What dictates skyline diffusor frequencies?

[emptysetjeff]

I'm well into construction on my control and live rooms of a small home studio. My control room is much larger compared too my previous location. However I'm trying to understand the calculations for the various diffusor/absorbers.

I would like to know how to calculate the frequencies of a skyline diffusor for my back wall. Many online calculators have two frequencies to pick from yielding sometimes longer parts. But what really controls this? I would not rather not waste time/materials/money.

I believe it is based on your space, which I have below. I couldn't get the image link to work in this forum, but I think it is because of using google drive.

https://drive.google.com/file/d/11FOnay ... sp=sharing

Just wondering if anyone has some suggestions? I've downloaded John's spreadsheets and need to understand the connection. Maybe it is better to build a quadratic style instead?

Thank you and Happy New Year!