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Measurements can tell secrets if you speak the language

Hi
At best, to someone who has a background of comparing measurements to sound qualities, measurements may be useful in describing what a given thing will sound like.
For the average person, measurements tell about as much as a string of numbers describing the lenses in glasses or Telescope.
Where measurements are critical is in the design and development of things, let’s say you were grinding a telescope lenses, where do you start?.
If you were limited to holding it up and looking at the trees etc outside (as they were initially), you’re not going to get very far in its development. On the other hand if one used some simple and known “test signals”, one can go a great deal further.
For example, by using a perfect circle drawn on the wall and by comparing the image produced, one can see astigmatic distortion is the image is elliptical instead of round. One can then grind the lenses to reduce the astigmatism.
One can put a perfect square on the wall and see if the image has trapezoidal or cylindrical distortion.
One could place a white paper on the wall and then compare the “whiteness” and “brightness” of the image produced to the original to evaluate different blends of glass etc.
One can put a dot on the wall and see how well the lenses focuses to a point and how deep the range of focus is.
For the guy grinding the lenses, saying it has such and such problem in its measurements MAY in fact tell that guy something about what the image will look like but is nearly meaning less to the person who will gaze at the stars and nature through it.
So, to the person developing something new, measurements are both irreplaceable and indispensable beyond some point. For the person buying the Telescope, measurements are numbers, they do not define how much the person enjoys the view or what they might see.
AS with optic’s audio measurements tell something but only about that particular condition. When an observed “audible” flaw doesn’t show up in a measurement, one is not measuring the source in the right domain. I suppose in hifi audio the area of investigation which seems ripe and obvious it would be looking at dynamic behavior instead of static behavior.
Why would mfr’s focus on distortion at rated power when the average power level may be tenths of a Watt (partly out of tradition, tubes amps produced distortion which increased with level while below some power level, many SS units increase umm).
Anyway (to paraphrase Firesign Theater in Giant Rat of Sumatra) “Measurements are a tool so powerful they can only be used for good (providing valuable clues on what needs to be fixed) or evil (separation of cash and wallet).
Best,
Tom Danley


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