Nsgarch - I'm not sure that the foam is meant to be absorptive due to open pores. RPG paints its diffusors, and I would imagine that this clogs up the pores. RPG does state that "the solid expanded polystyrene core of the skyline provides useful low frequency absorption", but also states that "the large prime number design offers the acoustic industry's largest reflection number density". Unless you are trying to make an "abfusor", I think you are after a reflective surface but with multiple angles of incidence and reflection, and not overly concerned with absorption.
John - you are right, the combination of columns is not random, and I was just being lazy in describing this. RPG uses "advanced primitive root number theory to design the most powerful two dimensional omnidimensional diffusing surface in the acoustical industry". Are their any skilled mathematicians out their (equally skilled in normal communication) who can explain what primitive root number theory is? I don't know how the link I provided arranges the various columns, but it is not purely random, as can be noted by the distribution of various column heights (at the bottom of the page). My hope is that it came directly off a Skyline, but I have no way of knowing!
Anyhow, I've referred to the discussion of diffusors in F. Alton Everest's "Master Handbook of Acoustics", specifically the discussion of "reflection phase-grating diffusors", or which the Skyline seems like a variant. At the time of writing the 4th edition (2001), the book seems to prefer quadratic residue diffusors to primitive root diffusors, and notes that diffusors built with separators between wells are most effective. The skyline doesn't use seperators, nor do the popular Auralex TFusors, but the RPG Omnifusor does. I'm not sure which of the 3 design is actually best. The RPG products are more evenly 2D than the TFusor, which seems to have less 2D effectiveness, but the TFusors are certainly most affordable. Back to the point: it would be great to know if the DIY design on the link is the same as the Skyline. It certainly isn't purely random, and recipes are available in Everest's book for both quadratic residue diffusors (which are symmetrical) and primitive root diffusors (which are not symmetrical, like the skyline and the DIY design). That just leaves me saying "hmmmmm".
Regarding covering a diffusor with fabric, yes I've heard that this compromises its effectiveness too (e.g. on the Audio Asylum acoustics forum). But the way it was stated seemed like here-say. Can anyone point to a basis for or against covering (seemingly ugly) diffusors with acoustically tranparent fabric?
John - you are right, the combination of columns is not random, and I was just being lazy in describing this. RPG uses "advanced primitive root number theory to design the most powerful two dimensional omnidimensional diffusing surface in the acoustical industry". Are their any skilled mathematicians out their (equally skilled in normal communication) who can explain what primitive root number theory is? I don't know how the link I provided arranges the various columns, but it is not purely random, as can be noted by the distribution of various column heights (at the bottom of the page). My hope is that it came directly off a Skyline, but I have no way of knowing!
Anyhow, I've referred to the discussion of diffusors in F. Alton Everest's "Master Handbook of Acoustics", specifically the discussion of "reflection phase-grating diffusors", or which the Skyline seems like a variant. At the time of writing the 4th edition (2001), the book seems to prefer quadratic residue diffusors to primitive root diffusors, and notes that diffusors built with separators between wells are most effective. The skyline doesn't use seperators, nor do the popular Auralex TFusors, but the RPG Omnifusor does. I'm not sure which of the 3 design is actually best. The RPG products are more evenly 2D than the TFusor, which seems to have less 2D effectiveness, but the TFusors are certainly most affordable. Back to the point: it would be great to know if the DIY design on the link is the same as the Skyline. It certainly isn't purely random, and recipes are available in Everest's book for both quadratic residue diffusors (which are symmetrical) and primitive root diffusors (which are not symmetrical, like the skyline and the DIY design). That just leaves me saying "hmmmmm".
Regarding covering a diffusor with fabric, yes I've heard that this compromises its effectiveness too (e.g. on the Audio Asylum acoustics forum). But the way it was stated seemed like here-say. Can anyone point to a basis for or against covering (seemingly ugly) diffusors with acoustically tranparent fabric?