The Beyer DT-220 are a very solid pair of headphones and excellent for serious mixing requirements. While the DT-100 are now the industry standard (and for good reason) I have no regrets buying 4 pairs of the DT-220 which I managed to pick up 2nd hand for £40 a pair. The range is good at 20-20,000 htz and the sound is fairly neutral,being neither  too bassy nor too trebbley. What you hear is what you get which makes these ideal for professional jobs. I have used these for day long sessions without suffering any ear fatigue which is essential...