Wireless headphones have progressed from being less-than-reliable Infra-red carrier system to the modern digital radio transmission types now produced by Sennheiser. The RS170 is the second model of this range, and offers excellent sound and the ability to listen to music from the source device regardless of where in the house you want to be. There is, of course, still the popular application of TV sound for those who like it turned up to levels the rest of the household finds s bit much! With a frequency respons of 18hz-21khz these are full-rnage devices. The RS180 will show improved clarity over the lower models.