiving the treatment must have a better therapeutic outcome than a group receiving the placebo.

Mechanisms of these effects are not known. I've been to at least one seminar focussing on placebo effects in pharmacology, in which the presenter demonstrated that, at least with certain classes of compounds, the presence or absence of a placebo effect could be predicted by genotype. This has nothing to do with any psychological phenomenon at all. Some people were genetically predisposed to placebo effects in these trials, and others were not. Got the genes, get the effect. No genes, no placebo effect. Nothing to do with psychology at all (note: study of placebo effects themselves is actually very rare in pharmacology, since it involves some very tricky ethical issues).

Somebody doesn't understand the placebo effect, and it does not appear to be the people you are replying to.

I've discussed methodological issues involved in measuring perceptual differences in the audio domain many times previously, and don't really feel like repeating myself here.

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Incorrect. They're very tiny speakers that don't go through the same excursion (even relative to their size) as larger ones. They're not meant to move air.

Priceless. At least you won't have to worry about listening too loud with a driver that cannot move air.

 

[rodbac]

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Priceless. At least you won't have to worry about listening too loud with a driver that cannot move air.

LOL- ok, Mr. Literal- they're not meant to move air in any appreciable amount.

Better?

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Mechanisms of these effects are not known.

No problem, since they're irrelevant to this discussion.

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Somebody doesn't understand the placebo effect, and it does not appear to be the people you are replying to.

If there's anything I've said that indicates I don't fully understand the subject, quote it and I'll explain it for you. That, or you'll just have to trust me on this one, chief.

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I've discussed methodological issues involved in measuring perceptual differences in the audio domain many times previously, and don't really feel like repeating myself here.

Uh, noone is interested in measuring perceptual differences- just in seeing if you can really tell a difference between two phones.

That those trying to support "burn in" invariably retreat to "it's just too complicated!" is telling.

It's not complicated- either you can discern between the two phones or you can't. Quit wasting your breath hollering to everyone how dumb they are for not believing and just show us you can do it.

 

[sethsez]

Although I agree that "placebo" is not being used to its correct dictionary definition, it seems a rather odd nit to pick on a board that frequently describes sound in terms of taste, visuals, feel... basically everything except sound.

If we can collectively understand what someone means when they describe a headphone's sound as "rich and warm" then can we move beyond the semantic bickering or at least pick another term and be done with it? Debating the true medical definition of placebo is an interesting diversion, but it's a diversion nonetheless.

 

[Hirsch]

Quote:

Originally Posted by rodbac Uh, noone is interested in measuring perceptual differences- just in seeing if you can really tell a difference between two phones.

I can tell the difference between a K-1000 and an R10 100% of the time, blindfolded and volume matched.

Oh yeah, you're talking about burn-in, presumably in the same model. Jazz has already demonstrated the physical effects of burn-in, so all that's left is whether that matters audibly. In that case you'd want to know whether or not they sound different. Here's a clue: hearing is a perceptual process, and determing whether or not you can tell the difference between two headphones is measuring a perceptual difference.

Amazing. You've managed to contradict yourself in a single sentence. I'm out of here.

 

[rodbac]

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Here's a clue: hearing is a perceptual process, and determing whether or not you can tell the difference between two headphones is measuring a perceptual difference.

Again, Mr. Literal- quit trying to cloud the issue by trying to paint it as some complicated measurement. Measurement implies quantifying, and we're simply looking for a yes or a no (correctly identified or not).

Either you can tell the difference or you can't. Simple.

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I can tell the difference between a K-1000 and an R10 100% of the time, blindfolded and volume matched.

Bravo.

 

[JaZZ]

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Originally Posted by rodbac Magnificent! Thanks for your hard work. Now please link us to those results.

Those results are all in my head and have not been brought to paper at any moment. I've given up speaker building long ago -- actually since my tinnitus has occurred.

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Also, I'm sure you'll have no problem blindly picking out the "broken in" tweeter in a test, right?

