As reported by JC Etter: 

On Boom, the alarm function defaults to the loudspeakers even when earphones are connected to the jack. This way you can fall asleep listening to music or radio, and hear the alarm in the morning.
On Babyboom, the jack has conveniently been moved to an accessible location on the side (had given Robin the fbk at the time Boom came out), but the jack switching feature has apparently been abandoned, making it unusable as a bedside alarm clock.