Better or louder ? If you mean louder let's take a look at it.
Speakerwise spl is affected by two major things. Cone area and power. So lets say the power will be equal and the deciding factor is cone area.
This is pretty simple to figure out. 3.14x the radius squared. So lets see. I don't have these subs laying around to actually measure so I will have to guess at a couple of things.
2 15's - Taking away the mounting ring and the surround usually leaves a diameter of about 13". so I'll use that number for the equation.
So that means the radius would be 7.5" ( half of the diameter). So multiply 7.5x7.5=56.25. So now multiply 56.25x3.14 =176.625. So each 15 has 176.625"^2 surface area. Now multiply 176.625x2 (for the two subs) = 353.25"^2 So the two fifteens would have a surface area of 353.25"^2.
3 12"s Taking away the mounting ring and the surround usually leaves a diameter of about 10". So I'll use this number for the equation. So that means the radius would be 5". using the same formula 5X5=25, 25x3.14=78.5. So each 12 has a surface area of 78.5"^2. Now multiply 78.5x3(number of subs) = 235.5"^2. So the three twelves would have a total surface area of 235.5"^2.
So now let's look at the numbers
2 -15's with 353.25"^2 of surface area
versus
3-12's with 235.5"2 of surface area.
The three 12's would look to be the better choice. But in actuality the two 15's have the potential to be louder
Of course this is also dependant on the type and size of the enclosures, and the power. But if all of this is equal the two 15's would be louder.
[ 12-27-2001: Message edited by: ramos ]