The Aleph1 cabinet features a multi-material layered structure which is derived from the conclusions of the 3D printed material blanks acoustic measurements.
Rigid Exterior Shell
The exterior layer is made of a rigid material and provides the structural integrity of the cabinet.
Trapped within the wall-thickness of the cabinet is a flexible core that helps neutralize the cabinet response.
Rigid Segmented Interior
The interior of the cabinet is another rigid, acoustically reflective layer, comprising of 680 diamond-like segments.
The cabinet exterior shell acts as an exoskeleton holding everything together. The shape, besides the intentional design cues, is functional in terms of acoustic performance. The non-parallel surfaces with continuously variable radii and complex curvatures serve three purposes:
- Helps with cabinet diffraction allowing the wavefront to propagate cleanly in the room.
- Acts as an acoustic diffuser in the room by nonuniformly dispersing any sound wave that hits it.
- Combats cabinet resonance by responding differently to different frequencies at any point measured.
The measures to avoid cabinet resonance don't stop there. The wall thickness of the cabinet is variable throughout, both in overall thickness and also in the material distribution (continuously variable ratio of flexible and rigid materials).
Also, the internal layer is made of the same rigid and acoustically reflective material as the exterior shell. However, it is not a continuous 1-piece structure. Instead, it's made of 680 diamond shaped segments of variable dimensions and curvatures.
This, along with the earlier mentioned features means that theoretically there's no one single frequency that excites the entire structure, and the resonant frequencies of each individual element would interfere with the rest resulting in a more neutral sounding cabinet.
The Aleph1 bookshelf speaker prototype was printed by Stratasys on a multi-material Connex series 3D printer using a combination of rigid and flexible materials, and water soluble support.
The driver used in the prototype speaker is a 4" Morel coaxial unit with integrated crossover.
The terminals are fully insulated, gold-plated, pure copper 5-way binding posts connected to the driver using pure copper Morel speaker wire.
The speaker stands on 4 machined and chrome plated stainless steel spikes (not shown).
The text on the back of the speaker reads:
"Designed by Boaz Dekel for the Bezalel Academy of Arts and Design in cooperation with Stratasys and Morel"
The Aleph1 3D printed speaker cabinets leverage additive manufacturing technologies to address age old-issues in loudspeaker design. The ability to produce complex geometries of multiple materials, each with different physical and mechanical properties, opens the door to new approaches and acoustic solutions.
When a speaker reproduces sound, it outputs audio signals both towards the front (towards the listener) and towards the rear (within the speaker cabinet). The rear firing signal is called the back wave.
Back wave distortion occurs when the rear firing signal reflects back from the cabinet walls and interferes with the signal coming out the front.
Most speaker manufacturers address this issue with acoustic absorption; acoustic foam or other porous or fibrous materials are introduced into the cabinet in order to transform the acoustic energy of the back wave into heat.
By doing so, the effect of back wave distortion is reduced to acceptable levels. However, using too much absorption results in muffled, or"dead" sounding speakers.
Little absorption meant a more natural and open sound, all the while being susceptible to back wave distortion, and heavy absorption meant little to no distortion at the cost of a less lively, more muffled sound.
Aleph1 speaker cabinets address the issue of back wave distortion without using acoustic absorption. Instead, they leverage innovative geometry manufacturable only by 3D printing, to direct the back wave into a perpetual self-feeding loop that prevents it from interfering with the signal outputting to the front.
In doing so, the acoustic energy of the back wave is preserved and serves to project sound through the speaker cabinet. Allowing the back wave to participate in the process of sound reproduction resulting in a clean, open and natural sound with high detail and great separation.
3D Polymesh FDTD Impulse Response Simulation
The hypothesis of the perpetual self-feeding loop creating an infinite path within the speaker cabinet was put to the test using FDTD (finite difference time domain) wave propagation simulation software on 3D polymesh models representing the cabinet air volume.
Fortunately, the results were surprisingly optimistic and allowed for a degree of optimization to further improve performance.
The FDTD results showed significant attenuation of back wave reflections. Just 0.13 of the original pulse was recorded reflecting back to the point of origin.
