Ok, if I remember geometry right the area of a circle is pie r squared so the area for a 12" speaker is 113.04 giving me 226.08 square inches of area in a 2x12 cab. The area for a 10" speaker is 78.5 giving me 314 sqr inches in a 4x10. 226 goes in to 314 1.38 times so the 4x10 has about 38% more area moving air than a 2x12. First question, is that correct? Second question, does 38% more area mean 38% louder? I think I can simplify this question like this. If I have one 4ohm cab OR 2 8ohm cabs of the same type, is it now twice as loud? In other words, if I keep the wattage and ohms constant, does doubling surface area (by doubling the speakers) double the volume? I'm trying to figure out just HOW MUCH louder a 4x10 is than a 2x12! My answer is 38% louder. Any help out there on this?