First i was very disappointed with the sound of this headphones, even my UE MetroFi 220 of 20£ are much better. Then i did some burn-in but no significant changes, i was really thinking that i wasted my money in a headphones that the sound are so weak, no bass. When i found some guys doing a mod to this, called "bass mod", well thats what i did too to see if it could be worth the money it cost. I opened the cans i did 5 holes with drill in each can. I tested again and WOW that was a hell of difference, now the sound is much more powerful, more enjoyable.