Posts Tagged ArtDiffusor
You say “Diffuser,” I say “Diffusor”
Posted by Acoustics First in Diffusion, Q&A, Uncategorized on November 11, 2025
If you’ve spent any time around acoustic treatment—especially sound diffusion—you’ve probably noticed something odd: sometimes the product is called a “diffuser“, and other times it’s a “diffusor“. For newcomers, this can feel like a secret code or a subtle technical distinction – But the truth is much simpler.
Many trace the dual spelling back to Manfred Schroeder, the German physicist who developed the mathematically designed Quadratic Residue Diffusor (QRD).
In German, the word is spelled “Diffusor.” When Schroeder’s work entered the academic world, the spelling likely came with it.
Because his research became foundational in architectural acoustics, the German spelling spread through physics papers, textbooks, and graduate-level acoustics programs. Over time, “diffusor” became a common spelling when discussing mathematical or Schroeder-style diffusors specifically.
As manufacturers began producing these mathematically derived designs—like the ArtDiffusor® line from Acoustics First® (and many other early products)—they retained the “diffusor” spelling as a nod to the academic and scientific origins.
Before long, the industry ended up with two spellings that referred to the same thing:
- Diffuser – the standard English spelling
- Diffusor – the academically inherited, German-influenced spelling tied to Schroeder’s work
Both spellings appear throughout the professional audio world, and both are correct.
Is There Any Practical Difference?
No. None. Zero.
There is no technical difference between a “diffuser” and a “diffusor.” They both refer to devices used to redistribute sound energy and improve the acoustic quality of a space through accelerating the development of sound field diffusion. The spelling variation is purely linguistic.
Think of it like “colour” vs. “color” or “flavour” vs. “flavor.” British English keeps the “u,” American English drops it. (However, if you ask a Brit, they’ll tell you Americans are obviously spelling it wrong.)
The “diffusor/diffuser” split works the same way—just with a German twist.
So Which Should You Use?
Use whichever feels natural or matches the context you’re writing in. Many engineers and academics use “diffusor” when referring to Schroeder-type or other mathematical designs, simply out of tradition. Others stick with the standard English “diffuser.”
Tomato. Tom-ah-to.
Eight very different 2′ x 2′ sound diffusers.
Posted by Acoustics First in Diffusion, Product Applications, Products, Recording Facilities on June 30, 2025
Acoustics First® has maximized the idea of adaptable designs. One of the most common modular architectural elements is the 2′ x 2′ ceiling grid. While standard, fiber ceiling tiles have their uses, specialized acoustic environments require higher-performing materials – for both absorption and diffusion. While Acoustics First® excels with its Sonora® and Cloudscape® Ceiling tiles, today we are going to focus on the wide range of 2’x 2′ diffusers that have been developed over the several decades.
Sound diffusers in a 2′ x 2′ format have several advantages, other than just being placed in a ceiling grid to help diffuse the ceiling. They integrate well on walls and in arrays, where they can help break up large flat surfaces and help minimize flutter and standing waves from parallel surfaces. While they provide many different aesthetic options, there are also many different functional types of diffusers available in this form-factor to address different acoustic issues, from flutter, bass issues, targeted frequency absorption, and geometric scattering. Let’s look at some of these devices and their uses.
Geometric Diffusers.
Geometric diffusers have been around a long time. These devices break up large flat surfaces and redirect or “scatter” those reflections in different directions. They work great in environments where you need to redirect acoustic energy in a predictable way, and redistribute a specular reflection over a wider area. In a 2′ x 2′ size, you can also get a fair amount of bass absorption, due to the large cavity behind the geometric shapes creating a space that can be stuffed with absorbent material to tune it.
Quadratic/Mathematic Diffusers
Mathematic diffusers are devices that use specific calculations to design their size, shape, and structures to effect their performance. A common type is called the Quadratic Residue Diffuser (sometimes called a Schroeder Diffuser, after its pioneering inventor, Manfred Schroeder). This type uses a Quadratic Residue Sequence that optimizes uniform sound diffusion at specific design frequencies. There are different ways to implement these designs, but two common designations are based on their diffusion patters – 1D or 2D. A 1D Quadratic diffuser mostly spreads energy in one plane, and a 2D provides a hemispheric pattern.
Organic Diffusers.
Organic diffusers are a variation on the classic mathematic diffusers which use different mathematic functions to optimize the diffusion further by creating a smooth transition. Once such method is called Bicubic Interpolation. Instead of having the math restricted to having blocks at certain heights, the interpolation bridges these heights using a function that provides a smooth transition to the next target height. This transition creates unlimited resolution in the frequencies within it’s functional range, providing expanded uniformity throughout its range, and increasing its capabilities. As different frequencies are affected differently depending on their wavelength – the organic diffusers have no hard edges to define their pattern and look differently to different frequencies and energy from varied sources.
