castleofargh
Sound Science Forum Moderator
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instead of listing flat headphones, it's safer(and more realistic) to assume that none are because we are physically different people expecting a different neutral. also http://seanolive.blogspot.com/2009/10/audios-circle-of-confusion.htmlBut what's flat? Music is dynamic. One headphone may be notably flat playing a stand up bass with sustained notes. But add in another bass signal - say short sustain drums (rototoms) and they start to modulate each other - than its not flat. The best headphone I ever heard on that test is the HD-600, but the bass under 65 Hz is lacking, and if we could assign a "Q" for the bass I'd say it was very damped (.57), and to support that I'd say the impact even in the midbass is minimized compared to other headphones and a large number of speakers I'm familiar with. The HD600 bass would be closest perhaps to panels such as the .7i, or the fairly unknown Cizek 1 w/ bass set to .57.
So in the real world "relatively" flat is subjective based on what you have heard, and what you prefer. I'd say listeners would have to be educated a good deal not to make their reference based on their preferences and/or lack of exposure.
For me the HD-600 and HD-800 would be flat frequency references. But there are things missing that makes the experience at times - astringent. My HE-500 modded with MrSpeakers Ether Flow Angled and the fuzzor mod are just about as flat as the HD-600 but seem to capture music better (classical is close outside of the missing bass heft). But things like cymbals being brushed are far more realistic then the 600. So what's that? Harmonic Distortion? or the small spike at 10k?
Ever since digital gained market share I've seen the rise of tubes to balance that, and the high buck MC vinyl thing vs digital.
I think measurements can lead you to the area you want to be in, but that subjective choice will continue to be the decider (along with budget).
in any case, you'd want to measure stuff yourself to try and rule out unknown parameters once you're down that rabbit hole. for a 300ohm headphone it's not really important, because small mistakes, neglecting the extra cabling used to measure, and the amp's own impedance curve, aren't usually going to make any big difference compared to 300ohm and more of the headphone. but when trying to match theory and measurements on lower impedance headphones/IEMs, even my own low-fi measurements fail to be accurate enough to account for everything and give me pretty result strictly aligning to electrical laws. not that there is more to audio signal than electrical laws!!!!!!!! just the like with everything else, it can be hard to remove or control all variables in our circuit.Whoa, I think you might have lost me on the second calculation! So, most of the parameters required to calculate Zout_critical_damping are not in the public domain and can only be obtained by personally measuring the headphone, is that correct? Or do you have already have enough information to estimate it? If it's not too much trouble, would you mind walking me through one example please?
another point which is only my anecdotal experience fooling around with resistors, an EQ, and a mic, along with something I read long ago somewhere that may or may not be true(check that endorsement!^_^): changing the damping ratio for headphones and IEMs, isn't IMO, as significant as it can be on some big fat speakers(FR non withstanding!!!!!!!). if you make sure to compensate the frequency response, the changes aren't all that, subjectively. IMO, it's yet another case of being misguided by how an impulse response may look. if you look at the impulse response out of the headphone, you'll wish to get critically damped stuff all year long, but I'm of the opinion that impressions of differences will come from many other places and shouldn't be assumed to all be the headphone and all be electrical damping.
also in the case of your own amp, there are a few out of the ordinary things in it(starting by all those impedance settings), so you can't rule out that the amp itself may change sound on its own in some audible ways, when those impedance settings are switched.