Archive for category Diffusion
Big vs. Bigger: 2′ vs 4′ Acoustic Diffusers
Posted by Acoustics First in Diffusion, Product Applications, Products on December 16, 2025
A couple common form factors in acoustics are based on building material sizes. Ceiling grids are a common place to install acoustic devices, and you will find that many are built to either work in a 2’x2′, 2’x4′, or 4’x4′ ceiling grid installation. This makes sense, but did you know that these devices also perform differently in some cases due to their dimensions? This is especially true with acoustic diffusers.
When you’re tuning a room—whether it’s a studio, theater, rehearsal space, or even a high-end listening room—acoustic diffusers are one of those rare tools that improve clarity without taking the life out of the space. Designs like the Double Duty Diffuser, Pyramidal Diffusers, and Quadratic Diffusers all share that same mission: redistribute sound energy so your room feels open, natural, and honest.
But while they may look similar in concept, their size changes the game. A 2’x2′ panel and a 4’x4′ panel both diffuse sound, but their effect—especially in the low-frequency and low-mid ranges—can be very different.
2’x2′ Diffusers — Compact Control
2’x2′ units are the most modular diffusers in the lineup. Their smaller footprint makes them ideal for:
- Breaking up mid and high-frequency reflections
- Treating small and medium rooms
- Sitting comfortably in grid ceilings or tight wall spaces
Because of their size, 2’x2′ diffusers don’t interact as much with the low-frequency energy in a room. Bass waves—being physically large—tend to wrap around smaller objects. The result? Excellent clarity improvements in the mids and highs, with a very predictable diffusion performance. The Double Duty Diffuser and Pyramidal diffusers have been a standard in breaking up planar surfaces for decades. While their diffusion in low frequencies is limited at this size, the air cavities do help control some upper bass frequencies through absorption.
The tuned mid frequency effects of the 2’x2′ quadratic, and the smooth performance of the Double Duty or Pyramidal diffuser are perfect for control rooms, edit rooms, drum booths, and anywhere you want accuracy without sacrificing sparkle.
4’x4′ Diffusers — Where Diffusion meets Bass Control
Now we get to the big ones.
A 4’x4′ diffuser is similar in concept to its smaller relatives, but the scale moves it into a different acoustic category. At this size, diffusers begin to influence longer wavelengths, which opens the door to something smaller diffusers often struggle with…
Low-frequency interaction
Large diffusers present enough depth, volume, and surface area to affect the bass spectrum. The extra size creates cavities which are tuned to reduce bass, and they have surfaces large enough to redirect those lower frequencies.
- Break up standing waves in the low-mid range
- Reduce modes and nodes common in rectangular rooms
- Add a sense of openness to the bass field
- Prevent buildup behind listening positions
In other words: same diffuser concept, very different low-end behavior.
Wide-area coverage
A single 4’x4′ panel can modify a huge portion of a wall, creating an even, spacious character that feels less like “treatment” and more like a room that’s naturally well-behaved.
These panels shine in larger studios, live rooms, and worship spaces—anywhere you need diffusion that reaches deeper into the frequency spectrum – and can break-up large, flat, specular surface reflections, which are responsible for flutter, echoes, bass buildup, and long reverb times.
Which do you need?
There are two main factors in the decision: space and performance requirements. In certain environments, it’s impractical or impossible to install large 4’x4′ or larger diffusers; It also may not be the best solution – even if it may appear to be on paper. While a single, large barrel diffuser may appear ideal, you may not have enough physical space to allow the diffusion to develop – where several smaller diffusers would be the better solution.
In short, your physical space and acoustic conditions will dictate which size elements will give you the most benefit in your environment.
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.
Similar, yet different: Angled QRD vs. Standard QRD
Posted by Acoustics First in Diffusion, Product Applications, Products on August 19, 2025
In this installment of “Similar, yet Different,” we explore the similarities and subtle differences between a classic, standard 1D QRD and a modern, angled 1D QRD. While being based on the same mathematic function for their design, there are a couple subtle differences in the performance of these devices.
Quick review. A Quadratic Residue Diffuser is based on a mathematic equation that states that the Well Depth is decided based on the square of the position of the cell and the remainder of when it is divided by a prime number. (We know it sounds really complex… but this is how the ratios of the wells are calculated to maintain a balance of magnitude across the face of the device.)
The equation looks like this:
Well Depth = (n² modulo p)
(Note: there will not be a quiz!)
As it was stated, both of the devices use the identical calculation when coming up with their wells… but there is one important change – the well bottoms are flat on the standard QRD and angled on the angled quadratic. This change makes this diffuser perform differently in 2 key ways:
- The Diffusion Pattern is wider on the angled QRD.
- There is a more subtle transition from one frequency to the next on the angled QRD.
When you look at the two sets of polar pattern above, you will notice that the Angled QRD has a wider pattern, as shown in the first-column, horizonal polar pattern (at 2000Hz especially), where the standard QRD is a more forward-focused pattern.
What does that mean in practice?
Both of these diffusers have a 1D pattern, but the flat bottoms of the standard QRD primarily use diffraction and incidence angle to widen the diffusion… the rest of the diffusion works on the principal of phase offset from the depth of the wells and the time of travel. The Angled QRD introduces an angle which means that one side of the well is deeper than another. This changes the reflection angle, time of travel, and, in turn, degrees of phase shift depending on where the sound strikes the inside of the well. This modification smooths the transition of phase from well to well – as the wells themselves have a range of phase change. This angle also causes the sound to be redirected toward the inner walls of the wells, causing it to change direction from the angle of incidence – widening the pattern further, changing the travel time, and basically bouncing sound around more.
There are some situations where the standard QRD‘s narrow pattern and well-defined transition frequencies may be preferable. In some practice rooms or larger listening spaces, there may be a need for the diffusion to be a little more directional, maybe to hit (or avoid) a certain position in the room. In these scenarios, the standard quadratic may be the recommended choice. In other spaces where you want the reflections to spread out more rapidly – maybe in smaller rooms or spaces where you need to get more coverage from ceiling reflections – then the angled quadratic may be more appropriate.
In closing, while these two devices have a nearly identical design, a small difference can have a big effect on the performance of the diffuser – and how you use them.
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.
Throwback Thursday: Diffusion Vs. Absorption
Posted by Acoustics First in Absorption, Diffusion, Product Applications on May 22, 2025
On this Throwback Thursday, we look back at a popular Sound and Communications article about why sound diffusion is so much more complex a phenomenon than sound absorption. In this article, we discuss some of the different variables associated with the quantification of diffusion – magnitude, phase, frequency, direction, etc. When comparing its properties against absorption, which is simply the reduction of energy at specific frequencies, the argument is cemented as to why a single-parameter coefficient is insufficient to fully express the phenomenon of acoustic diffusion.
Read the article here:
PDF Version of Sound and Communications Article.
Revisit the original post here:
https://acousticsfirst.info/2020/03/24/acoustics-first-talks-diffusion-in-sound-communications/
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