They may come with a hefty price tag but these earphones reportedly take sound onto a new level. Denon's latest AH-C751 earphones cost ?150 but the "Metal Bullet" design uses ultra-rigid machined aluminum that does not resonate, unlike plastic housings used in less expensive products. Denon's "Acoustic Optimiser" balances the sound pressure before and behind the diaphragm to reportedly give greater dynamics and fast transient response. All the contacts are made of gold, as is the 3.5 mm plug. They come with three pairs of ear adapters, a 0.8 m extension cord and rigid travel case.