^ this ...
The AKG 700-series phones are known for demanding a lot of current. Comparison with high-impedance headphones is not valid (referring to previous posts, not this one), because as noted above, power at 62 ohms requires much more current, not voltage, and the AKGs have never been known as easy to drive (like the HD595/8/9). Keep in mind that the bass will still be on the light side compared to many other phones, but they are able to go very, very deep.
I prefer the original K701 to the newer implementations (except the center bump!). I have a very-low serial number, original K701. I've also owned a K712 and sold it - likewise with the Massdrop K7XX version. Along the way, they took out the center dot covering the port at the back of the driver. It increased bass quite a bit, but a lot of the outstanding air and soundstage went with it. Massdrop added foam in the vented can (unless someone did it first with the 702 or Q702 - never owned those) and made things even worse, IMHO. The K712 never had the foam, at least in my version (Austrian made), but it just seemed like the distortion was pretty high, sounding "crunchy" on peaks. I could never listen to them for very long.
I'm going to keep my K701, though.