Not sure if it's still true, but YouTube used to only support 2.1 audio output.
In that timeframe, my compatriots were not aware of this and several of them upgraded their home theaters to 5.1 or better.
For some reason, the myriad videos on YouTube claiming to help you test your 5.1 setup never seemed to get the results they wanted ...
My wife says the accelerated "tink tink" is her favorite part of Steve's videos (though she likes other parts, too).