What differences apart from the bass, hehe. Mmm , the midrange is a bit further back than on the 880, but it's basically the exact same quality, together with the airy treble it totally works for me. It's warm and clear, sparkly and detailed, with a beautiful midrange to hold things together...

The bass on the 880 is by no means bad , but always when I go to the dt 990 , I think to myself ah yes, that is the full sound I was missing. I think the 880 is really well tuned, it's just a matter of preference and the suitability to your music tastes. In my case it just means the 990 is the...

Try to get your hands on a nice used vintage Marantz or something. Nothing is quite as good with them imo.

The dt990 is the best of the three in my opinion. Granted I like them all three (very much actually), but all the qualities you get on the 880, you practically also get on the 990.   You would get the 880 if you really need the midrange to be that forward, and the 770 if you need something...

  Thanks, I was hoping you would respond :). I read on kent rockwell's site that he wrote the load of the dt880 is resistive and that makes them easy to drive, i don't know what he means by that, but I think it also has to do with why it isn't affected by the amp's impedance as much, is that right?

  That can happen if you for instance use an integrated amplifier where they put the headphone circuit with a high impedance, many have typically 120-150 ohm. I had this with my marantz pm7200, you can hear how the bass gets very loose, it was even worse on the hd598. But it also depends on...

DT770...

Why would I want to do the work of a company for them? And cables all sound the same anyway...

I would just go with the DT770... You simply retain the Beyer sound, yeah it doesn't sound totally like the 990 or 880. But if you like the 990 you'll probably love the 770 as well. I owned all three of them and definitely feel they are similar in many ways.

  But how can this be, the HD600 already scales infinitely?

I really like the DT880 and 990, but I have a special place for the X1 and X2. They just sound so right. HD600/650 are old man headphones. Haven't heard the AKG's.

  How much of a change is hard to say. If I say 5%... 5% of what? Still doesn't mean anything. I would say the midrange on the X2 is more pronounced, it sounds a bit airier. I think it's generally right on to say that the X2 is a more moderate X1. It still isn't a natural sounding headphone...

  Dunno, the X2 sounds a bit better all in all than the X1, but the X1 is lovely too. I feel that even though they are a bit different in terms of tuning, they still share the exact same strengths and weaknesses. Honestly I have to admit I kinda miss the X1's signature lol. Philips did a heck...

Honestly if people are that worried about sound 'leaking' then just get closed headphones and forget about open ones altogether.

  Probably because those amps all aim for transparency (I know for a fact the O2 and the DX do) and the only thing holding them back from it would be insufficient power. But as you seem to have noticed, the HD650 is quite an easy headphone to drive, because its sensitivity is very high. In...