I've owned three different pairs of DT990s 2005 (250Ω) headphones over the last four years. The first pair broke after a year and I had to get them replaced through Beyer, the second pair had balancing issues between the drivers that I put up with for about three years until I just went ahead and bought another pair.
The first pair I had I couldn't say how old it was, but I bought it a year after the DT990 2005 was introduced (from Meier), and when I had them replaced I noticed interesting differences internally between them in regards to padding and so on. Unfortunately I don't have any pictures of this, and I had to send the old pair to Beyer when they were exchanged, but I'll try to describe it best I can. There were two main differences I could see, the first being that they put a protective plastic cover (like bars or a cage, you could say) over the driver with a white cloth-like material over it. My first pair you could literally press your finger against the foam insert and feel the bump of the center speaker cone, but with this cover on the second pair, all you felt was the plastic bars. My first pair started to rattle in deep bass notes and wouldn't stop, which is why I had them replaced, and I suspect the reason for that was some dirt or something got somewhere I couldn't reach. With the second pair, this never happened, and I feel like the new cover over the drivers played a role in that. The second difference was a thick white foam ring they put against the rear of the housing, with a hole in the center about the size of a US quarter, something I didn't notice in the first pair I got. Sonically I couldn't say what the differences were between them, as there was no way to A/B them, and any differences there might have been certainly weren't strong enough to notice without a direct comparison, aside from the issue of the drivers being imbalanced with the second pair (see my other threads for more detail).
The third pair I got (this time from Amazon) has the most differences, and since I still have the second pair I can show you pictures to illustrate the most obvious ones.
(yes that's seran wrap around the headband of the old model; it was getting sticky and flaky)
The cord shroud where it attaches to the housing has been changed from a slick smooth one to a (IMO less attractive) version with grooves. Whatever functional purpose this serves I don't know (other than maybe more flexibility), but the DT990 you get no longer resembles the one you see on the box because of this detail. It almost looks cheaper and more generic but I couldn't say if it's actually saving them money or something.
The other difference is more subtle and harder to see in the images, but I did my best to capture it. It's something you notice more when you're holding and feeling the headphones in your hand, but it's the velour cushions which have been changed from a super soft version to the stiffer one that I believe they use on the DT770. As you can imagine, with the denser stuffing this has a very noticeable effect on the audio characteristics as well.
The biggest is the treble. Both of the first two pairs had very harsh, sharp treble that was unforgiving on hot tracks with lots of sibilance. It made listening with these headphones a bit fatiguing even if you were used to it (which I was), and certainly limited the volume with which you were comfortably able to use. This was a big reason people made a mad dash for the 600Ω versions as supposedly they helped to address this issue (and I would have got that version if I lurked here more :-/). Well even though this new one is still 250Ω, the treble is MUCH more forgiving. I can't say if the pads are solely to blame for this or if it's something else inside, but I haven't had the mind to open up my new ones and take a look. If I did I'm sure I might find some other interesting things.
The other, less noticeable sonic difference that could probably be contributed mainly to the change in the velour pads is the bass. Unlike the 600Ω version that lessens this off and purportedly gives a more balanced overall cohesion with the rest of the audio spectrum, here we actually have MORE presence and more impact. It's a small difference, really, but it's there. For a lot of people that probably isn't good news, and of course if you have the amp to support it you should go with the higher impedance version as even Beyerdynamic themselves will tell you it's the superior version. But for whatever reason, should you end up with one of these newer 250Ω versions, either because it was gifted to you, or you don't feel confident in your amperage, or you're an idiot and didn't check the Head-Fi forums in like a year before deciding he wanted to replace his old messed-up pair (in which case you wouldn't be reading this warning anyway), then be prepared for some discrepancies between what you read in some older reviews and what you know about the DT990 and what you'll actually get in the latest batch of products coming off the assembly line.
