My Sony MDR 1R has almost 100 hours of burn in now.
I find them to be highly coloured headphones.Although the overall balance to the sound is not bad,and soundstage imaging and detail is good,the sound is covered with a veil which made the sound very warm,from midbass to mid highs.This,combined with the reduced presence in the higher frequencies,make the sound to have almost a magical timbre to it...If you adjust to it,it isn't bad,and ears and brain get used and then it seems that the balance is right...
But when I switched to some of my other headphones after listening to sony's,(like shure srh 840,akg K550 ,krk kns 6400,sennheiser hd600,koss ksc 75),they seem to be treble heavy,with unnatural thin and hollow mids...But all these don't have the wrong tonallity,sony is to blame because from midbass to midhighs is too coloured.I've never experienced such a big difference in tonality when switching between my other headphones.There were always difference between them of course,but not to this extreme extend...
I'm not sure if this is due to it's pleather erapads and fit and not the drivers,but I guess that sony gave them this tonallity on purpose,because when a company designs a product,they take into consideration every aspect of the design and how it change the sound.
If someone likes this sound signature and enjoy it ,then that's all that matters,to enjoy your music...
But in my opinion,if someone wants a normal tonality and balance to their headphones,you'd better look elsewhere.I personally find them to have a faulty sound balance that if I get used to it,I'll not be able to appreciate other good headphones out there.