Difference b/w RPG Skyline and GIK QRD diffusors

Maril,

The term QRD means quadratic root diffusor and refers to the math behind the calculation of these. I understand the Skyline is a QRD, but I realize it's confusing when there are commercially available products called QRD, like the GIK you asked about. Sorry my thread was ambiguous.

Diffusion in 1st reflection points on the side walls and on the ceiling (likely another 1st reflection point), is not uncommon. I would still be interested in understanding why Rives recommended diffusion on the front wall.

Horacio

RPG does make QRD panels as well, but Skylines are NOT QRD design.
I will try to ask Rives about it.

Look on line. You can buy RPG skylines for A LOT less on line. Paint them yourself for next to nothing if you want colors. There is online discussion on how to do so. Just google it. - Jim

I did look on line and there seems to be very small to no discount on Skylines, more so on LP version, that I don't need.
If you could post a link, it would be much appreciated.

Maril555,
Out of curiosity,did you ask RIVES why they suggested the Skylines for the centre of the front wall, or would that feel like you were challenging their expertise?! RiVES typically recommends a hemi-cylindrical (polyfuser) diffuser for front wall centre, not Skylines . . .

Given than Skylines will on average diffuse 50% of specular reflections horizontally and 50% vertically, whereas QRD's or hemi-cyclindricals will diffuse 100% horizontally, I would expect that you'll hear less ASW (apparent source width) with a 2D (i.e.Skyline) than with a 1D (QRD/Hemi)diffuser. ASW is associated with a wider soundstage. Given the listening distance from your chair to the front wall and given the propogation loss of reflections making their way to the front wall afer colliding with side and rear walls, in reality I doubt you'd hear any significant difference between Skylines and QRD on the front wall. You will hear more of a difference contrasting diffusion with broadband absorption on the front wall . . .

If cost is a concern, then I'd recommend building a DIY Skyline (see my system pics) or a hemi-cylindrical, both of which I've build several of and will gladly share my 'learnings.' Building your own will allow you to easily outperform the performance of mass produced Skylines and QRDs; RPG Skylines with its 7" depth will diffuse effectively to about 1kHz (50% of 965Hz wavelength is 7"). Diffusion should be broadband enough to work effectively (meaning cell/well depth should be a significant fraction of the wavelength, normally 50%) to 300Hz requiring a depth of 22.6" and a sitting distance of about 135" (3X the wavelength). Would your room accommodate these diffusion dimensions or slightly more conservative versions thereof?

The hemi-diffusers are great specular diffusers worth considering which can have their concave interiors stuffed with fiberglass to act as a bass trap - a two-in-one produce hard enough for MF/HF diffusion and LF absorption.

Some things to think about . . .