Modern TV's are thinner than ever and as such have to make their speakers thinner too
TV manufacturers have to compensate with the sound, by adding a processed sound, this is created by adding a delay between speakers built inside
If you encounter a delayed microphone sound try changing the audio input on the "TV to Standard Mode" or "Music Mode"
If you still encounter a delayed microphone sound, connect to external speakers or sound bar and the delayed sound will no longer be a problem. PC speakers 2.1 or small amplified speakers are great with singing and give a better sound quality than TV speakers