Difference in different pads or for example worn in and fresh pads can easily be measured. For example Crinacle provides some measured examples of this on his site. (Or Focal pad rolling in the headphones forum.)
Also a change in dampening materials or different dust covers can be measured with high precision testing equipment.
There are two big questions though:
- Can you hear the difference?
- Is the difference bigger than general variation between units/drivers?
Another note: Blind test is actually not easy because you can easily feel the difference of different pad-shapes/material/headbands.
@Resolve : I have listened to that interview and it was super interesting, thanks!
The old dust cover was there in early examples people posted ( I checked old pics on head-fi) and also in the original press release for the Ananda you can see it. My guess is that they changed it at about the time the Ananda-BT was introduced.