Here are a few impressions of the AD now that I've had a chance to listen for a week.
1. Treble. I prefer a darker treble as I'm sensitive to bright hp's. I was worried that the AD was too bright on the treble...it's not. It is "more extended" than the MD and makes them sound very dark even. But while the AD treble is nicely extended it's never harsh or strident. Excitement up top without fatigue.
2. Mids. Incredibly grain free and natural. Not recessed and not forward. Female vocals are beautifully rendered. Tone of vocals sounds spot on. Melody Gardot sounds dreamy...inside my head, easy to get completely lost in the vocals.
3. Bass. Goes deep with visceral impact, but still balanced with the rest of the sounds. I love the linear effect. The sub bass is addictive. Fink: Perfect Darkness is LOTS of fun on the AD. Never out of control..hits real hard...makes me smile every time.
4. Imagining is a standout. Like a good pair of floor speakers. Nothing about the signature is out of place. Very balanced.
5. The bass adjustment is fun. If you push it too much you'll get a mid bass suck out. Never fully open the port to the point you don't see the set screw at all.
6. Beats the MD hands down. Easily more gifted across the spectrum than my hd650. He400...there is a touch more sub bass impact on the 400 but if you were blindfolded I'm not sure you'd be able to pick it out. He500...AD still better...sound stage a bit better on the 500 but I'd pick up the AD every time over the 500.