These diffusers all have the ability to be used in different types of installations for different reasons. Many of these diffusers are mixed and matched in the same room. You will see these on the walls or ceiling, and placed in different locations. There are rooms with Double-Duty diffusers for low frequency control, Model C for Mids, and Model F for flutter, while other rooms may have Aeolians™ on the rear wall and Model C’s and Model F’s to control the ceiling.
Keep in mind, these aren’t even all the diffusers we have available, these are just the ones specific to the 2′ x 2′ format. The Aeolian™ has a 1′ x 1′ version called the Aeolian™ Mini. There are flat panel diffusers that are hybrid absorbers and diffuser like the HiPer Panel® and the HiPer Panel® Impact. There are even large format versions of the Double Duty™ diffuser, Pyramidal, and even the Quadratic Diffuser.
For more info about these diffusers, read some of our, “Similar, Yet Different Series,” where we go into more detail about our products… and how some of these are similar, yet different!”
If you have any questions as to which products you need to optimize your space, reach out to Acoustics First® and we can help you find which products will be best for your application. Remember that Acoustics First’s® full line of sound diffusers are all made in the USA, with many available in stock for quick shipping.
Similar, Yet Different: Model C vs. Model D!
Posted by Acoustics First in Diffusion, Home Entertainment, Home Theater, Media Room, Multipurpose Rooms, Music Rehearsal Spaces, Music Tracking Room, Product Applications, Products, Recording Facilities, Recording Studio, Studio Control Room, Theater on January 5, 2024
In this installment of “Similar, Yet Different,” we take a good look at two very different looking diffusers in the 2’x2′ size… the classic ArtDiffusor® Model C and the organic, rippled ArtDiffusor® Model D – while there are some similarities, there are some key differences in how they look (obviously) and how they perform.
Quick Similarities.
The ArtDiffusor® Model C and Model D are both 2’x2′ diffusers which are made to be either wall mounted or installed in a standard drop-tile ceiling grid. They are both formed from a Class A fire-rated polymer in a single piece. Both are mathematical diffusers, which create their different physical features in a “form follows function” methodology. They also cover roughly the same frequency bands, with some minor variation in how they execute their control.
Difference in Math
The Model C is an interesting configuration. Often you will see quadratic residue diffusers with flat blocks or wells in a relatively standard quadratic cell formula configuration. The Model C runs in a much different alternating binary configuration. The basic idea is that cells are placed in a 45° array with each cell adjacency calculated as an alternating array of higher and lower cells starting in the middle and working in a pattern of alternating low/high cell clusters decreasing toward the edges of the diffuser. These diffusers also do not have flat tops on the blocks – they are angled at 10°. The orientation is then rotated in 90° steps in a pattern that maximizes the spatial redistribution of reflected sound. This was a vast design departure over the original quadratic design, and created a diffusion profile that was distinctly different.
The Model D was an even greater departure. It began with a Maximum Length Sequence (MLS) concept that first changed the varied straight channels into rings of different dimensions. These rings then broke from the MLS mold by getting varied height profiles based on the QRD sequence. As if having different size rings at different heights wasn’t enough… the randomness was further perpetuated through a Boolean process of assigning certain rings a random property that would either add or subtract height from any other ring that they crossed. Finally, the entire surface geometry was smoothed using a bicubic interpolation, creating the organic undulating surface which gracefully spans the entire profile.
What this difference in math does to the acoustic performance.
The Model C has a nice even diffusion profile through it’s primary working range. This is a product of the QRD design and binary distribution. The set size for the blocks guarantees a solid primary frequency range from about 1KHz to over 4Khz. This tunes the Model C squarely in the most sensitive bands of the human hearing range. Below this range the device becomes a bit of an absorber. Above this range and the performance becomes more effective at intervals, which can be seen in the areas of wide diffusion at 6KHz – 18 KHz. These repeating zones are common in “stepped” quadratic designs. Due to the heights of the well being at specific intervals, the intervals repeat at octaves of their effective bands.
The Model D doesn’t have the same stepping. The spline interpolation and the random Boolean shifts smooth the transition from one quadratic height to the next, and the MLS sequence causes a bit of a high-pass filter pushing the start of the primary range to around 2KHz – which is a little higher than the Model C. The main difference is that once the Model D starts it’s range it diffuses everything up to and over 20KHz without the banding that can happen in other quadratic designs.
Another difference in symmetry.
