I finally got on with my review. I am writing it with a very special approach and not judging it at all from listening to music or anything of that sort, that would make it subjective. I decided to test it technically.
I think what you wanted to say is that there is no universal “flat” for our ears, but technically there is “flat”. It would be a frequency response that doesn’t have boosted frequencies and is as flat as possible - we all know perfectly flat is non achievable. How do you test if something is flat technically-wise? Measurements.
Now, there is controversy in measurements as well. If you use a G.R.A.S. measurement system that has one of those heads with ears… you cannot really use that as a standard because everybody’s ears are different. I concluded that the most objective way to test if a headphone has a flat frequency response would be by having measurement microphones and headphones without much obstacles. I had a chance to visit a friend of mine and use his measurement system, he didn’t tell me what exact mics he used but the setup was pretty sensible. He just told me that the mics were pricey, ideally I want to know what mics he used. He used two different softwares (I also didn’t ask which ones they were).
Instead of an ear, it was this circular mounting system, no obstacles that would cause reflections (other than the headphones themselves, like their ear-pads for example), so it was as technically accurate as it gets (unless you have more expensive rig I guess…).
From my findings Ollo S4X had what I could safely call a “perfectly” flat response, at least the mid-range. From listening to it, I did find it to lack the deeper frequencies, I also didn’t find it to hit the highest notes (to my ears).
I think this is the best way to make a flat headphone. You are not making it for a certain ear, you are making sure technically-wise it is what it claims to be, and sure as hell it proved itself to have a flat frequency response. This means that the subjective part will be the fact that different people will interpret this flat frequency response differently, but that flat frequency response stays objective (I believe). Maybe our sight could be compared in a similar way, we don’t really know how our perception of vision differs, but we all call “red” red, and a “table” a table. It’s not really easy to find comparisons, maybe somebody can contribute with comparisons so it is easier to understand this.
My conclusion is to make a headphone technically correct, if a user wants to trust the technical side of things, that would be the standard. However, if he wants a “flat” or “reference-grade” response for himself, he would need to have a headphone made ONLY for himself, this is the only sensible conclusion I made. A manufacturer cannot make a truly reference-grade headphone for everybody because he doesn’t know whose ears will be listening to it. But what the manufacturer can do is to make sure that the product is technically correct and “doesn’t” have coloration, this would be a flat frequency response - however, it WILL be interpreted differently by everyone, but this is the only solution that makes sense.
What does everybody think?