Speakers should be situated to provide good, even coverage to the audience with minimum obstruction. When stacking a speaker system, make sure the deck is solid and level. Often a scaffold that appears to be solid and level sinks or bends with the concentrated weight of a speaker system, causing the speaker stack to lean. The scaffolding should be inspected before, during, and after stacking to ensure safety. Speaker stacks for outdoor concerts must be secured so that they cannot blow over. Sub-low cabinets should be stacked directly on the floor so that the cabinet can couple with the ground. Other speaker cabinets should be above head height so that the sound from the cabinets can disperse.