On a side note, I noticed a lot less dependence on burn-in with this latest pair. The first two pairs absolutely needed it but this one hardly showed any difference afterward. I have no idea what I'm going to do with my old pair...
The first pair I had I couldn't say how old it was, but I bought it a year after the DT990 2005 was introduced (from Meier), and when I had them replaced I noticed interesting differences internally between them in regards to padding and so on. Unfortunately I don't have any pictures of this, and I had to send the old pair to Beyer when they were exchanged, but I'll try to describe it best I can. There were two main differences I could see, the first being that they put a protective plastic cover (like bars or a cage, you could say) over the driver with a white cloth-like material over it. My first pair you could literally press your finger against the foam insert and feel the bump of the center speaker cone, but with this cover on the second pair, all you felt was the plastic bars. My first pair started to rattle in deep bass notes and wouldn't stop, which is why I had them replaced, and I suspect the reason for that was some dirt or something got somewhere I couldn't reach. With the second pair, this never happened, and I feel like the new cover over the drivers played a role in that. The second difference was a thick white foam ring they put against the rear of the housing, with a hole in the center about the size of a US quarter, something I didn't notice in the first pair I got. Sonically I couldn't say what the differences were between them, as there was no way to A/B them, and any differences there might have been certainly weren't strong enough to notice without a direct comparison, aside from the issue of the drivers being imbalanced with the second pair (see my other threads for more detail).
The third pair I got (this time from Amazon) has the most differences, and since I still have the second pair I can show you pictures to illustrate the most obvious ones.
(yes that's seran wrap around the headband of the old model; it was getting sticky and flaky)
The cord shroud where it attaches to the housing has been changed from a slick smooth one to a (IMO less attractive) version with grooves. Whatever functional purpose this serves I don't know (other than maybe more flexibility), but the DT990 you get no longer resembles the one you see on the box because of this detail. It almost looks cheaper and more generic but I couldn't say if it's actually saving them money or something.
The other difference is more subtle and harder to see in the images, but I did my best to capture it. It's something you notice more when you're holding and feeling the headphones in your hand, but it's the velour cushions which have been changed from a super soft version to the stiffer one that I believe they use on the DT770. As you can imagine, with the denser stuffing this has a very noticeable effect on the audio characteristics as well.
The biggest is the treble. Both of the first two pairs had very harsh, sharp treble that was unforgiving on hot tracks with lots of sibilance. It made listening with these headphones a bit fatiguing even if you were used to it (which I was), and certainly limited the volume with which you were comfortably able to use. This was a big reason people made a mad dash for the 600Ω versions as supposedly they helped to address this issue (and I would have got that version if I lurked here more :-/). Well even though this new one is still 250Ω, the treble is MUCH more forgiving. I can't say if the pads are solely to blame for this or if it's something else inside, but I haven't had the mind to open up my new ones and take a look. If I did I'm sure I might find some other interesting things.
The other, less noticeable sonic difference that could probably be contributed mainly to the change in the velour pads is the bass. Unlike the 600Ω version that lessens this off and purportedly gives a more balanced overall cohesion with the rest of the audio spectrum, here we actually have MORE presence and more impact. It's a small difference, really, but it's there. For a lot of people that probably isn't good news, and of course if you have the amp to support it you should go with the higher impedance version as even Beyerdynamic themselves will tell you it's the superior version. But for whatever reason, should you end up with one of these newer 250Ω versions, either because it was gifted to you, or you don't feel confident in your amperage, or you're an idiot and didn't check the Head-Fi forums in like a year before deciding he wanted to replace his old messed-up pair (in which case you wouldn't be reading this warning anyway), then be prepared for some discrepancies between what you read in some older reviews and what you know about the DT990 and what you'll actually get in the latest batch of products coming off the assembly line.
On a side note, I noticed a lot less dependence on burn-in with this latest pair. The first two pairs absolutely needed it but this one hardly showed any difference afterward. I have no idea what I'm going to do with my old pair...
