Setting up a phase seven stack (5 soundstages, a four-tier rack and a reference top) shows that a 'finger tap' impulse on the top glass is transmitted down the stack and then is reflected back up it to the top again. Some of the energy will be dissipated as heat during this process. The four-tier rack in particular rings like a bell with a sustained note doing this.

Of course, a finger tap impulse on an empty rack isn't the same thing as a humming transformer in a box on a laden rack.

The reflection thing is interesting. I guess that each phase will transmit some energy down to the next in turn, but some will be reflected back upwards. The more phases you add, the more chance there is that the vibrations will be out of phase and cancel. I honestly don't know.

Some who know say that a Mana stand acts as an amplifier. The glass on spikes is probably responsible for this effect.