What's the truth behind a wall of Marshalls?

[usablefiber]

i was wondering that about yngwie: he has about 16 4x-12 cabs and heads on his stage for a big wall of speakers. i don’t know how he manages all that one stage unless some of them are dummies

 

[usablefiber]

i do know Ac/dc does actually use their wall of amps from the rig rundown where they have to bias and sound check each one for the gigs