IM Distortion, Speakers and the Death of Science


One topic that often comes up is perception vs. measurements.

"If you can't measure it with common, existing measurements it isn't real."

This idea is and always will be flawed. Mind you, maybe what you perceive is not worth $1, but this is not how science works. I'm reminded of how many doctors and scientists fought against modernizing polio interventions, and how only recently did the treatment for stomach ulcers change radically due to the curiosity of a pair of forensic scientists.

Perception precedes measurement.  In between perception and measurement is (always) transference to visual data.  Lets take an example.

You are working on phone technology shortly after Bell invents the telephone. You hear one type of transducer sounds better than another.  Why is that?  Well, you have to figure out some way to see it (literally), via a scope, a charting pen, something that tells you in an objective way why they are different, that allows you to set a standard or goal and move towards it.

This person probably did not set out to measure all possible things. Maybe the first thing they decide to measure is distortion, or perhaps frequency response. After visualizing the raw data the scientist then has to decide what the units are, and how to express differences. Lets say it is distortion. In theory, there could have been a lot of different ways to measure distortion.  Such as Vrms - Vrms (expected) /Hz. Depending on the engineer's need at the time, that might have been a perfectly valid way to measure the output.

But here's the issue. This may work for this engineer solving this time, and we may even add it to the cannon of common measurements, but we are by no means done.

So, when exactly are we done?? At 1? 2? 5?  30?  The answer is we are not.  There are several common measurements for speakers for instance which I believe should be done more by reviewers:

- Compression
- Intermodulation ( IM ) Distortion
- Distortion

and yet, we do not. IM distortion is kind of interesting because I had heard about it before from M&K's literature, but it reappeared for me in the blog of Roger Russel ( http://www.roger-russell.com ) formerly from McIntosh. I can't find the blog post, but apparently they used IM distortion measurements to compare the audibility of woofer changes quite successfully.

Here's a great example of a new measurement being used and attributed to a sonic characteristic. Imagine the before and after.  Before using IM, maybe only distortion would have been used. They were of course measuring impedance and frequency response, and simple harmonic distortion, but Roger and his partner could hear something different not expressed in these measurements, so, they invent the use of it here. That invention is, in my mind, actual audio science.

The opposite of science would have been to say "frequency, impedance, and distortion" are the 3 characteristics which are audible, forever. Nelson pass working with the distortion profile, comparing the audible results and saying "this is an important feature" is also science. He's throwing out the normal distortion ratings and creating a whole new set of target behavior based on his experiments.  Given the market acceptance of his very expensive products I'd say he's been damn good at this.

What is my point to all of this?  Measurements in the consumer literature have become complacent. We've become far too willing to accept the limits of measurements from the 1980's and fail to develop new standard ways of testing. As a result of this we have devolved into camps who say that 1980's measures are all we need, those who eschew measurements and very little being done to show us new ways of looking at complex behaviors. Some areas where I believe measurements should be improved:

  • The effects of vibration on ss equipment
  • Capacitor technology
  • Interaction of linear amps with cables and speaker impedance.

We have become far too happy with this stale condition, and, for the consumers, science is dead.
erik_squires
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FYI, even at the cost of some of the high-end dCS stuffs, I believe their Sigma Delta Ring DAC technology only has 5 bits on the output, because anymore bits would overload the hardware to point of being impractical to implement on the hardware.

Yes, you read that correctly - only 5 bits.  That should wake up some people who think technology will replace human.
Until you extend your concept of what a "computer" is, you will maintain this simple and erroneous view of both what is possible with AI, and this view that the human mind is somehow "special". The human brain is just a biological implementation of what amounts to a computer, but if you have a hard concept of a computer only being digital logic then you will not understand where AI will go.
It's true that at least in theory, a human brain is made up of the same stuffs such as electrons, neutrons, protons ... just like a computer so in that sense a brain is not "special" nor does a brain is endowed with any "divine" properties.

But it's a stretch to say AI will replace human.  

In a given very specific task, an AI could replace a human, but in very limited and controlled environment.

For example, an AI can land a Boeing 747, but it could only be done in very limited and controlled situation.  When you add cross-wind, turbulence, and multitude of other external factors, no sane pilot will allow an AI to take over the airplane.  


It may be a bit slow in coming from me, but I want to clarify a bit of what I already posted a while back. I said:

’I don’t think it is so much the death of science that has stopped the adoption of better measurement methods so much as it has been the rise of marketing. Not just the sheer amounts of advertising, but journalism and also the advent of the internet of plenty have conspired to distract us (the consumers) from the notion or concept of what a relevant set of measurements might look like or the significance of its role.’

’Once that notion fell out of public consciousness, then the pressure was off of manufacturers or advertisers to maintain it.’

When I used the word ’conspired’, I did not actually mean to imply a ’grand conspiracy’ that is always to be considered automatically malevolent toward the consumer and that we are all somehow doomed. It was not my intent to project that as a determining attitude of mine or that it was sufficient grounds in my mind to never trust in manufacturers or in innovation ever again. I’m sure at the least I neglected to say that those things **inadvertently** conspired against us, on that point anyway. Even though I’ve had many occasions in my time to feel as though I couldn’t take manufacturers at their word, that was not my point. What I was trying to illustrate was the **mechanism** in the marketplace by which I believe the pre-existing public awareness of measurements and their role had left us. I know my remarks were seized upon earlier in the worst light (my own fault for not being more clear), but I’d prefer to take a moment and set that straight here. And if because of it I came across as unseemly toward manufacturers here, then I apologize. Anyone that I can believe is attempting to further the causes of both maker and end user alike is, contrary to how it may have looked, is quite welcome here by me.

I believe I welcome innovation as well as the next person. But then again, innovation in the market can be notoriously hard to spot. I’m still in the middle of reading the material...but white papers and I argue a lot...and I lose those arguments more often than not.

But, I remain fixed that my ears will have the final say, whatever the tech is or promises to be. Yet I look forward to progress. In the past, tech innovations have come from other disciplines or fields...like Bybee devices by way of the DOD. It does not surprise me to find this trend continuing, should it pan out.

But, as has already been pointed out, I’m sure Erik is dead on the money for raising the question from the start and I would love to see it answered positively, from whatever quarter that may come.