Supra-aural headphones—those that sit on the ear and create no seal around it—are easily the least popular type of headphone on the market these days. Yet some of the best-sounding pairs available, including most models made by headphone vet Grado, are of this design. The Sennheiser PX100s are incredibly lightweight, are comfortable, and push out some impressive low end. At high levels, your neighbors at work, or on a train or plane, will be able to hear your music, which is the main drawback of any "open" headphone design. The opposite is also true: You can hear your surroundings behind the music you're listening to. But if in-ear 'phones or bulkier, around-the-ear (circumaural) headphones aren't your thing, the PX100 set is terrific for the price.