Comparing with my HD 598SE, which I have used as my main headphones for the last 4 years, the sound is punchier on the bass sound and all over more defined with more details. Compared to my AKG K7XX, which I find sounds flat and boring with a lot of music being muddy, it has more details, more punch and more focus on bass.
I would not describe them as dull or hollow. I would describe them as clear treble with punchy bass and mids.
My serial starts with 0855, I've just started with better headphones so hope it helps.