Open Sound Profiles and choose a preset, or set the 5-band EQ.
Your EQ settings also apply when you switch to W+ Link. More in the S11 EQ guide.
If it doesn't work
The LED doesn't flash fast. From off, hold the joystick for 4 seconds. From on, hold it to the right for 2 seconds.
It connects in the wrong mode. Double press the joystick. White is W+ Link, blue is Bluetooth.
S11 turned itself off. It switches off after 10 minutes without a connection. Turn it on and connect again.
It still won't pair. Clear the old pairings and start again. On S11, with the power on, hold the joystick to the right for about 10 seconds until the LED flashes 5 times. On X03, with the power off, hold the button for 8 seconds until the LED flashes 5 times.