The Good: Sennheiser's flagship headphones have high-tech styling, extraordinary bass response, and an extremely comfortable design. The Bad: They're heavy and very pricey, not to mention ill suited for use with the iPod. The Bottom Line: The formidable Sennheiser HD 650 headphones are fit for a king--and have a price tag to prove it. We approached Sennheiser's top headphones, the HD 650, with high expectations, as word of mouth for the product has been overwhelmingly positive. The headphones certainly look the part; the HD 650s' luxurious feel, the thickly padded headband and ear cushions, and the titanium-silver finish leave no doubt--even before you hear them, you can tell these are very special headphones. The HD 650s are pretty big and moderately heavy (9 ounces), but they're extremely comfortable. We logged many, many hours of listening time and came away thoroughly impressed with their comfort. They retail for $550.\n \nThe headphones' drivers are hand-selected to ensure precise left\/right matching tolerances and feature computer-optimized neodymium magnet systems to minimize distortion. Their lightweight aluminum voice coils ensure accuracy and fast transient response. The HD 650s' 9-foot Y cable is user-replaceable, and that's a good thing because over the years, cables inevitably break. The cable is terminated with a 1\/4-inch plug, and a high-quality miniplug adapter is included.\n \nThe Sennheiser HD 650s are intended for home rather than portable listening--they're too big and bulky for on-the-go use. The headphones are also rather power hungry, so puny iPods and MP3 players won't supply enough juice to produce much volume. With that in mind, we conducted all of our auditions on a home-theater system. We first popped on the Master and Commander DVD to explore the limits of the HD 650s' home-theater prowess. The naval battles' cannon fire exchanges never came close to fazing the Sennheisers. Bass was fuller than that of any other headphone we've ever used, and the sound appeared to come from the other side of the room.\n \nThere's a sweetness to the HD 650s' open sound that flatters all sorts of music. The detail is all there, but the treble frequencies are more laid back than those of the ($500). Hard-rockin' tunes sounded a little tame over the HD 650s, and a switchover to the RS-2s pumped up the excitement factor on Neil Young's Ragged Glory CD--the enriched blasts of raucous energy from Young's guitar sounded more realistic over the RS-2s. But we had the opposite reaction when we played acoustic music, as the HD 650s let us feel more of the weight of Cyrus Chestnut's grand piano on his Revelation CD. The HD 650s' superclean sound encourages listening at a high volume, even at levels that would be painful with other headphones. The HD 650s' bass is bigger than that of the RS-2s, but the RS-2s' definition clarifies details lost to the HD 650s. We heard texture way down in the mix in the RS-2s; details such as the bass player sliding his fingers over the strings are harder to hear on the HD 650s.\n \nThe Grado RS-2 and the Sennheiser HD 650 are both reference-quality headphones, and we would be thrilled to live with either one, although they sound very different from one another. The HD 650s had a bit more style and a boomier sound, but you'll lose a little bit of sonic detail. Your purchase may ultimately boil down to what you'll be listening to.