Design and features:These earphones have an integrated microphone and volume, music player function, and call connect/disconnect controls for use with paired Bluetooth devices. Additional features include the ability to connect to two Bluetooth devices at the same time, and support for Apple Siri and Google Assistant digital voice assistants when used with mobile devices that have those features. The free Jaybird app download for Apple or Android mobile devices can be used to provide tonal adjustments, to help locate lost the earphones if they are misplaced, and provides notification when firmware updates for the X4 become available. This model is claimed by the manufacturer to be water resistant and comes with four pairs of ear pieces in various types and sizes, three pairs of removable ear bowl supports in various sizes, a proprietary USB charging cable, removable cable shortening clips, a removable clothing clip, and a carrying pouch.
Sound quality: The X4 comes with a free app download that allows customization of its sound. The tone settings of the app do have a noticeable effect on the sound of these earphones, but our tests were done with the tone settings bypassed. We found the X4 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 slightly lean midrange with somewhat prominent bass. Bass (as in bass drums, bass guitars, stand-up bass, etc.) has good impact and goes deep, but is somewhat prominent and a bit boomy. The midrange (voices, guitars, horns, etc.) is slightly thin, hazy, and grainy. The treble (cymbals, the upper range of violins, etc.) is extended, but slightly smeared (sounds that should have a delicate shimmer sound blurred). This model does a good 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 somewhat open--sound-wise it almost seems like you don't have anything plugging up your ears.
Comfort: The X4 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. They stay in place with no problem but users may have to fiddle a bit to find the position that provides the best sound quality. The ear bowl supports make the ear pieces very stable even with vigorous head movement, but users with smaller ears may find that even though they can get them to stay in place the earbowl fit is very tight. The sound of the earphone connecting cable rubbing on clothing may be heard through the earphones.