Taking under consideration that it's a purely geometric simulation that does not account for the natural absorption coefficient of the cabinet, meaning the boundaries reflect 100% of the signal, the assumption is that a live measurement will show back wave reflection attenuation greater than a factor of 10 without any use of internal acoustic absorption within the cabinet.
Cabinet resonance is a serious challenge in loudspeaker design.
For speakers to be able to reproduce music faithfully and accurately, they must not overly accentuate or attenuate any particular frequency or band of frequencies.
However, every material and every geometry has a resonant frequency: A certain frequency that will create sort of a feedback loop within the object and amplify itself indefinitely, or to the point of mechanical failure (whichever comes first).
This, in turn, means that every driver, cabinet, and room have resonant frequencies as well. In rooms, these resonances are known as standing waves and room modes.
Luckily, music rarely ever involves pushing pure sine tones for any significant duration, meaning there's no danger of physically damaging audio equipment by simply playing some tunes. However, the music content being played does include said resonant frequencies among others and they will naturally be accentuated by the unit outputting them.
When the effect is subtle it's referred to as "character" or "color", but when the effect is severe it's outright distortion, like applying an constant EQ (equalizer) on everything the speaker unit plays.
The most common ways to combat cabinet resonances and allow the speaker to play accurately, is to avoid parallel surfaces within the cabinet, and to construct the cabinet from a combination of different materials (with different resonant frequencies respectively), so that the interference between them will likely break any chance of uncontrollable resonances.
The Aleph1 cabinet geometry is off to a good start right off the bat with its streamlined, non-parallel and continuously variable design. But it doesn't stop there.
Acoustic measurements were conducted in order to learn how different materials and configurations affect a given geometry's acoustic response. The conclusions were then implemented in the cabinet structure.
3D Printed Materials Impulse Response Spectral Analysis
Inspired by the material testing process as described on Wilson Audio's website, a similar experiment was conducted on 3D printed material blanks.
A steel bearing ball was dropped from a controlled height onto different 3D printed blanks, and the resulting audible impulse was recorded and analyzed.
The blanks were all consistent geometrically and dimentionally, and although the experiment wasn't conducted under ideal conditions, the results were still valid comparatively.
Among the parameters tested were: Comparisons between different homogeneous materials, homogeneous materials against multi-material configurations, effects of different material ratios within a multi-material configuration, effects of a different layer count within a multi-material configuration, effects of different distribution of materials within multi-material configurations, and more...
The measurements led to some interesting and counter-intuitive conclusions.
Material Blank Acoustic Measurement Results
The Aleph1 speaker concept utilizes modern manufacturing techniques to address age old challenges in loudspeaker design.
Originally a design exercise, the Aleph1 concept explores the potential added benefit of additive manufacturing (3D printing) to the loudspeaker industry.
The new geometries and material configurations made possible by additive manufacturing inspired a new look at how speakers are manufactured and how they produce sound.
By breaking free of the constraints of traditional manufacturing technologies and completely disregarding commercial viability, Aleph1 speakers are the results of a puristic effort seeking to confront the problems of back-wave distortion and cabinet resonance in ways that until now, have not been possible.
Simply put - there are many excellent sounding speakers in the world, the Aleph1 speakers just do it differently.
The Aleph1 speaker concept was conceived by Boaz Dekel for his thesis project in Industrial Design at the Bezalel Academy of Arts and Design, in cooperation with Stratasys and Morel.
Form Follows Function
The primary challenge in the design of the Aleph1 speakers was finding a way to communicate externally the internal structures and geometry. The design balances fine detail intricacy with the understated nature of the cabinets' hidden internal features.
Other than the exterior contours following the distinctive shape of the interior volume, it was also necessary to portray the layered and segmented structures that define the Aleph1 cabinets' performance characteristics.
The design detail in the inner-toroid of the bookshelf cabinet hints at and represents all of the structural elements of the cabinet: It shows the layered structure with the exterior layer intersecting and looping into itself, as well as the inner-most layer segmented into continuously variable diamond-like sections. It also helps define the directionality of the geometry, all the while remaining subtle and unobtrusive to the general streamline feel and aesthetic.
