Acoustics First BLOG

For this installment of “Similar, yet different” we look at The ArtDiffuser® Model C and the Aeolian® Sound Diffuser.

While these two diffusers look very different, there are a fair amount of similarities between them.  Their physical size and depth allow them both to be great mid-frequency diffusers, but did you know that the Aeolian® started life as a blocky-looking diffuser – just like the Model C?  It’s true!

ArtDiffusor® Model C array on a hanging bass trap.

The mathematics behind the two diffusers is similar, but the implementation is different.  While the Model C retains its “blocky” appearance, the Aeolian has run through a mathematical process called “bicubic interpolation.”  Without turning this into a math-heavy post, if you take a “blocky” design like the Model C and run its geometry through bicubic interpolation, you get a “curvy” surface like the Aeolian® – It “smooths” the transition from one block to the next in a 3 dimensional matrix.

While they did not begin as identical geometries, they were similar in their height ratios – with the Aeolian® starting with fewer blocks in a more random distribution, and a slightly taller maximum height.  They both effect similar frequency ranges, with the Aeolian® going slightly lower and higher due to its depth and interpolated surface.  The pattern and type of the diffusion is also different because of the different geometries – the Model C has blocks, and the edges of those blocks introduce a great deal of edge “diffraction” – which is what happens when a wave interacts with an edge, or corner, of a surface. It bends and shears around the edge, which helps break up the continuity of the waveform, where the Aeolian® takes the approach of redirecting most of the energy off a randomized and continually-curved surface.

Aeolian® Diffuser array on the back wall of Big3 Studios.

It is important to note that the two are similar, yet different in their absorption numbers as well.  With the Aeolian® being deeper with a single large cavity, it provides a bit more absorption in the low frequencies than the Model C, which is a more rigid geometry containing smaller elements.  Depending on the space, this may be a useful addition to the diffusive properties.  While some spaces need the extra absorption, some are pretty well balanced already and are just looking to “sweeten” the sound a bit.

On the surface, they are both a nominal 2’x2′ square of thermoformed Class A plastic with lightly textured surface.  That is the extent of the visual similarities, and we cannot hide the aesthetic differences between the two devices. The ArtDiffusor® Model C is a “classic” diffuser.  Many have been looking at these for the better part of 3 decades now.  It’s a classic design at this point with no need for introduction – it is what the quintessential diffuser “looks” like.  In fact, when many people think of a diffuser – the Model C is what they visualize!  The Aeolian® is a modern rendition of the classic design. Using modern calculation techniques, we can now present the type of diffusion the Model C is famous for, in a different way.

While the two geometries look entirely different, and perform a bit differently, they have a common heritage as mathematical, 2-dimensional diffusers.  You could say that the Model C is the grandparent of the Aeolian®, and that pedigree has been passed on – having a similar foundation, but a different final interpretation.