One of the best features of the MEX-BT5100 is the way it manages to integrate phone and music functionality into the same device while keeping the controls so simple. For audio sources, the stereo supports AM/FM radio, regular Red Book CDs, MP3, WMA, and ATRAC-encoded discs, and external sources via a rear-mounted auxiliary input. Those wanting to branch out can also invest in add-on modules for iPods and HD and satellite radio. When playing MP3 discs, the monochrome display can be configured to display a whole host of information including folder and track information, and tags for song, track, and artist information. While we like the ability of the system to display ID3 tag information, we are less impressed with the navigability of digital audio files, as there is no way to browse folder/song/artist information other than skipping through files one at a time. In partial mitigation of this, a one-touch shuffle function lets drivers play back discs in random mode. Like its predecessor, the MEX-BT5100 also comes with the ability to play audio streamed by the A2DP Bluetooth protocol.
All audio plays out through the system's built-in amp producing four channel's worth of 17 watts (RMS) output. Base sound quality is adequate (if a little flat), but it can be enhanced with a number of audio-tweaking functions. These include a three-band equalizer with six presets and a customizable EQ setting, a low-pass filter for customizing low-end crossover, and Sony's Dynamic Stage Organizer (DSO) function, which throws farther up into the car's cabin. The DSO function works particularly well for compressed audio formats, giving the audio a fuller, richer sound. For those who want to add their own external audio components, the MEX-BT5100 features a volume control for a separate subwoofer as well as three preouts for external amps.
With a price tag of around $330, the MEX-BT5100 is not cheap for a single-DIN car stereo. Its integrated Bluetooth hands-free calling interface, however, makes it more than a simple audio receiver, and for those looking for a good-looking, intuitive all-in-one entertainment and communications device, the MEX-BT5100 provides a compelling option.