The closed-back Performance 840 headphones with his focussed bass range, is geared towards the acoustics of modern club music. In the low frequency range he clearly expresses full sound and puts the beats in a nutshell. The Performance 840 is available as bundle with the SIRIUS Bluetooth Adpater. The ULTRASONE SIRIUS is an ultra-compact Bluetooth adapter that was developed specifically for the ULTRASONE Performance series of headphones. Its curved design is perfectly adapted to the shape of the headphones and can thus be integrated seamlessly. At just 12 grams, it is also hardly noticeable. Thanks to a bayonet fastening, the cable can be simply removed and the SIRIUS attached, quickly transforming the wired headphones into a Bluetooth model.