how long did you let them burn in? Did you take foam from the middle of the pads? EQ of your source off?
Streatch them and they become more comfy. Hold the metal band in your hands and streatch it out, pressing on the middle with your thumbs, dont over do it otherwise you may break the headband. After all this tell me what you think. The highs are not tinny at all, bass isnt very boomy, you can also try the blu tak mod. All this is in my AKG K81/518 DJ/LE thread.

I hope you took the extra foam layer out from the earpads. It makes a big difference in reducing the bass. The K518 are great for the low price. Of course there are better choices out there, but then you have to pay a lot more. My Sennheiser HD25-II sound better than my wife's K518LE, but no three times as good, which is how much more the Sennheisers cost compared to the AKG.
You could always follow randomkids advice in stretching the headband out. On the pair I got for my wife, I stretched the headband out over a box with about the same size as a human head. I also bought a spare Sennheiser HD25 headband pad (http://images.junostatic.com/full/IS425399-01-01-BIG.jpg) and glued it to the headband of the K518LE. The result is a much more comfortable headphone, with SQ that is just slightly below that of the three times as expensive HD25...

- I use them every day for about half an hour (I still haven't given up on them) so there must be at least 100 hrs on them;
- tried different EQ's and eventually stuck with reducing bass, which in some way is defeating the purpose of buying them in the first place, but I prefer this to that upper bass rise;
- I've done the stretching and it certainly helped in reducing the pressure on my ears.Problem is, the headband now rests with more force on the top of my head, even though I use the largest setting (maybe my ears are too low?);
- I've removed (and replaced) the foam inlays, which, to me didn't do that much basswise, only raising the 'scratchiness' a little;
- don't get me wrong; I still gave these three stars, because I agree that they are not too shabby for their price. I just wanted to lower the expectations for future buyers a little, so they won't be as disappointed as I was.I think the Sennheiser PX 200II, which are more or less the same price, look less cheap
- I'm familiar with HD25 which to me, sounds a lot more mature with real bass where it's supposed to be. However, to my ears they suffer from the same 'scratchiness' in the upper highs. I wish I could explain this better. When I said tinny, I meant that literally. It's like a tweeter with a aluminum dome in an overly bright speaker. It's as if the diafragm is made of metal (which as far as I know is not the case);
- I'm considering the blutak mod.

Well, you might be sensitive to treble. I understand what you mean when you describe the "tweeter-like" scratchiness. I did hear some of that when my HD25 were new out of the box. Now that scratchiness has settled down. I feel that the K518 has got a less forward treble compared to the HD25.
I'd definitely describe the HD25 as more balanced than the K518, but with the foams removed the K518 becomes pretty balanced. You can hear that there are mids, for example.
Anyway, my wife is amazed with the sound. But she was coming from iPod buds and some sort of "cute" earbuds that sounded 10 times worse than iPod earbuds...

It all boils down to preference and reference, my reference mostly being AT-W1000 and PX200.
What I really would like is the sound and comfort of W1000, the portability of PX200, the bass of Beyerdynamic DT880, the air of HD800 and the isolation of these K518DJ. Is that too much to ask?

just put sennheiser velours on mine, literally a couple of hours ago, now the isolation is less, but the pads are super comfy (pain in the a** to get on tho) it came with self adhesive headband pads, and it has brought the bass down, i can now say they could be nealy on par with the HD25-1. Now there are more highs, and less bass, balanced now.

Haha! Well, it's almost impossible to get a pair of headphones that crosses all of your boxes. I enjoy my HD25, but with bright recordings they can be a bit too much. Also there isn't much of a soundstage. My ATH-ES7 sound much more fun than the HD25 with nicely colored mids that works great for guitar driven music. But the ES7 are nowhere near as detailed. I sort of see the K518 as slightly similar to the ATH-ES7, but with a more dry sound and slightly more flabby bass.
In my hunt for the ultimate portal headphone, I'm considering buying the ATH-ES10.
If you look at my gear you will see that I already have too many headphones. But it is a sort of addiction. I'm also an earbud collector, and my favorites (so far) are the ATH-CM700TI, which have a very detailed and at the same time laid back sound. And a great soundstage. But as with most earbuds, they do not have much bass...
This is an expensive hobby!