The ArtDiffusor® Model C is a fairly symmetric design, but it’s 45° angle pushes that symmetry along the diagonal (corner to corner) across the unit. The asymmetry is subtle but allows for enough variation to account for any “lobing” issues that can occur in more simple geometric devices The 10° block faces being at varied orientations is key to increasing the spatial directivity over the older “flat-faced” Quadratics. This was a very novel design when it was first introduced, and those benefits are crucial to the longevity of the Model C’s reign – It just works. It’s predictable and musical… and that’s why it’s here to stay!
The ArtDiffusor® Model D is a completely different animal from the Model C when it comes to symmetry… as a matter of fact… there isn’t really much on it that is symmetric! The Model D was designed as a departure from symmetry. Focusing on the mid to high frequencies, which are very specular, the organic geometry creates an asymmetric reflection pattern. This pattern can be used to steer the sound into a wider field.. and that profile changes with the wavelength of the sound that hits it. This steering ability and the wide frequency range has made the Model D a favorite in mixing and mastering environments, where they can get smooth performance through the entire frequency spectrum.
How these differences benefit everyone.
We have stated before that there isn’t really a one-size-fits-all solution in acoustics. Many environments will use various treatments to achieve their desired goals. You will often have different devices to address different problems, in different frequencies, in different locations, in the same space. Bass traps for controlling the lows. Absorption to reduce gross energy across the board. Large geometric surfaces to break up parallel reflections and steer the projection of sources. Mid range diffusers to create clarity to the sources and reduce artifacts. High frequency diffusers to reduce flutter and add a feeling of envelopment and airiness in the space. These devices all have their place – from the smaller listening rooms, to critical listening environments, and large multifunction spaces and venues.
It is also worth noting that these two devices have a very different aesthetic visually. The classic blocks of the Model C have become a signature look for quality sound environments, and people recognize them as they would classic geometric pyramids and barrels. The Model D aesthetic provides a visual accent that people take advantage of to set their space apart from others. The undulating, asymmetric pattern changes drastically when you rotate the individual units in the array. This allows for not only varied acoustic performance, but also a unique visual possibilities – with numerous variations.
The ArtDiffusor® Model C and Model D are two tools that are used to craft ideal listening environments around the world… and in those roles they are indeed Similar, Yet Different.
Similar, yet different: Quadratic vs. Itself?
Posted by Acoustics First in Diffusion, Product Applications, Products on July 6, 2023
For this installment of “Similar, yet different,” we will take a classic welled-quadratic sound diffuser, The Model Q, and compare its performance to itself – only installed backwards!
Taking “similar” to the extreme in this case, we are testing the difference in performance of a 1-dimensional, welled-quadratic diffuser installed in the standard welled configuration, and then installed reversed – with the sound impeding on the back side of the wells. For a bit of history, the Classic Quadratic Diffuser (or Schroeder diffuser) was designed with a grid separating the reflectors – creating wells of different depths proportional to the remainders of n2 (mod N). This design has some interesting facets.
- They are inherently symmetric if left in the original sequence.
- They are periodic (i.e. they repeat.)
- The discrete Fourier transform of the exponentiated sequence has constant magnitude.
The design principal is simple if you tear apart the math, and it’s simply wells that have a different effect on different frequencies, depending on the geometry of the wells. The Model Q is an advanced 1D-Quadratic with angled well-bottoms, which assist in smoothing out the performance and widening the 1D polar radiation. So if this design is relying on the wells to be effective, why would we reverse it?
An acoustically diffuse environment develops due to many factors, and while the frequency focus of the wells is useful, there are other scenarios where different methods may be preferred. If the geometry of the elements were flipped around, you would get the same (albeit reversed) ratio of distance, but you lose the containment and channeling that the wells provide. This imparts a diffraction on the unrestrained elements. This also allows for a different interaction between the elements, as the face of the unit is no longer planar.
Let’s look at the effect this has on the performance of the device at some different frequencies – starting low and moving up…
First, we will look at the 1150Hz performance of the devices… standard welled-install on the left, reversed on the right.
At 1150Hz, there is a little variation in the performance. Both are front focused, with a strong 1D horizontal polar response, but they are not identical. The welled-design (left) shows a broad frontal response, while the reversed design has a smoother vertical response, sharper front lobes, and stronger side performance. Overall, this difference is relatively small at this frequency.
Now, we will look at 2300Hz.
