As with pretty much all headsets, there are only minimal controls on offer. Alongside the multifunction call button there's also a mute button and a volume rocker switch that also doubles up as a track skip control. The buttons are very small and as a result are quite fiddly to use. For example, it's easy to end up increasing the volume level when you're actually trying to lower it. Another issue is that as you have to press the call button quite hard to activate it, you're also pushing the headset in towards your ear, which can be a tad uncomfortable.
We tested the headset with the O2 XDA Zest and although call quality was generally pretty good, the headset's boom mic does tend to pick up a fair amount of background noise. For example, when you're outside in slightly windy conditions the person you're calling will think you're wandering through a full blown gale. This is a tad disappointing as we would have expected more considering the headset includes Plantronics' AudioIQ noise-cancelling technology.
On the upside, music does sound great when you've got both earpieces attached. It produces meaty bass without sounding too boomy and its mid-range response is quite punchy. Overall, we'd describe it as very full-bodied and warm sounding.
Thankfully battery life isn't too shabby either. Plantronics claims that the headset is good for seven hours of talk-time and up to six hours of music listening. These figures rang pretty much true during our test period. We got six and a half hours of talk time and five hours for music listening, which is not too bad.
Charging is carried out via the microUSB socket on the rear and Plantronics includes a standard wall charger in the box. A full charge takes around three hours and during the charging period the LED glows red. Once this turns off you know it's fully charged. There's no dedicated battery indicator on the headset, but if you press and hold the call control and volume down buttons simultaneously for two seconds the LED will blink to indicate the current battery level. One blink means its two-thirds full, three blinks means it's between a third and two-thirds full and three blinks indicates less than a third of the battery life remains.
We wish the noise-cancelling technology was a bit better, but on the whole the Voyager 855 is a classy dual function headset with good all round performance. If you want a single headset for taking calls and listening to music, it's one of the best options around at the moment.