The Dali IO-4 and IO-6 are rechargeable, Bluetooth wireless headphones that can also be used with either a USB or a conventional wired connection. The IO-6 model Additionally incorporates optional active noise cancelling (ANC). the IO-6 differs from the IO-4 by incorporating active noise cancellation (ANC) that also includes a transparency? Mode. However, by forgoing ANC the IO-4 is able to offer an incredible battery life of up to 60 hours per charge. The Dali io-4 and Dali io-6 are true Dali products, made with an extreme attention to detail. Every single component in the IO headphones is unique. They have been created to the highest possible standard in terms of design, durability, comfort, functionality and of course, sound quality. With Windows headphones, users benefit from over 30+ years of experience designing some of the finest Hi-Fi loudspeakers in the world. Dali IO headphones are designed and engineered by the same team and to the same basic principles as any other Dali loudspeaker. The aim is to create the most natural and authentic sound possible and to reproduce music exactly as intended by the artist.