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
It is the human ears that judge the superiority of any electronic component, not in the abstract, disembodied standardized field of measurement necessary for implementation of the engineering protocols, but in the embodied particular multiple embeddings of your room and house and in a particular individualized audio system....

Then the most important underestimated facts in audio are the controls of the 4 basic embeddings : mechanical, electrical, and the passive and active controls of the acoustical field of the room ... There are others dimensions but these 4 one are fundamentals...


Buying first a high quality design electronic component is very important, but the evolution of the design of electronic component in the last 50 years, as big as it is, is not on par, nor on the same scale, than the difference in S.Q. gained by a rightful implementation of controls protocols for the 4 embeddings...

This is my audiophile journey lesson...Nobody explain me that clearly, I discover it myself by listening experiments, slowly first in the first 5 years, and swiftly in the last 2 years...


Improving electronic design is very important, but learning to listen and resolving in a simple and affordable manner the 4 embeddings problems are the crux of audio and the more fundamental problem...


Most of us we owns already a good audio system, the real question is not about the way to upgrade the design of an electronic component by buying a new improved one; the real question is : Do I know from having heard it already, how my audio system, as it is now, behaves in an optimal controlled environment ?


The answer for most people will be no....Frustrated by the limitations of their actual system, without knowing that the limitations comes from the lack of control of the embeddings, more than from the already good design of their actual system " per se", they turn themselves prey to marketing ploy and upgrade, without even having heard their system in his optimal possibilities to begins with...


This is what I learned ...

Note:
I am not a closed mind, and I am conscious of the importance of improved engineering methods and products...

I looked about that suggested here and it seems interesting : the GedLee Metric..

I am interested for sure also in new design, for example ZOTL technology...
@alymere
The science is not dead; it’s getting more and more interesting.
I agree. 
I think the general consensus here is (& @erik_squires certainly makes the case): we measure irrelevant things.
So, it's not science but how it is applied to audio that is (mostly) dead (of meaning).
Mostly... 

(BTW, speaker response measurements, can be very useful; MLSSA & FFT are very useful tools. )