Hi,
I would say that the Beyers, AKG and Sennheisers are the exact opposite sound wise from the AT and Grado.
I find both Grado and AT overly bright. If you like this sort of sound, you will hate the European headphones. You will find them too dark and too slow.
I don't have much experience with Beyers, so I will let someone else espouse in detail on their strengths and weaknesses. I will describe Senns and AKG's to you.
Sennheisers: These are my favorite headphones. Frankly, I've never met a Senn I didn't like. Needless to say, the higher you go up the food chain, the more refined the products become. I like the following characteristics of the Sennheiser house sound:
1. Laid back - You get the impression of sitting in the middle of the concert hall, rather than right along there on the stage with Grados
2. Soundstage - Senns have a very deep soundstage. You can tell which instruments are closer and which are further. Grados tend to flatten things out.
3. Liquidity - The senn sound is very lush and liquid. I find them very musical. They are not the ultimate in detail, although they are very detailed, but whatever detail compromises they make, they make in lieu of sheer musicality and flow.
4. Deep bass. I think that Senns probably have the most extended bass of any headphone (at least any headphone that I've heard) Bass is deep, rich and detailed, never sloppy
5. They grow with your equipment - Senns never offend. However, the better your equipment gets, the better they sound. They're like flowers that open up as your source and amplification equipment improves
6. Comfort - Oh my! The most comfortable headphones I've ever experienced! I can listen to them for hours and I forget that I'm wearing them. Such a nice fit and comfort. Lovely! Like wearing ear muffs.
Limitations:
1. Not the fastest phones on the market
2. Can be a bit dark especially the higher end models
3. Can be a bit veiled without cable upgrades (especially the 580/600 models)
4. The higher end models require an amp to shine.
AKG
I'm really on the fence with regard to the AKG phones (I've only heard the higher end models: 501, 601, 701, k1000). They tend to be more neutral than the Senns and I can't say that they do anything wrong. However, I do find them a bit dull and lifeless. They don't move me the way the Senns do. I can definitely see why others may love them, but to me, AKG's are like a good technical musician who plays everything correctly, but has no soul.
What AKG's do well:
1. Neutrality - probably the most neutral and uncolored headphones I've heard. I think that if I were recording, AKG's would be the phones I'd use.
2. Speed - Although not as fast as Grados, which are the speed champs, AKG's are faster than the Senns.
3. Scale - These phones scale nicely with your equipment. Perhaps not as dramatically as the Senns (that point may be debatable), but as your equipment improves, the higher end AKG's will be able to hold their own
4. Soundstage - not as deep or as wide as the Senn soundstage, but quite nice. Accurate instrument and placement imaging.
Limitations:
1. Dull - my biggest peeve about the AKG's is that they're soooo boring. Others may disagree on that point, but to me, these things are just lifeless and robotic.
2. A bit on the dark side - Whereas these phones are very neutral, they tend to be on the darker side of neutrality. If you like bright phones, these ain't it.
3. Amplification - Amplification is a must with these. I find that they're much tougher to drive than even the Senns and amplification matching is more crucial than the Senns. Senns are very forgiving in that regard.
4. Comfort - Not quite as comfortable as Senns. I don't find them to be as well balanced on my head and my head gets fatigued after a while.
This is pretty much it, in a nut shell. Perhaps others can fill in the blanks if I have left any.
