There is an obscure feature of Quicktime that has been a hidden part of its interface for years, but I imagine it might be unknown to some users. I'm speaking of the ability to crank up the volume beyond the normal maximum.

The volume slider on the left of the Quicktime UI, as you might expect, allows you to adjust the volume of the item in question by sliding up or down. If you hold down the Shift key, though, you can crank the volume well beyond the normal maximum.

I'm resisting the urge to fit in a This is Spinal Tap reference here because, based on the position of the slider when the Shift key is held down, the volume doesn't just go "one louder," it goes another 20 louder.

Insert hearing damage warning here.