I have read these books and documents:

1. QRDude user manual

2. F. Alton Everest- Studio construction on a budget

3. F. Alton Everest - Master handbook of Acoustics

4. Rod Gervais - Home Recording Studio: Build it like the Pros

5. Mitch Gallagher - Acoustic Design for the Home Studio

In the Master Handbook of Acoustics, p. 265; Studio Construction on a Budget, p. 160ff.

For example:

RPG QRD 734: N=7 , well width=3.4 inches; depth = 9"

RPG QRD 725: N=7 , well width=2.5 inches; depth = 16"

RPG QRD 1925: N=19 , well width=2.5 inches; depth = 16"

RPG QRD 1911: N=19, well width=1.1 inches; (depth not stated)

RPG QRD 4311: N=43, well width=1.1 inches; (depth not stated)

The author states that the fins are 0.5" in width.

__Questions:__

1. If the fins are supposed to be thin, why use 1/2 inch ones? Masonite or paneling comes in 1/4" thickness. **Why not use the 1/4" one instead?**

2. Based on the RPG QRD examples above, you could put any of these numbers into QRDude software and calculate the parameters for your QRD.

Given that each QRD has a different frequency range of diffusion based on the parameters, and according to the author, the 1911 and 4311 are used together (p. 266), **how do you know which of the above example numbers** (if they're used by RPG, then they must be the "ones" to use, after all, Dr. D'Antonio created the QRD based Dr. Schroeder's mathematics)?

or, in answering my own question, is it because the limitation of the well depth allowed by how much you want the QRD to extend into the room, will determine which of the N's and well widths that you can use?

Thanks.