The sculpted metal stand of the Aleph1 bookshelf speakers complements the cabinets without competing or drawing too much of the attention from them.
In the case of the subwoofer it was decided to visually differentiate it from the bookshelf speakers and avoid it being just an issue of scale. It is commonplace in 2.1 audio setups that the subwoofer varies in appearance from the left and right channel speakers, with many examples of mixed brand setups; where a subwoofer from brand A is matched with stereo speakers of brand B.
This was an opportunity to explore the design possibilities of the Aleph1 spiraling toroid concept, and create a new iteration for the concept that is radically different and yet unmistakably related to the bookshelf speakers.
Thoughts on design, 3D printing, and consumer products...
3D printing is still considered an "exotic" manufacturing technology. For numerous good reasons, it isn't yet fully accepted as a method of creating end-use consumer products.
As an academic work, the Aleph1 project looks ahead to a time where 3D printing mainstream and consumers can customize digital models to their specific needs before having them manufactured.
Today, 3D printed products generally have a very indicative, almost stereotypical aesthetic. They are usually complex, fractal, cellular or skeletal geometries, utilizing micro-structures to cut down on weight, material costs, and machine time. These new geometries are consistent with the fortes of 3D printing - the ability to realize "impossible" complexities at no additional cost while also catering to all functional, mechanical and structural requirements.
But what if 3D printed products weren't so "in your face" about it? What if it wasn't so obvious and easy to tell whether a product was 3D printed or not? What if it didn't matter?
The vast majority of consumers don't care much if a product was CNC-milled or CNC-lathed. They don't care if a part was injection-molded or rotation-molded. It simply isn't a selling point. What if 3D printing was like that, and 3D printed products were judged by their merits, not by the technological hype?
This project explores the potential aesthetics of this new era of consumer products by subtle geometric decisions that challenge traditional manufacturing methods.
From the outside, it isn't obvious the Aleph1 cabinets are 3D printed. They may just as well have been injection molded. Only if one looks inside they'll notice the complex, segmented, self-intersecting geometries. And only if one studies the cabinets closely they'll notice the subtle details and "gotcha's" of 3D printing externally:
The exterior diamond pattern on the bookshelf speakers, for example, utilizes a slight negative draft angle - similar to a dove-tail. This subtle design detail makes the shadows between the diamonds sharper and darker, making the pattern more defined even though it is just 1mm deep. The negative draft angles also mean undercuts - making the geometry impossible to extract from rigid molds and therefore impossible to mass-produce using traditional industrial manufacturing methods.
This is the type of attention to detail the Aleph1 project hints we'll see more of in the future of 3D printing. At least this is what I, as a designer, would like to see more of as the technology begins to make its way into our everyday lives.
Inventor, Designer and Project Manager - Boaz Dekel
Thesis Project for the Bezalel Academy of Arts and Design
Prototype 3D Printed by Stratasys
Audio Components by Morel
Intellectual Property Management by SNE Rosetta IP
Design Supervisor - Dori Regev
Science Consultant - Ronny Barnea
FDTD Software - Jonathan Sheaffer
The "correct" size of a speaker is relative to the size of the room it's in. A 4" driver is indeed rather small and we shouldn't expect it to be something it is not. It simply cannot move as much air as a larger speaker can. It does however get fairly loud, and can prove to be more than enough for small spaces.
Just because a speaker is small doesn't mean it can't be good, and people in tight spaces shouldn't have to compromise on sound quality.
Having said that, there's virtually no reason to limit the Aleph1 concept to 4" drivers. The cabinet can theoretically be made larger to accommodate a larger driver. It's just a matter of cost.
The principal of the infinite cabinet eliminating back-wave distortion applies to all frequencies. It seemed redundant to have multiple spirals to treat separate drivers when the entire signal could be handled as a whole by using a coaxial driver. It just makes more sense to have one structure interact with the entire back-wave as a single source.
There are many excellent sounding speakers in the world. The Aleph1 speakers simply do what they do differently from all the rest. The physics behind how they work is different, and therefore they will inherently sound different.
