Bluetooth audio is more than acceptable, however when the unit is in line mode (or USB / SD), a hissing suggests when there is no music, which is quite unpleasant. Apart from this detail the sound it comes out all confused mode is quite pleasant to listen to, there is no sizzle when listening to music at full power, bass are not extraordinary but sufficient.
In summary these speakers have a good price / quality ratio despite this little hissing problem (which can no longer be heard when the music is played)