So here my updated impressions of the Shure pads vs. the Stock pads:
The most obvious difference I hear is that the Shure muffles the sound a bit, compared to the stock pads. This is because they use some sort of thin foam to cover the driver, instead of fabric or mesh. This does mean that if feels more comfortable on the ear compared to the stock pad. The way I tested this though is that I put the stock pad on my left ear and the Shure pad on my right ear and I could hear an obvious imbalance in the volume level (left being slightly louder, i.e. less filtered than the Shure pads).
Now on some closer listening, the highs seem to sound less natural and a bit more metallic. As if it's being diffused. To give you a better idea of what I mean, I was listening to the song 'What Do You Want From Me' by Pink Floyd (which I think is a well mastered recording and has a nice soundstage) and there is an almost constant hi-hat playing throughout the song. This hi-hat sounds nice and crisp and has a fairly short decay when I listen to it with the stock pads. But with the Shure pads it sounded slightly more diffuse, somehow metallic with slightly longer decay. It's almost like part of the sound wave is reflected off the foam driver cover back into the driver (but I'm merely speculating on this part), or bounces around for a few microseconds before it reaches your ear, since the drivers are angled. But whatever is actually happening, I don't like what it does to the sound. Highs don't sound as natural (well, at least hi-hats don't).
As for the bass, it's hard to tell. I think it's getting slightly more boomy, but I'm not completely sure. Kind of like the boominess of the cotton mod, which is very subtle, but there. But this too I need to give a closer listen.
Also the sound stage seems to get a bit wider with these Shure pads, but it also does something to the sound I can't quite put my finger on. Not sure if it's an improvement or a decrease in SQ, but will give it some more listening, probably tomorrow.
I might also consider removing the foam driver cover from the Shure pads and replace it with very thin fabric from an old hiking t-shirt I have. All I need is a scissor, thread and needle for that (which I all have :)) Will see about that after some further testing.
I'm also starting wonder now how the Shure 940 pads will sound (which are made of fabric, instead of the pleather on the 840 pads) with the 7520. Perhaps another thing that needs to be investigated :) Heck, maybe even the new Shure 1540 pads will fit this 7520 :P
Edited by starfly - 11/21/13 at 3:35pm