Again, we have two similar looking balloons, but there seems to be a bit more variation. The welled-design (left) shows a smoother 1D pattern in the front as the wells release sound within the same plane – at the front face of the wells. On the right you will notice sharper and more discreet lobes, but you will also notice that it has wider horizontal performance again, as it isn’t as front focused due to its free standing elements. The vertical performance is also a bit different – the welled design is broad and smoother vertically, while the reversed installation shows sharp lobes again.
Step up to 2800Hz, and we see some more drastic differences.
The performance of the standard welled-install (left) stays smooth and front-focused, while the lobes of the reversed install (right) have become even more distinct. Interestingly, the side lobes are even larger, showing an even wider polar pattern than before. These two instances show a marked difference between the smooth front-focused wells and the wide sharp scattering of the unrestrained elements. These two configurations are both very different, but are still both very effective at helping to disperse the incoming energy. Remember that the room develops diffusion through sound travelling in many different directions – these are not simple reflectors sending the specular energy in a single direction.
Now at 3650Hz we see a shift toward the reverse installation.
At around 4K the welled-installation (left) begins to move back front and center. It’s primary method of diffusion uses the wells to channel the energy, and at higher frequencies sound becomes much more directional. This directionality is used to create a temporal shift in the sound, as the reflections will occur out of phase from the source, and controlling that reflection is paramount to tuning this method of diffusion. However, as stated before, there are other mechanisms contribute to diffusion. The unrestrained elements on the right balloon, have hit their stride and still maintain a wide 1D polar pattern. The lobes are still sharp, showing the interaction of the elements with sound. This installation is showing the strength of its spatial dispersion, which will send acoustic energy in more directions and use the travel through the space to create a diffuse environment. It loses some of the frequency tuning of the wells, but makes up for it in the wide polar pattern.
Now for the super high frequencies – we jump straight to 10Khz.
This final set shows two diffusers pushed to the limits. The welled-installation (left) is a very narrow focused beam now. You will note that it has some variance due to the interactions with the walls of the wells but all of its work is done through phase shifting at this point. In contrast, the exposed elements (right) are still allowing for a bit of diffraction to occur, and the angled faces are still allowing for a bit of spatial redirection. Also note that these polar patterns were generated with a sound source directly in front of the device at 0° incidence, and the exposed elements would offer more exposure to its surface area than a welled design at wider angles of incidence.
In summary…
Diffusion develops using many different variables, including the untreated walls of the space. While both of these installations are functioning in nearly identical frequency ranges due to their geometry, the mechanisms which they work are slightly different and have different strengths. The welled-design (in classic temporal Schroeder configuration) uses the wells to channel sound and address the frequencies in a tuned and controlled fashion. By simply flipping the device around, however, you change its performance from a controlled time shift, to an unrestrained spatial redirector, which imparts time shift through dispersion, diffraction, and distance travelled – further reducing intensity by having a wide 1D diffusion polar pattern. Both have scenarios which one configuration would be preferable over the other, making the Model Q diffuser a very versatile device.
Both configurations are literally two sides of the same coin… they work in different ways, over the same frequencies, providing results – no matter how you flip them.
ArtDiffusor® Model D vs. Aeolian®: Similar, yet different.
Posted by Acoustics First in Diffusion, Product Applications, Products, Uncategorized on November 12, 2020
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 D vs. The Aeolian®. These two diffusers have some very interesting similarities and some surprising differences – so lets get started!
We have discussed the Aeolian® construction before, so we will start here with a quick recap as a reference point. The Aeolian® started life as a blocky-looking diffuser – just like the Model C, but the implementation is different. While the Model C retains its “blocky” appearance, the Aeolian® has run through a mathematical process called “bicubic interpolation.” This smooths the transition from one block to the next, creating the wavy appearance of the Aeolian® 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 the Aeolian®.
The Art Diffusor® Model D has multiple layers of math below its curved surface. While the Aeolian® started life as “Blocks” of different heights… the Model D started life as “Rings” of different sizes and heights. The calculation for the heights is identical to the mathematics used in tuning the Aeolian®, 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…
The Model D started 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 the Model D… look at the ripples in the rings.
This method of using Boolean Functions inserts a 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 the Aeolian®.
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… The Aeolian® looks a bit like rolling waves, and the Model D resembles droplets of rain in a puddle…
They do perform quite a bit differently though.
The Aeolian® has great lower mid-band performance… while the Model D is a beast in the upper mid-bands starting about 2.5K. The difference is in the severity of the geometry. The Aeolian® is a gently rolling surface which redirects the waveforms uniformly through a wide range of frequencies. The Model D has 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.
The Aeolian® is also deeper than the Model D – and this depth is a single resonant cavity… allowing it to be a great bass absorber as well. The Model D is 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 the ArtDiffusor® Model D and the Aeolian® 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.
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