LG CineBeam Laser 4K Owner's Manual page 138

Sound Problems
First of all, perform a
any abnormalities in the projector.
If you are using a set-top box, turn it off, and then turn it back on.
Make sure that the set-top box is correctly connected to your projector.
The screen is fine, but it does not play any sound.
•
If you use a set-top box, there will be no sound if you have set the volume of
the set-top box or your projector to 0 or enabled Mute. Set the volume to an
appropriate level.
•
(Q. Settings)
Set the [Sound Out] to [Internal Projector Speaker] or [Internal Projector
Speaker + Optical], and then check it once again. If you can hear the sound just
fine, you need to set the external speakers connected such as a soundbar.
There is no sound coming from one of the speakers.
•
(Q. Settings)
Adjust the balance as necessary with the Navigation button in [Balance].
(Q. Settings)
[Sound] [Sound Out]
[Sound] [Sound Mode Settings]
[Sound] [Sound Test] to check for
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[Balance]