While I have never heard the cans you have mentioned (except for the HD800, briefly), I disagree with the notion of neutral sounding cold and lifeless. A good rig should sound like real life - which is by no means dull or lifeless. Although there is a basic problem with headphones regarding reaching neutrality; headphones will always sound different and from speakers, tonally or otherwise. Speakers come closer something sounding like a concert because of the different natures of the sound source.
Actually I whole heartedly agree with you in the context, and I think the actual difference is in the use of wording. The word "natural" is a much better choice, IMO. Neutral I think is described exactly as I said, and that is the only thing "neutral" can be. But I also agree with you, if we keep the wording in tact that "neutral" is not truly a desirable end result in audio equipment., and especially headphones and that "natural" is a more desirable destination.
The reasoning I think that "neutral" or "accurate" is a valid term (referring to the cold, lifeless, sterile sound) is that it is neutral to the recorded sound. What is on the recording is exactly what the microphones picked up in anechoic environment and exactly as the mixers and mastering engineers placed on that recording. A true neutral setup would not alter that and portray it exactly as it is. It is undesirable in the end result because what is on that recording is not true to life. It's a sanitized version by placing microphones at the exit apertures of instruments/mouths and keeping that sterile, unattenuated sound in tact through the neutral playback headphones. This is of course desirable in a recording so that the playback equipment/room can create its own live stage out of it without trying to reproduce some generic stage, which is what well colored headphones like HD650 set out to do. Reproduce that natural sound as it would be in real life.
There is however a place for such sterile "true neutral" equipment and thus why the term "neutral" referring to the cold, sterile representation that doesn't mimic real live performance is still a valid one to preserve. Recording. K702, HD600 etc are first and foremost meant as tools for studio work. In that environment, one looks for "neutral" as in, something that represents the cold, lifeless recording exactly so that one can verify that everthing is in good shape and that nothing is colored and biased so that end playback equipment (HD650, tubes, whatever) can add their color and build a stage without the recording telling it what stage to build. One needs such a "lifeless" tool to do that job. So neutral is real, and has a definite purpose. Also the study of music itself (composers, technique, etc) is helped by dead-neutral instruments.
So I agree entirely with how you evaluate the proper end point for audio gear. But I also think that neutral really does mean neutral which is by definition not natural. The cold K70x must do its job so that the lively HD650 can do its job
It's actually in interesting conversatoin that plays right into a few topics I've discussed in other threads. It's where I disagree with where much of the flagships are headed and disagree with the audiophile notion of extreme detail retrieval via such flagships. That kind of detail retreival is unnatural to live music presentation, and I feel at times that the HD650 level represents the peak (sans soundstage) of live music reproduction. The ultra detailed flagships may be moving away from lifelike sound and into something to detailed to be called natural for all but stage-level listening. Where HE-400 does excell over HD650 though is in a slightly more "fun", more dynamic presentation. HD650 has a bit of a DR compression of its own I think which is a little unrealistic but keeps it from being as fatiguing. For very dynamic classical for example I can hear all of it with HD650 on Lyr. With HE-400 if I turn it loud enough that I can clearly hear the quiet parts I'll get blasted away when the loud parts come Which is, of course, very realistic, if sometimes annoying... It's also where I peel away from the "measurements are everything" crowd and look at adding distortion via tubes, cables, colored headphones, colored sources, etc. It better recreates reality, not the sterile bit-perfect detail seeking quest some go on. HD650, HE-400 on tubes sound like real music being attenuated and distorted on walls and furnishings. Bit perfect SS amps and sterile headphones do not. And identically reproducing the sterile recording is not the intended end result of music playback, no matter what the measurement "tubes are distortion boxes" crowd may tell me!
Oh, and nothing wrong with taking HD650 and using it as the comparison of "neutral" to all other sounds. It's labeled "reference". That's what you're supposed to do with it
And besides, when you say 'unamped' the meaning is completely obvious, and not really viable to misinterpretation, so what's the problem?
Oh, I use it too, or rather refer to "needs an amp" often enough for conversation here. But often that leads to "it gets loud enough" wars. It's always best to periodically remind that we're talking about using lousy amps versus good amps, not using amps versus not using amps when the conversation veers toward quality
LOL, how true. And that ties into my conversation in this thread on cables where I referred to "the 'better' ones being 'well engineered inferiority'" which isn't a bad thing in that quest for natural over neutral, like with tubes I love when measurements type people cite "tube amp x measures terribly." Of course it measures terribly, it's a tube amp! I wouldn't buy it if it measured well!
But that's just it. Take multiple SS amps. If they don't all sound identical, they are influencing sound via such defects. O2 is almost dead flat in measurement. Any other dead flat measuring amp should sound identical. My Headroom Micro does not sound similar. It has very aggressive upper mids and a flabby bass. I dislike it in fact. But it is an influence on the sound, absolutely. Lyr...well tubes are tubes. I bought it because it does that, as you say.
DAC is a harder one because it is so much more subtle. I could easily ABX sufficiently different amps. DACs I don't think I'd bother trying. Arguably one is more detailed than another, and it probably is, but it's so much harder for the human ear to knowably separate unless it goes way out of its way to alter the sound (DacMagic for example does something that creates a huge artificial soundstage. A built-in DSP of sorts I presume.) However I find with a really nice DAC, I don't get fatigued by it. With a lesser DAC I am fatigued by the end of an album. It's a subtle difference somewhere in the sound that my brain doesn't conciously detect, but my ears do, slowly over time.
What to you mean with 'on the sound itself'?
With sound signature I was referring to the audible charactertics of sound. If it does not have an effect on this, then it does not have an audible effect at all. (except for things like gain and power).
By signature I mean the tonal balance. Generally (assuming SS) the rack shouldn't affect the tonal balance. But it is more prone to effect transient response, dynamics, even detail vs. muddiness. The control of the amp for example could make sound muddy or flabby bass if it lacks control of its own power output. It's an audible effect but it doesn't affect the signature in terms of tonality.