Whether you will or will not be able to hear the difference will depend on you and your circumstance; primarily the source material and signal chain, your listening environment, and ultimately how well trained a listener you are.
So in short, do they sound different? Yes. Because physics. Will they sound different to you? I hope so. Will they sound better? Only you can answer that. To me they sound fantastic.
I get this type of question a lot, usually followed by the claim that wood is the "best" material for speaker cabinets. This notion, in my opinion, is unsubstantiated and narrow minded. There's nothing inherent about wood that makes it the ultimate material for speaker cabinets. Speakers certainly aren't the reason for the existence of trees, therefore it's highly unlikely (and quite arrogant to assume) no other material in the universe could perform as well, if not better, in our human applications regarding sound reproduction.
Speaker cabinets are traditionally made out of wood because it's readily available, affordable, easy to work, and as it turns out - sounds pretty good, too. But to make the jump and claim it's the "best" is simply lazy and uninspired.
What is "wood" anyway? Very few cabinets are constructed of natural wood stock nowadays. It's much more likely for cabinets to be made of chip-board (which is hideous), plywood (which is wood veneers glued together), or MDF (which is sawdust compressed with resin). This isn't to say wooden cabinets don't sound good, I'm just making the point that even within the "wood cabinet" category, there's more to it than just trees.
Besides that, speaker cabinets have been built from virtually every material by now. Concrete, glass, granite, aluminum, acrylic, gold, fiberglass, carbon fiber, and yes - also resins and polymers (aka "plastics") and the list goes on. Some of the best-known speakers in the world are made of these "alternative" materials.
At the end of the day, different materials have different physical properties. There's no reason an engineered material with the desired properties should fall behind a "natural" material in terms of acoustic performance.
The best thing to do would be to check all of our preconceived notions at the door and let our ears be the judge.
Polyjet 3D printers work very similarly to inkjet document printers. Instead of placing tiny drops of ink on a page, the print head places dots of photo-curable polymers on the print bed. After each pass the bed descends a few microns allowing a new layer to be printed on top the previous one, building the object form the bottom up.
Just like an inkjet printer can print using multiple colors from different cartridges, Polyjet 3D printers can print with multiple materials from different cartridges. This multi-material capability paired with extremely high detail resolution and good surface finish, are the primary benefits of using this technology.
Polyjet materials are generally not considered "end-use" materials and are sensitive to deformation if exposed to high temperatures. In the case of the Aleph1 cabinets, we're talking about a very substantial object. The walls of the cabinet are so much thicker compared to typical plastic parts, that they do a much better job at handling heat and there's no danger of the cabinet deforming under reasonable conditions. Having said that, new materials are constantly being developed with the aim of reaching "end-use" standards, and they will be evaluated and considered once they become available.
It's true that FDM printers that extrude filament to produce the object can print with end-use thermoplastics such as ABS. However, as of today, they suffer in terms of print size, detail resolution, and accuracy.
Other 3D printing methods involve a high powered laser that traces each layer to form the object. The smaller the beam is, the higher the detail it can produce. It may seem like a benefit but it's a double-edged sword. A small beam also makes it much more difficult to trace large surface areas. Polyjet technology is very efficient in covering large areas and therefore is the best choice for producing objects that feature extreme wall thicknesses, such as heavy speaker cabinets.
It's true the world renowned Bowers and Wilkins Nautilus speaker, introduced in 1993, employs a spiral design to address cabinet diffraction. However, it only does so for the low-frequency driver. Also, the Nautilus spiral is finite and terminates at the center, from which theoretically, the rear-radiation would begin to make its way back.
The Vivid Giya speakers feature spiral structures as well. It is unclear from my research whether the spiral is there for acoustic or aesthetic purposes (or both), nevertheless the spiral is either finite or "spills" back into the main volume of the cabinet in a way that doesn't address back-wave reflections with the same approach as the Aleph1 concept.
The Aleph1 cabinet is the only one that features a self-feeding closed loop that creates a perpetually infinite path in which the back-wave can propagate without ever returning.
Thank you for your interest in the Aleph1 speaker concept
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