When I first purchased them a month ago , I got a defective pair but they were immediately replaced by the seller. I still have the defective pair with me. I got the replacement three days after and to be honest, I was not impressed with the sound. The mids was too forward and the highs was kinda sibilant. The bass was just fine to my taste and I think that was the biggest asset of these earbuds. After that I just kept them and didnt listen again, but every time I burn in new acquitions I also burn in them. To my estimate they already have more than 200 hours of burn in period.
Last night, I tried them again and to my surprise they sounded amazing to my ears. The bass was really tight and controlled, hits really hard and can really go low. The mids is still forward but I like it now especially the vocals. I dont hear sibilance now and the soundstage is really great. I think they really need a long burn in period.