A bit of backstory from me:
I own both a DT770/Pro-80 and a DT990/Pro-250. I had the DT770 for a few years before I got the DT990. When I first got the DT990 I was not impressed. I didn't feel the bass was as good as my DT770, and the mids were too overwhelming. My DT990s sat unused for a few years while I continued to use the DT770s. At that point I was already on my 2nd set of velour pads and they too were pretty funked out. I decided to try a pair of clear gel earpads for my DT770. I initially felt like the gel pads were an improvement, but over time the things I didn't think would matter (like the gel pads being too sweaty) caused me to use the DT770s less and less. I started to use the DT990s again and they eventually became my main headphone to the point where I actually prefer using them over the DT770.
Since I recalled that I previously preferred the DT770 over the DT990 when comparing them head to head, I thought maybe the gel pads for the DT770s weren't as great as I originally thought. I ordered a pair of replacement pads labeled "EDT 770 V". I put them on the DT770s but in the end I still find that I now prefer the DT990.
Unfortunately this whole ordeal has produced nothing but confusion for me in terms of the pads, and if there are any differences between them.
When I originally had the DT770 and DT990 side by side 4+ years ago, I do recall there being clear and noticeable differences between the pads. My memory could just be foggy but I seem to recall one of the differences being that the DT770 pads didn't have air holes in the back of the velour pads that face the driver whereas the DT990 pads do. The pads definitely weren't identical.
The "EDT 770 V" pads I bought however indicate in the instructions that they can be used for the DT770, the DT990, as well as many other headphones - as if there is no difference in the pads and they are interchangeable?
I also noticed that these "EDT 770 V" pads have air holes in the back of the velour that faces the driver, just like my DT990 pads. Again I could be mistaken but I could have sworn the DT770 pads I had before the gels did NOT have air holes in the back of the velour. If they are indeed the same, i'll probably just put the fresh new pads I got for my DT770 on my DT990 instead - but the last thing I want to do is change the DT990's sound in a negative way.
Can anyone provide some clarification here? If the DT770 and DT990 use different pads (as I personally witnessed), then why are a single set of pads being sold as usable for both? Which type of pad is actually the correct pad for each type of headphone?