It’s an interesting discussion and I do feel that it’s getting addressed in a more balanced way than other places.
I have read Head-Fi, ASR and even some Archimago.
I have some take aways.
First, measurements are taken using a sine wave or a test tone, it’s not music, it’s a flat, 2 dimensional tone.
Stereo music isn’t flat. It’s two 3 dimensional signals interacting with each other. This, along with our brain’s ability to interpret, is what gives us imaging.
That tone also has very tightly controlled time alignment. It’s a pure wave that is generated. Music isn’t that. It’s complex and, when you listen to DAC designers like Mike Moffat and Rob Watts, they are very concerned with getting the time and frequency domain right in their products. Something that I’m not sure would be measurable on SINAD, THD and FR.
I’m not saying that those measurements are worthless, just that they don’t have a complete picture. It’s why a headphone that misses the Harmon curve can be pleasurable to listen to.
My second thought is that we are all different. My wife has significant hearing loss in one ear. She will never hear true stereo imaging like I do. This upsets me. Differences in our physical ears and nervous system, will change how each person hears something.
When you talk to 2 channel audiophiles using speakers, everything is dependant on the room and the interaction with the room and the speaker. I feel that with headphones the shape of your actual head starts to play a part.
Amps to me, clearly make a difference. Especially, their interaction with the driver. It needs to be able to handle the impedance swings of the transducer and control it, especially when the technology differs, such as with a planar magnetic or dynamic driver. Some drivers need more current, some more voltage
DAC’s make smaller differences, again, I think the time domain stuff might make a difference. What I have observed is that to me, multi bit is more important on my 2 channel setup as it gives greater depth to the soundstage, whereas delta sigma gives more width, that is actually more useful on headphones. Not that they can’t sound good on both, just a difference I have observed.
Finally, music is art. Concert pianists all play the same notes in roughly the same timing. But there is still interpretation within that, that makes one better than the other.
If Leonardo Da Vinca also had a DSLR camera and took a photo when he painted the Mona Lisa, which would we prefer if he hung them side by side? Would the photo enhance or diminish our appreciation of it? Do we appreciate the painting because generations of art critics have told us it is a masterpiece? That last one is a bit philosophical for a Monday morning, my apologies!
Synergy is often thrown around and I kind of agree, but I often wonder if we truly understand how amps and transducers really interact with each other. Maybe the designers do.
I don’t think we’ve found the truth yet.