Design and features:The BackBeat PRO 5100 has integrated microphones, and volume, music player, and call connect/disconnect controls for paired Bluetooth devices. Additional features include an automatic ear detection feature pauses music when one earphone is taken out of ear and resumes when it is put back in, and support for Apple Siri and Google Assistant digital voice assistants when used with Bluetooth devices that have those features. This model is claimed to be water resistant and comes with three pairs of ear bowl support ear pieces in various sizes, a USB charging cable, and a charging cradle/recharger battery/carrying case that the manufacturer claims can be used to recharge the earphone batteries up to 2 times between its own charges. The free Plantronics Backbeat app download for Apple and Android mobile devices can be used to customize the control functions, disable the automatic ear detection feature, update the earphones, and help locate the earphones if they are misplaced.
Sound quality: We found the BackBeat PRO 5100 delivers sound quality that falls in the Very Good range - it reproduces music and voice very well although it does have some noticeable sonic quirks. The overall sound can best be summarized as bassy with a thin, grainy midrange and strident treble. Bass (as in bass drums, bass guitars, stand-up bass, etc.) has good impact and goes deep, but is somewhat prominent and slightly boomy. The midrange (voices, guitars, horns, etc.) is somewhat thin, and a bit hazy and grainy. The treble (cymbals, the upper range of violins, etc.) is extended, but is somewhat prominent and smeared (sounds that should have a delicate shimmer sound blurred) and the upper treble is a bit sizzly (sounds that should have a delicate shimmer have a sound reminiscent of bacon frying). This model does a decent job of recovering the room ambience of a recording (the sense of the acoustic space in which the audio program that's being listened to was recorded). The sound also has a good sense of liveliness and is open--sound-wise it seems like you don't have anything plugging up your ears.
Comfort: The BackBeat PRO 5100 is a hybrid ear insert/ear bud design - the earpieces seal the ear canals but they don't insert into the ear canals as far as typical ear insert models, and they are supported by ear bowls like a ear bud model rather than the ear canals. Regardless of ear bowl size, users will probably find that they stay in place with no problem for casual use, and that the ear phones are very stable even during vigorous head movements.
