If it was easy everybody could do it. - Old audiophile axiom
An ordinary man has no means of deliverance. - Another old audiophile axiom
An ordinary man has no means of deliverance. - Another old audiophile axiom
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:
We have become far too happy with this stale condition, and, for the consumers, science is dead.
"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.
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- 335 posts total
What does "death of science" mean here? Here I take science to mean science in the public realm, as opposed to academic or manufacturer’s research. Because science involves progress and invention, so long as the educated public is stuck with a handful of metrics set in stone by the 1980’s that we discuss, I say that this science is dead. It has not progressed much at all. It had a fruitful life from the invention of the telephone up until the 1980’s and then died quietly. I think the general consensus here is (& @erik_squires certainly makes the case): we measure irrelevant things. Oh, no, not saying that. I’m saying what we measure is not enough, but we take it to mean all that is knowable. Imagine measuring the earth by it’s diameter and mass and saying that’s all we must know about it, and that tells us everything we need to know about the earth. Well, if your sole interest is gravitational, momentum and orbit, then yes, I supposed that’s true, but these two metrics ignore:
I’m not saying the earth’s diameter and mass are irrelevant, far from it, but I do think we are stuck somewhere far from knowing everything about say, capacitors or amplifier/speaker interaction. We just accept that publishers publish mass and diameter and that science is done and then must leave the rest to popular opinion, social media and taste makers. I disagree. |
Very interesting and thought provoking thread thus far. I believe I’m highly capable of stopping this intellectual, educational and inspirational audio forum brainstorming session juggernaut dead in its tracks with my highly suspect thread contributions. If you all refrain from doubting my capacity to do this, I guess I can refrain from intentionally deploying my vast capacities to train wreck this excellence. I agree with the premise that past and current objective speaker standard measurements poorly correlate with the subjective individual perceptions of the sound qualities of specific speakers. At best these standard measurements, such as impedance and efficiency rating, are most useful in determining the viable amps to drive them with. Perhaps speaker type is the best current indicator of subjective sound qualities perceived. From my perspective, the biggest hindrance to creating a high quality and enjoyable home audio system is the complexity involved due to the high number of components, the high number of available options for each system component and the variability of how well specific system component parts perform with other specific system component parts. This results in an extremely high number of possible unique system combinations or permutations that requires knowledge and experience to simplify. Personally, it took me decades of knowledge building, experimenting and accumulated experience to assemble a high quality audio system that I deeply enjoyed. Slow learner you say? Perhaps, but I think it may seem like an especially daunting venture, or more appropriately an adventure, to assemble an enjoyable audio system to the newcomers to our hobby. I believe improved objective measurements of audio gear, that incorporate the knowledge gained from the field of psycho-acoustics, and are somehow more closely correlated with subjective listening would likely be difficult but also very useful. Tim |
the high number of available options for each system component and the variability of how well specific system component parts perform with other specific system component parts.This is very important for sure.... But after you have linked compatible components, the most important factors are their embeddings in 4 dimensions: mechanical resonance-vibrations grid, electrical grid of the house not only of the system or of the room, the passive treatment of the acoustical space, and after that an active treatment of the acoustical space.... Measuring is an active temporal evolutive process, be it at his best for speakers for example, it cannot replace the 4 embeddings to guarantee a good S.Q. ….My opinion is we need feed-back measuring process not only in a designer shop but also in our room with our particular embeddings methods and particular electronic components...With the progress of science this is already there, if not this will be possible tomorrow... |
- 335 posts total