JoshK said:If they are all the same size, they wouldn't be able to be used over the same range. OS has much less loading that say the LC or tractrix. This is because it isn't a horn.
JoshK said:I need to calculate it but it is going to be bigger than 16" at the mouth. I know this because the 16" mouth radius is what Dr. Geddes's Summas were that were used down to 900hz. The Horn Theory part 2 article in AudioXpress gave a formula for the effective loading Fc.