These headphones offer excellent sound quality right out of the box, even without the 50 hours of burn-in required. Detailed mids and highs, punchy bass, but at times there is boomy bass. My ears got quite sweaty after about 5 hours of use with an iPod. Their overall quality (especially bass) reduced quite noticeably when used with a computer (They are optimized for the iPod). These sounded great with acoustic music from Jack Johnson, Rock and Heavy Metal Music from AC/DC and Metallica because of their ability to deliver excellent mids and highs...