HD800 are certainly what I would call chameleon. Another phone that is like that is the HD650. For a dark headphone it sounds characteristically different from different amps and sources. The HD800 and HD650 also respond quite dramatically to balanced drive... more so than the Hifimans and Audezes that have come through here. Actually I think both those Sennheisers are far more chameleon than the HE-500, LCD-2 r1 or 2.

HD800 are at least a gear chameleon more than track chameleon. Or rather, their ability to sound chameleon-like (ugh, what the hell is this word) depends on the gear used to drive it. From my experience, it's not balanced vs unbalanced - they don't seem to matter one bit. Just try the adapter from balanced to unbalanced on the same amp to check.
It's not output impedance alone in this case - it's more like it makes amplifier's distortion stand out because it has little of its own. (Also FR rolloffs.)

If you apply an equalizer to them (or some mods? I've heard them stock only and with balanced cabling mod), they do sound very adaptable - bah, let's use the proper word: accurate. Otherwise, the bright coloration reduces this ability considerably by messing up soundstaging.
That said, their dynamics and detailing is probably the best regardless.

--
rhythmdevils, you're quite a troll, you know that?

By the way, how is the term "sweet" defined exactly? I keep on hearing it from a more non-audiophile crowd for treble, I never really got it. Is it supposedly a less dry and airier treble?

I would think it is about similar to velvet(ty) highs, in other words 'soft' opposite of piercing (peaky) or coarse/rough highs.
Some, leaning towards coarse, recordings could sound more pleasant from a 'sweet' headphone.
Rounded treble or gently rolled off comes to mind while retaining small details.
Mostly combined with little elevated lows/warmish mids envokes the 'sweet' reaction.
HD650 comes to mind as an example.
Also one could call the older DT990 (600 Ohm) 'sweet' sounding eventhough it has peaked treble.

Ofcourse that is my interpretation of 'sweet'. 
It would be interesting to see what 'sweet' sounding might mean (describes what aspects) to other pirates as well. 

Bah, I don't want to turn this fun thread into a tirade about the pointlessness of balanced wiring for short interconnects - and why a good amplifier wouldn't care one whit about being fed differential, balanced or unbalanced (assuming it's designed for that topology), much less headphones. Never mind that the difference is not measurable, unless you have a ground loop somewhere.
The fact is that almost all DACs have balanced output, even these with unbalanced connectors - and nobody really complains.

Carry on, nothing to see in this post.

EDIT: Something to see here: minijack sucks for crosstalk. TRS works better. RCA/XLR/dual-mono jacks work best. That might be audible.

And while most DAC ICs do output a balanced signal many of them are converting it to single ended and then using opamp phase splitters to send it back to balanced out on the XLR. Ours is balanced all the way with no conversion to S/E

^This. So true. It's hard to believe how so many "high-end" DACs and CD players skimp on the balanced output portion with cheap op-amps.

Bah, I don't want to turn this fun thread into a tirade about the pointlessness of balanced wiring for short interconnects - and why a good amplifier wouldn't care one whit about being fed differential, balanced or unbalanced (assuming it's designed for that topology), much less headphones. Never mind that the difference is not measurable, unless you have a ground loop somewhere.

Using the balanced outputs (instead of the SE) from DACs do make a difference sonically, at least with the the two balanced DACs I own and on the Mjolnir and BA. Think principle of paralleling DAC chips (as opposed to noise cancellation / CMRR, etc.)

Heck, even the BA balanced output sounds different and slightly better from the SE output, despite that its an SE transformer coupled amp. No one knows why. There are a lot of things which are not measurable.

You mean bridging. It's well known to improve noise floor, might drop even order harmonic distortion too if implemented correctly, improve maximum current output. (3 dB in noise, 6 dB in harmonic distortion. Latter is rarely important, perhaps for some rare orthos.) Quite well-known and measurable. However, the same benefit can be had without actual balanced wiring in the headphones. Not that you shouldn't use it if you have one, but there's no real reason to mod them.

No I don't mean bridging. The BA is one single-ended amp to OPTs which are inherently balanced, not bridged. The balanced jack (without the common ground) does sound better. Deeper bass, more precise imaging, and possibly more resolving.

In the case of the DAC's, I guess you can think of the balanced differential outputs as "bridged."