Everyone has diff hearing therefore the measurement is done by the freq chart.
YOU CANNOT base on your to judge if the headphone is neutral or close to neutral.
I've said before you need lot of experience in the highend gears to realize that d7100 has bad distortion at the lower freq.
People here don't get that.
I am not going to say anymore its like telling beats fanboys that beats hps are not worth $300.
You lose on this, not me.
About the distortion. I don't know what you are saying. I have years exp with HighEnd gear and can't hear any distortion. Unless, like some people here, you have connected them to portable device . Then u could of heard the distortion. I had them connected to mobile devices and tablets ( have few at home ) despite what people here where saying. They sounded horrible off any portable device. Xperia Z, Nook HD+, iMac 2011, iPod Wolfson DAC- all same sh...ite.
D7100 needs a lot of current. Because thats how they are build, with low impedance, thick coil, unglued edges of drivers and wooden housing, they can take 1800mW !!! almost 2 Wats ! HD650 can take 200mW max! By this and by experience I know they need loads of current and SS Class A amp to sound best. I suppose most tube amps will have slight difficulty handling them because of harmonic distortion adding while pushing mids. The best amp as I think would be, SE Class A amp with "warm" sound signature ( Properly applied Class A does the job ).
Currently I'm running them from my Modified Vintage Grundig V1700 ( 100ohm resistor only ) , transport, HeadRoom Dac, and they sound absolutely stunning. While with Fiio 12 and Rega Ear MK II they where so so, not impressive not horribly bad.
If you have years of experience with HighEnd gear you would notice immediately that D7100 needs proper amping, and very selective, difficult component matching. Like most of the floor standing HighEnd speakers.
Amp I would choose for them: And suppose Ill buy one of them in next 3 weeks.
Lake People 103 or 109
Maybe Yulong A28