Posts Tagged acoustics first

You say “Diffuser,” I say “Diffusor”

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.

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Eight very different 2′ x 2′ sound diffusers.

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.

The Pyramidal Diffuser is a classic geometric shape that provides 4 surfaces to break up the acoustic energy, these facets are also asymmetric, which prevents lobing, and reflects energy in different directions.
The QuadraPyramid™ offers the same benefits as the pyramidal, but in a lower profile, and 4 times the number of faces in the same footprint. These offer more control over high frequencies, that respond well to the multitude of smaller faces, due to their shorter wavelengths. These work well in spaces with lower ceilings to help control flutter echoes.
The Double-Duty Diffuser™ is a polycylindrical barrel diffuser, which redirects the energy in a hemispheric pattern. This pattern is easy to predict when trying to help distribute energy to many people – either in an audience, or players in an orchestra. This has the added benefit of a large cavity which works well as a bass trap.

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.

The Quadratic Diffuser is a 1D Quadratic Residue Diffuser that diffuses across the wells. This pattern looks similar to that of a Double-Duty diffuser, but is more disruptive to the phase relations of the reflections and is tuned to a narrower frequency band. These diffusers are often installed with the wells up in the ceiling or wall, which means they do not protrude from the surface, providing a clean flat look.
The ArtDiffusor® Model C is a high-performance 2D Quadratic Diffuser. It uses blocks instead of wells, and has angled caps to further assist the development of the hemispheric diffusion pattern. The Model C is a hybrid Quadratic and Binary design. It is quadratic in the heights and binary in the distribution. This unique combination of mathematic functions and the inclusion of angled reflections adds a new dimension when installing arrays of diffusers to reduce lobing and improve performance.
The ArtDiffusor® Model F is an interesting spinoff of the Model C. The Model F is a specialized low-profile version of the Model C, which uses smaller block structures to tune it to higher frequencies. Like the QuadraPyramid above, the larger number of smaller surfaces tunes this device to frequencies with a shorter wavelengths, in a low-profile design. The Model F is ideal for controlling flutter, ringing and high frequency comb filtering artifacts in spaces with limited space, or specific constraints.

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.

The Aeolian™ Diffuser is, at its core, a classic quadratic diffuser. The main difference is that, instead of limiting itself to the standard blocks and wells of a single size, the surface has been modified using bicubic interpolation. So instead of every frequency interacting with 2″x2″ blocks, they hit a rolling organic surface, which will redirect different frequencies in different ways. The different wavelengths interact and reflect off the surface differently – short wavelengths are more specular and longer wavelengths find a larger section of surface to redirect them.
The ArtDiffusor® Model D is another organic diffuser design, but it uses several different modifications to the standard quadratic design. Most quadratic diffusers start with square or rectangular blocks and wells. The Model D started life as rings of different sizes and spacing based on Maximum Length Sequences that were different thicknesses. Those rings were then raised to different heights based on the Quadratic Residue calculations. Randomness was introduced with Boolean logic, which would add height to some rings while subtracting from others when they crossed each others path. The whole geometry finally went through the bicubic interpolation to smooth the transitions. This completely original design is optimized for mid-to-high frequency diffusion and maintains a highly asymmetric diffusion pattern from any angle, at any frequency within the design range.

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.

Big 3 Studio has Aeolians on the rear wall and black Model C’s and Model F’s on the ceiling above the console.

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.

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Project: Beginning to End – Biltmore Park Clubhouse

Occasionally, we get the opportunity to show the entire process that goes into a project, and today we have one which we will run through – beginning to end.

Biltmore Park clubhouse was getting a full aesthetic and acoustic makeover. Acoustics First® was asked to collaborate with Harmony Interiors on the acoustic panel recommendations for this project. After an initial consultation, a layout was developed that would attain the desired effect.

Along with this layout, a pre and post treatment acoustic performance was predicted and supplied.

Biltmore Park Clubhouse Acoustic Calculator
The prescribed treatment should take the reverb time from 2-3 seconds down to around 1 second.

After the treatment was approved and ordered, the panels were manufactured and supplied to the customer for install. This installation included several Sonora® panels for the ceiling, and others for the walls. After the customer received the order, Harmony Interiors began the installation.

Installing z-bars to the Sonora® panels
Z-bars are mounted to the Sonora® panels to facilitate hanging.

Installing the wall bars using a template.
Using a cardboard template to help mark the wall bar locations, the mating Z-bars are installed to allow the Sonora® panels to be mounted easily.

Sonora panel is hun on the z-bars
The Sonora® panels are hung by mating the z-bars on the panel with those on the wall.

Installed ceiling section of Sonora® panels
Ceiling sections are installed using the initial layout as a guide.

completed ceiling install
Final configuration of the panels when completed. (Upper room and ceiling.)

Sonora® panels installed on the lower walls.
Sonora® panels installed on the lower walls of the clubhouse.

BONUS! This is often all the information we receive… along with some comments about how great the room sounds. But on this occasion, we were able to obtain a full before and after comparison of the effects of the treatment!

Video of the room – pre and post treatment!

The Harmony Interiors installation crew had the foresight to shoot a bit of video highlighting the sound of the room just before and immediately following the installation of the Sonora® panels. This is certainly an ear opener!

The second benefit of getting this before-and-after comparison video is that we were able to critique our initial predictions of the pre- and post-treatment reverb times.

actual reading of before and after RT times
The analysis shows a pre-treatment RT-60 of about 2.4 seconds and a post-treatment RT-60 time of roughly 1.2 seconds. This is right in line with the performance predictions that were calculated in the very beginning of the consultation!

We hope you enjoyed seeing this acoustic project from the initial consultation and layout phase, through the installation, and to completion.

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Absorption & Diffusion – The Construction Specifier

For the May 2022 edition of “The Construction Specifier,” Acoustics First was asked to illustrate the use of absorption and diffusion in creating optimal acoustic spaces. The article is a great reference for understanding the types of acoustic absorbers and diffusers, as well as some use scenarios like offices, critical listening spaces, and larger communal spaces.

Note: This version has been edited and the advertisements are removed. The full published version of the May 2022 digital edition can be found on The Construction Specifier’s website here.

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Sonora® Panels help Citizen Heights Church

Citizen Heights Church found a great facility to move into, even during a global pandemic. However, a major obstacle was that the facility had a traditional cathedral ceiling and a nearly 6 second reverb time was not compatible with their high-energy modern services. To address this issue, they included custom Sonora® panels in their overhaul. This decision helped take their 6 second reverb time down to an incredible 1.5 seconds – creating a space that maintains a level of intelligibility which would have been impossible otherwise.

Read the full story here.

Original Technologies for Worship article link.

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