It wasn't obvious from a quick scan of the manual whether there was any other form of lip sync or audio delay setting that would affect the built in speakers. Mind you that doesn't mean there isn't any. Some of the Samsung "e-manuals" I've seen have been as useful as a chocolate fire guard and tell you sod all useful.
So it might be worth looking in the Audio settings menu for any Lip Sync/Audio Delay setting for the speakers and giving it a try.
If it was only affecting external devices, such as the Blu Ray player, I would be looking in the menu systems on those devices for a Lip Sync/Audio Delay setting and tweaking that.