Originally Posted by ComfyGrados
And if I understand correctly, not all headphone manufacturers compensate their measurements that way... don't some headphone manufacturers aim for, for example, a target diffuse field curve like a mean average human ear diffuse field curve?
After all, the most important ramifications of this sort of discussion and research, in terms of what our ears think, is it all some day leading to better sounding headphones!
Just try to draw a couple graphs and you'll see it's not universally applicable. If a headphone has responce that sound identical to a flat speaker for a head, that only means its transfer function is identical to head's HRTF.
Let's assume that a DF frequency responce for head 1 has a slight hill at 5kHz (measured by your 1) ). Let's assume we have a headphone which matches that FR exactly. Subtracting the 1) FR from headphone's FR you'll get a perfect straight line. Looks perfect, right?
Now take a head 2.. And by some virtue that one has 2 sharp peaks at 2 and 3 kHz, just for example. Now try to subtract that from the headphone's uncompensated FR: you get 2 pits at 2 and 3 kHz and a slight hill at 5 kHz.
So it's more correct to have a personal HRTF. Would be neat if hardware stores would provide you with an HRTF measurement if you buy headphones from them.. Though it's not impossible at home either.
Originally Posted by ultrabike
Assume a headphone is designed to reproduce the same frequency response that a flat speaker produces when measured using mics in dummy head 1.
If I understand things correctly, if this headphone is placed on a different dummy head 2, the headphone's measured frequency response will be different from the response obtained through using the same flat measuring speakers using mics in dummy head 2.
If so, here are my noob questions:
1) Is the cause of these differences a result of the variation in "acoustic impedance" when using headphone on head 1 and 2?
2) Is "acoustic impedance" variation a result of the enclosure volume difference (and air pressure) between head 1 + headphone and head 2 + headphone?
3) If this is so, what is the enclosure volume variance and distribution across individuals?
4) What is the variance vs frequency, of the frequency response deviation from flat when using an arbitrary head 1 "flat" measuring headphone on a representative set of distinct heads?
5) How does these differences correlate with sound quality perception?
Are all these questions addressed concisely by the paper or/and some other papers? ... I just want to stop being a noob, or at least diminish my noobness level.
BTW, I also seem to like flat uncompensated frequency response (or at least not too much compensation), and I can see how binaural recordings would benefit from this, even if things are not perfect
I also wonder how close the Smyth Realiser is in achieving optimal results with regular and multi-track recordings. Seems they standardized their product to work with the SRS-2170, and may offer some HRTF customization.
I must warn that I'm no specialist either! I first have to at least thoroughly study papers MM sent to me, not just read them quickly. So what I'll say next is a supposition, not truth.
First, it's even more variable than that. Even if two headphones measure exactly the same on one head (FR-PR-square-impulse etc), they could measure differently from each other on another head.
1) Seems that it is indeed caused by variation of acoustic impedance, which causes different resonances to arise. Possible resonances are determined by exact pinna and canal structure. Equal impedance + equal IR seems to result in truly equal sound.
2) Enclosure volume plays a role to, but mostly it seems proportional to how much of the open space around is shrouded by headphone's structure.
3) Don't know. Variation in personal ear resonances seem to be very high from what I've read, though sources aren't very reliable.
4) In Moller's paper, all tested headphones had under +-6dB difference under 6kHz, and measurement of variation over 6 kHz was deemed impractical (I have to reread on that! maybe I misunderstood that part)
5) Seems to be more important to localisation than tonal balance perception, but high peaks would probably cause brightness of sound ( so a HP bright for one may be alright for another one even objectively)
These questions are addressed in papers, but I won't say if the extent of how well they're addressed is good enough for me.
Staxes seem to have one of the lowest acoustic impedances, as they're literally very acoustically transparent, so they're well suited for that task.