To improve the sound quality on Fitbit Flyer, use the power boost setting and adjust the fit of the headphones.
Power boost is an optional setting that enhances the sound quality of your music with added bass and equalization. Turn power boost on or off by briefly pressing the Up and Down buttons at the same time. You’ll hear an audio notification telling you if power boost is turned on or off. Flyer uses this power boost setting until you change it again. Turning power boost off helps conserve battery power.