This is a bit off topic but I didn't want to start a new thread. We've discussed binaural recordings here, and the crosstalk-cancellation needed to play them properly over speakers.
There are a number of commercial DSP units that do that to various success, but are generally very expensive. The only software that I've found is this, and it's not free: http://www.wavearts.com/WaveSurroundPro.html
The method is described in Gardner's thesis, along with making binaural signals from non-binaural ones. http://sound.media.mit.edu/Papers/gardner_thesis.pdf
Detailed HRTF measurements are available freely, so I don't know why I can't find any free software that will do this. It would be great to find a tool that would convolve a music file with the appropriate filters, so I could rip, process, and burn all my CDs for a better speaker listening experience.
Of course, I could just put a physical barrier between the speakers, but people would laugh when they see it.
Well duh, that's by definition. That's why religion is bull****, because it's unfalsifiable.
You're approaching religion from the wrong angle... you're getting caught up in the doctrines of religion, and missing out on what I believe to be true religion, which is a relationship with God. If you were to ask God to reveal Himself to you, and then spend a week or so keeping that question before Him and giving Him a chance to show Himself to you, I'm convinced that at the end of that week you'd have a different opinion of what true religion is.
Tonight I breadboarded my first "serious" headphone amp, measured it & did some listening. OK, but not spectacular on the subjective, into the limits of the measuring instruments on the objective. My full-sized system beats this initial amp w/Senn 600s readily. Obviously, there is much more to do on the amp, but I knew that before power-up. (Hmmm - is that why I'm not dazzled?)
Much of what we hear can be measured, with the right techniques, of which 1930s THD is just one of an arsenal of methods needed (some of which haven't been discovered yet). Years ago, I found that perception of distortion is much more sensitive to IMD than THD. Ordinary amplitude clipping produces much more IM than HD in complex-waveform simulations. Yet so many measurement-oriented folks remain fixated on THD (this is less so in Europe). And the vast majority of published data involves THD or 2-tone IMD, nothing more complex.
This gets more interesting when feedback is considered. When I listened to a bandwidth-limited, measureable delay, low-distortion amp with and without FB, the FB worsened the sound. The FB was obviously trying to correct a condition that had already passed and, therefore, adding a stale corrective factor into a later input signal. Does this mean that FB is always bad? Or that this particular set of propagation delays and bandwidth limitations just wasn't compatible with the particular FB used?
Phase distortion and phase modulation in particular aren't considered in traditional audio measurements, yet we know they're audible.
The popular steady-state tests reveal few of these phenomena, as feedback aligns itself to correct the signal within the time frame of the measurement process. Could other, transient-oriented tests reveal them? Maybe not all phenomena, but certainly more than what we obtain from the traditional methods.
So, where are the techniques, and why haven't they been developed? First, they don't illustrate theoretical principles being taught at the undergraduate level, so there's little market in the university laboratory environment for test equipment & techniques that don't compliment the traditional educational sequence. Second, some of the folks with the best potential ability to develop correlational techniques simply reject objective measurements out-of-hand. If half the effort expended in arguing the merits of subjective vs. objective went into the development of better-correlated measurement techniques, objective measurement and subjective result would both take a leap forward, I would think.
We have computational and simulation tools available now that were unimaginable when I was an undergraduate 30 years ago. Hopefully, some bright young minds will step outside the box and develop DSP applications that reveal more of the anomalies we hear, thereby providing the means for more rapid sonic improvement of products.
Appropriate measurements help us understand what we hear. Improving measured results is a tool that's often helpful along the road to better sound. But the goal cannot be solely the measured data, as that's not what satisfies the customer in the end. That doesn't invalidate the usefulness of measurement, it merely establishes some limits on it.
The measurement techniques I have available on my bench won't, by themselves, help me improve my amp's initial sound. Steady-state tests won't reveal a dynamic regulation issue in a power supply, for example. But they'll come in handy every now and then during the evolution of this project, which I will know is complete when it matches or beats the sound of my full-sized system.
When I listened to a bandwidth-limited, measureable delay, low-distortion amp with and without FB, the FB worsened the sound. The FB was obviously trying to correct a condition that had already passed and, therefore, adding a stale corrective factor into a later input signal.
Right, first up I guess I should say "Hello" to all. First post here and all that. Getting close to a lot of areas I am very interested in.
So, to weigh in:
I'm curious how you did this evaluation. Listening to a given amp in both open loop and closed loop is not going to be at all easy. What was the open loop gain? One assumes it must have been reasonably low, or you could not have done the test. So what was the feedback ratio? At what frequency is this?
Secondly, the idea that the amp was "trying to add a stale factor" really won't fly. I have no doubt that they sounded different, and your preference, but the rationale for the difference is very hard to believe. This goes to the root of how a feedback amplifier works. Yes there is a delay, and yes it is important. Indeed it is pretty much covered in the Nyquist stability criterion.
There could be a huge number of reasons why an amplifier could sound worse when the feedback loop was closed. If it had been designed to work open loop I would have grave misgivings that it would also operate correctly with the loop closed. It might operate OK, and indeed generally seem to be working, but immune to some of the well known failures of feedback design, that is harder to judge.
