with relation to whitestrat's point about speaker deflection, that is very true.
Instrument speakers are different from hi fi speakers, they have a wide and short magnetic cone, whilst hi-fi speakers have very long and narrow one.
in home stereo sound systems:
The magnetic field is long and even, consistent throughout the entire length of the cone's vibration, this makes for lower compression, higher clarity and consistency.
in guitar amp speakers:
THe magnetic field is short, so at high volumes, cones exit the intense center of the magnetic field, hence causing damping. This is the speaker cranking part, where you achieve a compressed tone that is naturally punchier and more impactful.
This which i can observe in my 15 watt peavey's speaker, I experimented with it personally when I read up on it. It is true, and my ears almost died, so it's impossible to crank a 412 at home really, you need a hall as stated before.