Today on, “Similar, yet different…” we are going to analyze two more of our acoustic diffusers and compare/contrast their designs and functionality… and this one is a doozy;The Model Dvs.The Aeolian®. These two diffusers have some very interesting similarities and some surprising differences – so lets get started!

Aeolian® Sound Diffuser

We have discussed the Aeolian® construction before, so we will start here with a quick recap as a reference point. TheAeolian®started life as a blocky-looking diffuser – just like theModel C, but the implementation is different. While theModel Cretains its “blocky” appearance, theAeolian®has run through a mathematical process called “bicubic interpolation.” This smooths the transition from one block to the next, creating the wavy appearance of theAeolian® diffuser.

So, keep that in mind: The diffuser was tuned with different height blocks and then the transitions were smoothed.

Look at the smooth curves of theAeolian®.

ArtDiffuser® Model D

TheArt Diffusor® Model Dhas multiple layers of math below its curved surface. While theAeolian®started life as “Blocks” of different heights… theModel Dstarted life as “Rings” of different sizes and heights. The calculation for the heights is identical to the mathematics used in tuning theAeolian®, but why different sized rings?

There is an older diffuser design known as a Maximum Length Sequence (MLS) diffuser. These were tuned to different frequencies using a specific depth, and different spacings of “lands and valleys.”

MLS Diffusers had same depth wells of different sizes and spacings…

TheModel Dstarted with the concept of twisting the MLS spacings into rings, and changing the size of the rings. Then to break the “MLS mold” of having the same depth, this MLS ring structure is raised to different heights using Quadratic Residue calculations… effectively combining the rings of MLS spacings with different QRD heights. While this could have been where this stopped, we wanted to interject more randomness into the equation.

Wherever the rings of different heights intersected, we decided to change the heights by values relative to the difference between the two rings. This height variation is what is responsible for the “random” waviness. This was accomplished with different Boolean Functions, to either add or subtract height where the rings intersected.

You can really see the variation in the geometry of theModel D… look at the ripples in the rings.

这种方法使用布尔函数插入一个known-height randomization into a hybrid MLS/Quadratic system. (That’s a mouthful.) The final step, after refining the ring size, height, position and intersection parameters… was to smooth the whole geometry with “Bicubic Interpolation.” That’s right. This final step smooths all the transitions from the heights, just like the blocks of theAeolian®.

So onto the Simple Similarities!

Both diffusers use a quadratic residue calculations to get the main heights of the diffusive elements. Both diffusers are finished off with a helping of “Bicubic Interpolation” to smooth it all out. This gives them both a very organic look… TheAeolian®looks a bit like rolling waves, and theModel Dresembles droplets of rain in a puddle…

They do perform quite a bit differently though.

TheAeolian®has great lower mid-band performance… while theModel Dis a beast in the upper mid-bands starting about 2.5K. The difference is in the severity of the geometry. TheAeolian®is a gently rolling surface which redirects the waveforms uniformly through a wide range of frequencies. TheModel Dhas a very irregular surface. With the different ring sizes, heights, locations and boolean functions… it’s meant to target and shred mid to high frequencies. Both diffusers are asymmetric – and affect different frequencies in different ways.

TheAeolian®is also deeper than theModel D– and this depth is a single resonant cavity… allowing it to be a great bass absorber as well. TheModel Dis useful in environments where you have bass control in place, but really need to diffuse the upper mid range and bring those frequencies to life… or maybe shred some flutter echos or comb filtering. There are scenarios where both are used in the same environment – but for different reasons.

In Conclusion...

While both theArtDiffusor® Model Dand theAeolian®both look like liquids frozen in time, they have some other similarities in the math behind them… Yet they are still as different as rolling waves versus droplets of rain in a puddle.