On the subject of burn-in, I got around to testing my brand new pair against the 7520's I've been using for 6+ hours a day (as much as twice that sometimes) for more than a year.
I have to say I was surprised, because right when I bought them I did open the box up and do a similar test, found that they were almost the same, and then sealed them up again.
There is definitely a difference between the two now. Bass on the unused pair seemed "muddy". The bass extension was similar, but the unused pair sounded sluggish in comparison to the well used 7520.
Treble seemed veiled on the unused pair as well - it's not that there's more treble with the worn-in 7520, there's just more clarity with them.
So whatever the reason is, whether it's the pads being used for a year or something else, there's clearly a been a change with them, and I would definitely say it's for the better.
As for the materials, the padding seems to have held up well, and while the foam is a big firmer in the new pair, they're still about the same thickness. Actually, because I give them a wipe and fluff up the padding every week or two the used pair was slightly thicker than the new pair, because the pads have been pressed against each other for a year inside the box.
Originally Posted by jackson1
I can't verify this, but I've read that:
Sony have been forced to withdraw their excellent Professional series MDR-7520 headphones from sale in Europe because they don't pass the European safety regulations due to their high efficiency, power handling and attainable SPL.
That definitely sounds like a one of those stupid European laws. "Sorry, we have to ban your headphones, they're too efficient."
Their high efficiency and high power handling is what makes them great.