high power tube amps vs ss

"An excellent example is how some amps can sound bright, but measure the frequency response and they are perfectly flat. "

The ear sensitivity chart in the diagram I shared alone would seem to explain that. We don;t hear bass as well as other frequencies, so when response measures flat, bass may be less heard. But that is how our ears work, so it is what it is. ITs a clear alternate example of how we hear what otherwise measures differently.

The huge unflatness of the ear sensitivity chart would also seem to debunk any claims one might make about being able to hear flat frequency response. If you hear it as being flat, it in fact cannot be. Significant equalization would have to be applied to the source to have any chance. At that point, what you hear as flat would no longer be natural, rather "enhanced" to make it sound that way to compensate for lack of flat response with our hearing.

The huge unflatness of the ear sensitivity chart would also seem to debunk any claims one might make about being able to hear flat frequency response. If you hear it as being flat, it in fact cannot be. Significant equalization would have to be applied to the source to have any chance. At that point, what you hear as flat would no longer be natural, rather "enhanced" to make it sound that way to compensate for lack of flat response with our hearing.

Its more complex than that, our ear/brain system can recognize acoustic environments and compensate for them... BTW I hope you are not suggesting that we need to compensate our ears with EQ.

I have trouble understanding how the ear hears something as "bright" that does not evidence itself somehow when measured.

I've always taken that as some resulting frequency anomoly in one of those frequency ranges where the ear is most sensitive, but how serious can it be if not even measurable? Where is the evidence that the effect exists, much less the cause?

If we can't measure it can it exist? Sure! Our instruments have limits of their own- noise being an excellent example (another being the tendency to quantify a phenomena as a reading on a meter...). When an amplifier has low harmonic distortion measurements, its often described as having such low distortion that its "buried in the noise of the instruments".

The simple fact is that in regards to sensitivity to odd ordered harmonics, our ears are **more** sensitive than instruments. This is not hard to understand if you also know that the ear is that sensitive because it uses odd orders to gauge sound pressure- look at it as a survival trait. If you can't tell how loud a tiger is growling, you may well soon be dead. The ear needs to be pretty sensitive as a result. There are other things that the ear sucks at compared to instruments; this simply isn't one of them :)

General Electric did the studies of this phenomena back in the 1960s. It was perhaps one of the first real forays into the hows and whys of human hearing perceptual rules. We have learned a lot more since then.

"If we can't measure it can it exist? Sure!"

Sure. But some actual evidence always helps, especially in the often twilight zone of high end audio.

If you can't measure it, it does not prove it is not there, just that there is no evidence to substantiate it other than words and theories.

Plus once it is determined to exist the next question is how important is it really?

ANy issue can seem quite grand on its own. But put it into the big picture along with all the rest, and maybe it is not really the biggest nut to crack? All designers have their pet peeves that determine their approach. Designs are different as a result as are the results themselves. Which is best? Each woth their salt thinks their own most likely. How to determine who is right and who is wrong? Evidence certainly helps. Substantial evidence often takes a long time to accumulate to the point where determinations can be. But time usually tells in the end. We'll see....

Atmasphere, I've found that chart to be a useful tool to help me understand audio better. What I have heard over the years is consistent with what the chart tells me.

IS there some way you can reconcile the theory you support with the chart? For example, do the harmonic loudness artifacts you describe commonly fall into the frequency ranges depicted that ears are most sensitive to? That sound plausible to me. If what you say is at least consistent with the chart, that adds something to the case IMHO.

My understanding as documented on the source site is the human ear sensitivity data depicted in the chart is based on data collected "testing large sample groups" and is based on ISO standard 226 (2003) for human equal loudness contours, whatever the blue heck that is.