The 2 1/2 times rule drives me nuts. It was once an appropriate rule of thumb - decide how high a
proscenium opening should be for function and aesthetics and assume the high
trim should be 2 1/2 to 3 times as high. Now someone decides on a
stage roof height on a basis that has nothing to do with what will be on
stage, probably budget, and then sizes the
proscenium using the 2 1/2 rule - and that doesn't account for the difference between high
trim and roof height - usually 4 to 5 feet. Another stupid piece of lore that allows someone who really doesn't understand what goes on in a
stage to proclaim themselves an expert and argue for another bad building. There are so many 12 and 15
foot prosceniums out there because of this mistaken and misused factor, it's criminal. If your are planning for band or
orchestra or chorus, you need to be in the low to mid twenty feet range minimum. Period. Then determine what high
trim you can live with for drama use. For me it has to do with
orchestra shell towers and the basic
masking setting and being able to move those towers without catching the
masking. This also worked when the “golden rectangle” rule of width to height of
proscenium was applied. 48' wide opening gets a 30' high opening using this pleasing aspect ration, which would result in a respectable 75' high
trim. But clearly the misapplication of the 2 ½ times rule that results in 60' wide by 16' high letterbox prosceniums misses the boat. Many other considerations but this is a start.
