For me the difference between the
I A/B'ed the XS and M-80 to see what differences I could hear when I received them on Saturday. I did hear a slight improvement in the treble in the XS relative to the M-80, enough to call out the difference but not enough to suggest that the drivers are different. The differences could be created in other ways (something like what Mr Speakers does with the Doggie Treat mod to the Alpha Dog), but exactly how I am not sure. I think V-MODA did the right thing by not altering the sound of the M-80 too much in going to the XS -- the XS' sound is different enough from the M-100 to give the XS it's own character.
That's correct that sound can change through other means - different cup housing material, the fill material and quantity, (and as demonstrated with the XL pads) the earpads too, not just the driver.
I'm guessing that you're probably not going to open your V-Modas. Are the XS pads the same as the M-80?