Best mids and soundstage in circumaural headphone?

What's wrong with the mids on your AD900's?

K-701 http://www.head-fi.org/forums/f4/k702-studio-393139/

You should look into the Sennheiser HD600s. They are known for their more mid range orientation. I have seen quite a few threads about people being very happy with their HD600s with the HD650 cable. There are a few threads on the first couple pages you should read regarding the HD600 and HD650.

Just an option.

The Sennheiser HD-600 is pretty good for that kind of music, but the best for mids and soundstage are the AKG K-501 and K-1000. Grab the K-1000 if you can. It is everything you want and then some. I even think it's worth going into debt for. If you want the same sound signature in a more affordable package with less (but still excellent) soundstage, get the K-501. The K-701 will probably be mentioned a lot in this thread. I've owned all of these headphones for one to three years, and I think the K-701 is the weakest offering. It's not bad, but it has a lingering unnaturalness that I've never developed a taste for. Besides, a K-501 can be had for half the price of a K-701 and you'll get better sound.

A couple other contenders would be the AKG K-240DF and the Beyerdynamic DT48. Neiher has the soundstage of the K-501, but both excel at vocal and acoustic music. Especially the DT48; it gives you detail you never knew existed, tonal accuracy and a lightning response. The DT48 isn't for everyone, but if it suits your musical tastes, almost nothin can touch it.

As uncle erik suggested, I love the k701s and would recommend them for your purposes, but I also agree with him that the 501s may be better than the 701s. I have heard both (though I didn't hear the 501s for very long), and I think that the unnaturalness that uncle erik mentioned is due to the 701's soundstage. It is, and sounds, artificially large. Something is just not right about it. With the 501, I didn't have that same feeling. They felt natural and right, with the same general sound sig and resolving power of the 701s. I might have to get a pair eventually. However, I am one of the few who thinks that the 701s really look good, and I might keep them as a second can for that (being as I don't hear a huge difference between the 501 and 701)

Budget? If you can swing some cents then it won't get much better than the O2 Mk1, period. Not the most gigantic soundstage in the world but probably the best imaging you can get in headphones period, and mids to die for, provided that your signal path doesn't suck and your source has nice mids to begin with.

A K340 has some spectacular mids and soundstage. It's actually quite similar to the O2 in many regards, though the O2 is in a different league overall. There are many versions of K340s, and I've heard pretty much all. My favorite is a stock bass-light pair from really good but lush tube equipment. It retains the sparkly though not overbearing highs that good K340s have, has that spectacular midrange, and a large soundstage with razor-sharp imaging. But, good luck finding a pair that sounds like that. They're rare, especially unmodified.

The SR-003 has an amazing midrange but soundstage is only large on specific equipment. Still, don't discount the form factor and low cost, these headphones kick *** in the right rig.

HD650 well-driven will have a great midrange and soundstage, but you'll need a lot of juice behind it, and preferably balanced drive. Otherwise, the HD600 has a more natural midrange and a more open soundstage, but its imaging is nowhere near as sharp as the HD650.

K701, K601, K271.

$800?

How about a used K-501 for about $150 and the Magnepan MMG for $599? You could power those with a used vintage receiver for $50 or less, if you have an old one sitting around. If you're looking for soundstage, nothing beats a dipole. And if you love vocals and acoustics, nothing beats a planar. If not the MMG, keep an eye out for used ribbons, electrostats, planars, and AMTs. I think you'd love a pair.

Should this soundstage be realistic or just impressive? If the former - AKG K601, Grado GS1000, Beyerdynamic DT880 Pro with kind of sweetness added to the midrange, for just big soundstage add the K701's and the HD650's to the list. HD600 - no way, neither best mids, nor best soundstage.

I am not familiar with any AKG but Sennheiser may fit your bill. Especially the HD650 will give you this 'wall of sound' and thicker mids I think you will like.

If you are saving up for a speaker rig anyway, I will x2 the recommendation for planars and the 501s. I have a pair of Magnepan tympanis that were made in 1976 (they were my dads) and still sound perfect and have a midrange to die for.

On closed headphones I would say DX1000.