At CanJam @ RMAF 2012, Sony's Naotaka Tsunoda brought both the Sony MDR-7520 (left) and the MDR-Z1000, so that I could compare them both, as I'd initially thought both were the exact same headphone, just in slightly different liveries--they're not. They do sound different, my preference being for the MDR-7520, with its more impactful bass and better imaging. You can see in the photo that there's one outside obvious difference (other than color) in the cloth coverings of the drivers (the MDR-7520's being much more sheer). There are also differences inside that result in each having its own character.