I have never heard anyone define philosophy the way you did. It is not the job of the philosopher to postulate scientific theories, it is the job of the scientists to both do that and test them -- thus the distinction between theoretical and experimental scientists in some theories (especially physics). Physics theories are generally born in the minds of theoretical physicists, not philosophers. In regards to science, philosophy concerns itself with metaphysics, ontologies, etc., defining what science is, how its methods can be rationally justified, and just what scientific results actually mean. Doing the science is left to the scientists.
That's pretty recent. It's only been the case from the start of the 20th century. Keep in mind that Enrico Fermi was a great theoretician and experimentalist. The big reason for the dichotomy nowadays seems to be that the mathematical sophistication required for most "research grade" theoretical physics precludes one from being at the forefront in both "fields". As far as I know, one of the prerequisites for being a good experimentalist is understanding the underlying theory. And I mean they have to really understand it well enough to know exactly what they're doing, and not hackishly applying equations for no apparent reason, I mean, that's what engineers are for, right * You'll note that such a dichotomy does not exist in the other sciences (I'm not counting "theoretical" chemists here, since they're basically molecular physicists in the Chemistry building).
Addressing the Philosophy issue, I've heard from some fellows (odd ones, but respected nonetheless) that philosophy will have increasing importance in Physics as we move along into this new century (which, unfortunately for me, looks to be the century of Biology). Here at the University of Washington, we've got a Professor of Philosophy that's adjunct in Physics. He's even got several PRLs under his belt, so one assumes that he knows his stuff. I'm not going to defend it any further than to say that philosophy did, at one point in time, have a place in Physics. To say that it never will again, is ... well, bold, I think. Don't get me wrong, I like to mock philosophers as much as the next guy (one recalls the Sokal hoax with fond memories), but I think that to seriously write them off wholesale is a bit much.
As for the topic of the thread, I believe very strongly in blind tests. I have such faith in them that I further believe they represent the only true data (though perhaps it's going a bit far...). Sure, they have to be conducted right, but to discard them as useful tools simply because they usually aren't conducted right is foolhardy. A dearth of good data is merely evidence that someone needs to take good data. The fact that the people with the most interest in this field, with the greatest resources for accomplishing these tasks have not even attempted them implies to me that the effects in question must not exist. It is simply a matter of money and desire, and don't tell me that magazines like Stereophile lack the funds. As for desire, I would expect anyone with a finite budget to find this information at the heart of the matter.
Now ... as for Mr. Atkinson
Quote:
Originally Posted by John Atkinson
[...]This collection a) proves that, of all scientists, theoretical physicists seem to have their feet most firmly on the bedrock of reality,[...]
I hate you. To pick arguably the most beloved of all physicists and apply him as a general model for all theoretical physicists (and modern ones at that!) is utter blasphemy. There is a very severe gap between the theorists of yore and those we are stuck with today (though the size of this gap, strongly depends on the particular subfield...). I have heard that Russian string theorists call themselves mathematicians and eshew the title "physicist" because they don't think that what they're doing is, strictly speaking, physics yet. Let us not forgot that the final arbiter of what is real and what is fantasy is the experimental result. Even Einstein knew this.
* For those that do not see that I am joking here, I am applying the standard engineer stereotype, as seen by physicists. I mean no harm, just thought I'd throw it in for kicks.
Well, it's not really a dichotomy because there are in-betweens. This is just division of labor, of course. Since Newton's time, the sciences have become too much for one person to know fully in detail, thus the increasing number of specializations. It's been a while since I posted that, but I think my point was that whatever was originally the case, natural philosophy is no longer a branch of philosophy (and that's why we don't call it that anymore, instead referring to it as science). I see an enormous separation between philosophy and science today.
This might seem like a ridiculous suggestion, but is there really any reason you couldn't just make two cheap amps (cmoy equivalent), mark them internally, power them w/ the same power supply, use two different chips and weld em shut? Just ship them around to the head-fi members and gather data. When you are done testing just cut the amps open and see which one got picked more often or if it was 50/50.
It's not that simple (as you have guessed). Proper blind testing is a wide subject in the field of psychology and experimental science, and audio presents its own complications. But this has already been discussed to death at the AudioAsylum and DIYaudio forums. What's the most potentially constructive area to research is finding measurements and metrics that correlate best with perception, so that the complexity and carefully controlled environments of blind testing can be avoided. The various papers quoted in this thread show that over the past decade this has begun picking up steam, but lots more is needed.
It's not that simple (as you have guessed). What's the most potentially constructive area to research is finding measurements and metrics that correlate best with perception, so that the complexity and carefully controlled environments of blind testing can be avoided.
Those tests won't tell you why individuals have different preferences, if not perceptions.
__________________
There are 10 kind of people in the world - those who understand binary and those who don't. ShinyMetal Site| RSS |Forum
d(-_-)b | [:] :)
* You'll note that such a dichotomy does not exist in the other sciences (I'm not counting "theoretical" chemists here, since they're basically molecular physicists in the Chemistry building).
Linear Mode
