I have been looking for a quality, high-audio quality set of headphones for use with a wide variety of bluetooth sources, including my T-Mobile Dash, Windows XP, and MAC OS X based systems.Unfortunately, my S805 units didn't rise up the challenge. At first, I considered the source material and/or the source BT transmitter was to blame. However, exhaustive further testing showed that the upper-frequency response of these units just left a lot to be desired. The distortion sounded like digital noise, or the result of clipping of the dynamic range. However, even at low source volumes and amplitudes and headphone volumes and amplitudes the high frequencies just sound awful.