I hadn't thought of that! TBD.
The X5's speaker cover looks light years better than the X3's. I also suspect the shape of the "grill" may allow for marginally better sound quality- much like how some older Sennheiser headphones had foam in them, and you could take out the foam to make them sound like the higher-end model, since the drivers were the same between the two.
https://www.head-fi.org/threads/is-t....615531/page-2