Back around October I bought three sets of headphones. Two for the kids and one for me.
I bought the kids something called Sennheiser 280 Pro and the fact that they did not hurt their ears or heads (physically from the strain of keeping them on) made them instantly love those 'phones.
Mine are my fourth set of Sennheiser headphones referred to as a part of the 600 series. My first were purchased in the early seventies and I replaced them again and again.
My knew ones are called HD 600. They sounded GREAT, right out of the box. My kids' phones sounded fine as well, but mine had a depth of detail that far exceeded the detail and quality of the 280 Pros.
Well, my kids have listened to theirs something approaching "constantly" since I bought them. I have only listened to mine for a few hours in that length of time; I usually listen to open speakers, not headphones.
What really surprised me is that yesterday, I was at the computer and my son's headphones were hanging on his rack on the desk and I grabbed them for my session of computer time (I still do fractal art) and listening. To my amazement, HIS headphones, one quarter the price of mine, sounded BETTER than MY HD 600 'phones!! AND they sounded way better than I had remembered that they had sounded when I bought them.
I suppose my point is to Odeon, who has just recently bought some nice, upper grade AKG efforts.
Mine are barely starting to break in because I do not use them that much (they sound fine anyway, BUT...), but my son's 'phones are well broken in and even though they are a mid grade, they sound amazing!
I can not wait to hear a kind of report from Odeon after his new 'phones have been broken in for about six months or so. (I plan to cheat, after hearing the difference in my son's set. I am going to set mine to play at a moderate level all the time, even when I am not there, just to enhance the break in process.)
I just had a very real example shown to me by accident which demonstrated the importance of a decent break in period before assessing an audio (speaker, most especially) device.