[Royal Amethyst]

I've given the HD 518's about a 30 minute listen so far. They do seem somewhat more bassy. And, I don't know if there's a correct audio term for it, but "louder"? Like... they sound like what I think my HD 598's would sound like if they had an amp. Maybe the sound is just colored more than the classically neutral HD 598's.
With EQ settings, I can force a lot of punchy bass out of the HD 518's so far. Even with the HD 598's using the same setting it feels "muted" for lack of a better term. The HD 598's seem adamant about remaining as neutral as possible. They still sound wonderfully clear, but the HD 518's have a more "fun" sound for pop, rock, and metal.

 

[WilliamLeonhart]

Listen more and you'll see that the HD598 has bigger soundstage and more refined details than its brother. The HD598 is far from neutral, it's just that they try to create a relaxing, clear sound.