Since this thread was bumped, I want to say that this is spot on.I have no misunderstanding and I never said mass didn't matter. I said it was unnecessary. It is irrelevant for the purposes of getting the frequencies. Any belt you chose is essentially going to be the same--which makes mass a CONSTANT in those equations. If it will help you sleep at night, you can re-measure the span every time too. Never know when those case-mounted pulleys are going to change positions on you. Got to make sure, right?
When I buy a chicken from the grocer, I don't ask what it weighed with the head and feathers. There is no reason for 99% of Ducati owners to care what the actual raw tension figure is if you have a simpler measurement that is directly proportional. The other "variables" are statistically insignificant.
But by all means, show us. If the Gates belt is 5 grams heavier than the Bucci, crunch the numbers and tell us how we should only set a Gates belt to 109 Hz and the Bucci to 110.
It would take a whole hell of a lot of mass difference to make a belt change that much in frequency considering the span.
And if anyone doesn't have a smartphone and wants to build one for less than $100 check out this thread:
How to make your RTA with $100 dlls. - DIYMA Car Audio Forum
I tested it against a certified RTA and it was more than close enough.