Of course it needs a DAC / headphone amp to sound at its best. It doesn't sound bad from an iPhone or from my Macbook's line out but plug it into a Benchmark, a Weiss or a Phonitor to fully experience its capabilities. To me however Edition 8 is the better headphone. While Signature might be the more accurate (although darker sounding), Edition 8 has a finesse, a certain something very difficult to describe that takes ages of burn in to come forward, but once it does, it makes for a very special, enjoyable, addicting listen. Signature is smooth sounding but rather closed, dark and certainly lacks this finesse factor (although I can't exclude the benefit of further burn in, Ultrasone are notoriously slow at reaching their full potential). I think Ed 8 also images better, the soundstage is wider and more convincing, almost as good as an open headphone experience. It might be that the shape or positioning of the drivers works better for my ears (as you know S-Logic is very dependent on anatomy) but Ed. 8 scores higher in my book. And coming from HD800 or Edition 8 I find the highs of Signature slightly lacking, not in quantity (I am certainly not a treble fan, on the contrary, I am very sensitive and it took a long time and a SPL to fully appreciate Ed. 8) but in quality. It simply doesn't have that life-like quality of the more expensive rivals. Overall Signature might appeal to people who find Ed. 8 too bright but an improvement, in my opinion, it is not. The mids are still recessed, the treble is darker, the soundstage is rather claustrophobic and the magic of Ed.8 (I think Muppet Face called it euphony) is missing. Again, extended burn in might help. But they're certainly not one and the same headphone, they're quite differently voiced and for me, at this point, Ed. 8 is the clear winner. The build quality is also better (as sturdy as this plastic frame might be it's no match for the all metal Ed. 8) and don't forget the 7 years warranty for the Edition series (I have the Limited version). On the other hand Signature is a big improvement over 2900 Pro and a chance to taste the high end Edition sound at a fraction of the price. I can imagine why some people, especially using a simple line out from a Macbook / iPhone, might find them very similar or even prefer the Signature, which, due to it's darker sound signature, would cope better with sibilance / lower quality recordings.