Not necessarily. In fact I've never experienced audible break-in effects with new speakers, for several reasons: The used chassis have all been mechanically broken in in advance, moreover I've always been busy with so many crossover modifications right after finishing of the prototypes that it was impossible to discern break-in effects from tuning effects.

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You're the perfect subject to finally lay this to rest.

Actually I thought so, since I've provided the forum with hard data about dynamic drivers changing their acoustic properties over time, especially when new and unused. But I see: For someone with the strong will to defend the opposite standpoint for some reason, it will never be enough.

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Whether you're speaking of it or not, that's all your tests point to - that it's not impossible.

Certainly. But more than this: it gives the physical break-in scenario a certain likelihood far above the one you're ready to concede (you still seem to think it's extremely unlikely despite the hard facts and all the manufacturer statements).

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And no, the excursions are not identical relative to the size of the diaphragms. That's the same nonsense brought up previously. In a 6" woofer, the excursion is visible and dramatic. In a 2" headphone driver, you'll hardly be able to see it vibrate. A speaker needs to move air, not just produce the frequency.

I think you're wrong. With my normal speaker listening level, I barely see the woofer membrane moving, just with very low frequencies and pulses. The same applies to headphones, once you've removed the protective foam or whatever to make the membrane movement visible. Of course the travel isn't as large as with a typical woofer, but every bit as large if you take the membrane size into account. -- Moreover, the primary task of every headphone membrane is to move air, which on its part finally makes the eardrum vibrate. Open(-baffle) designs such as HD 600/650 or K 701 have to do even larger excursions than closed(-baffle) designs, since with the former the sound waves aren't forced into the ear canal (as it's the case with the latter design), but can escape through the open baffle, additionally there's a certain degree of phase cancellation between front and rear of the membrane.

Actually exactly (proportional) speaker-like excursion doesn't even matter. If you think about it: with modern hard-cone speaker chassis the suspension (spider and particularly membrane suspension) is the main source of harmonic distortion. It's in fact the only vibrating parts that doesn't move like a piston. Their goal is to center the voice coil in the magnetic air gap, to prevent staggering and to limit the excursion -- the lower the frequency, the more this property takes effect. Especially the membrane suspension has a hard job: It has to withstand the out-of-phase pressure changes and at the same time to allow a homogeneous movement by means of a continuous compliance curve.

When new, the suspension is relatively stiff and brittle. That's why the compliance curve is most likely a bit jagged. With enough movement, the suspension gets more elastic, and its compliance curve gets smoother (and maybe also circumferal inhomogeneities get smoothed out) -- which leads to reduced harmonic distortion. That's the most likely scenario, as I see it. Now take into account that headphone membranes are usually partial vibrators, so a major part of them can be seen as a large suspension. Now you can draw your own conclusion...
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[rodbac]

Good reply, jazz, and you may be right.

I'll let everyone know when I have the time to come to Seattle or Portland for a little Head-Fi meet with a couple pairs of K701s or something- should be pretty easy to set up.

I'll get three or four pairs from Headroom, burn one in for however long and in whatever manner you all would like, and we'll meet and see who can hear the difference.

 

[spinali]

This was starting to get terribly interesting when things just, like, stopped. Did any results come from the tests? Don't tease us - it's just not fair.

 

[regal]

Why not just measure the T/S parameters of a headphone driver new 10 times vs 1000 hrs 10 times? Then do a T-test to determine if there is a statistical significant difference between the measurements.

Being an engineer I have the software to run the t-test. I don't have the equipment to test the T/S but surely some speaker builder here does. You would have to place the mike on one of those micrometer stands so you stay at the exact distance. Each time you measure (all 20 times) you would have to reinstall the mike and set the distance so you have the same variation between each measurement.

Sometimes a little science is the best answer to debates like this.

 

[akg_man701]

Wow - after reading all of that I almost forgot about the music.