I've been listening to my Tennmak Pro's for about a week now, and I recently went back to my ZST's. They sound awful. I'll give the ZST's about 2-3 days of regular use and they'll be back to my favorite headphone. I'd suggest giving them about a week. They really are excellent. Your brain plays a lot of tricks and I'm beginning to think most of these IEM's eventually end up sounding almost exactly the same with enough time sitting in your ears while music plays. I've come to a conclusion that burn-in is a mental effect, rather than a physical change inside the actual IEM's.