Difference b/w RPG Skyline and GIK QRD diffusors

Here's another alternative for you. The Alphasorb panel from www.acousticalsolutions.com. As I recall they are about 470.00 per pair delivered. These panels are not as visually challenged as other diffusors.

I can't comment on how they would compare with your other contenders. I will say that these are very powerful tools and 2 or 3 on the wall makes a profound difference. It is easy to over do it in a room my size. I own 4 panels and with my current setup only use 2 on my back wall.

GIK also has the D1 diffuser as well which would be a less costly option as well.

I was interested in the design of the skylines a few years ago. The actual mathematics is interesting and the design is NOT patentable.
Make your own for next to nothing compared to the overpriced panels made by them. The mathematical series is findable and translatable into a panel for the heights of the individual square pegs. Curiously, a BETTER idea is to have the squares in a variety of diameters, but that is just my notion, and the idea does not have any mathematical basis that I could locate. actually any shape will do, so rods can be just as effective.
Use the picture of the item and guesstimate the sizes and it WILL be 99% as effective. The lengths of the rods are a varying matematical equation, and the 'made' panels are just one of billions-plus of possible (equally good) particular height/shapes. So go for the home made ones, and hopefully RPG will learn not to sell very overpriced stuff. (The actual idea is NOT thiers anyway)

And PLEASE do not ask me for a link. I just read up on it years ago. The article that started my search was probably in a stereo mag... then some mathematical society journals.. Maybe some audio journals..
I SAW a mathematical series and the equation for the values.. and a discussion of the acoustical properties..

RPG Skyline diffuse in two directions, so you get a hemispheric soundfield around one of these, as opposed to the vertical OR horizontal diffusion, whereby you get a hemicilyndrical soundfield.

As Elizabeth mentioned, the math is publicly available, and you could make this yourself, maybe using wood of a square section close to the RPG section, and cut it to the required lenght. Is not difficult, but it will be time consuming as you'll need a lot of pieces. For the math you can check out the Master Handbook of Acoustics by Alton Everest (I've seen links online to the pdf version, but I do have the book), which is highly recommendable reading anyway if you are getting into acoustics.

Horacio