Samsung UE40ES7000U E-Manual page 149

When sound is emitted from both the
main speaker and the audio receiver,
a sound echo may occur due to the
decoding speed difference between the
main speaker and the audio receiver. In
this case, use the TV Speaker function.
N
Audio Format
depending on the broadcast. 5.1ch
Dolby digital sound is only available
when connecting an external speaker
through an optical cable.
option may differ