quadratic diffuser

[debk]

In anticipation of building my Jagers, I just spent a few hours trying to understand the felt quadratic diffuser.  As I understand it, the inner pattern looks like a N19 pattern.  If I measure the cells I could calculate the frequencies it is designed for.  There are online calculators for this type of design.
I am baffled by the function and design of the outside part of felt. I would appreciate any help or references to understand the design

Thanks

Debra

[Doc B.]

It's been a few years now since I ran the math and I'm afraid I don't remember the frequency band or the calculator I used. The inside edge is a 2D diffuser pattern. The outside edge is a 3D diffuser pattern. I picked some of the cut felt out of the trash (the stuff smells like burnt hair) I was able to measure the steps at about 10mm. And that top layer is approx. 7 to 8mm thick.

[debk]

Thanks, the 2d pattern design is understandable.  I need to do a lot more reading to understand the 3d patterns.

For some strange reason I find this topic fascinating.

[Doc B.]

My terminology is bogus. The inside edge is 1D and the outside edge is 2D. Look for a copy of the Master Handbook of Acoustics. It covers quadratic diffusers and it's an excellent resource on room tuning. And of course there are online calculators like I used, and also apps. I probably have some hand scrawled notes somewhere but I have no idea where to start looking. Might be best to leave those to be found by the cleanup crew after I die.