3D printing Audio DIY Loudspeaker Speakers Technology

A versatile 3D printed coaxial loudspeaker – RD Physics CX2

The first version of our 3D printed coaxial CX loudspeaker series was made using the Desktop Metal Forust method, which is, at the moment, too expensive for most DIY audio enthusiasts. Therefore, the CX2 was designed based on fused filament fabrication (FFF).

3D printing gives design freedom

The starting point for the design is simple but effective: sealed enclosure and coaxial driver. This inherently gives us controlled cone displacement in the low-frequency region and a coherent radiation source in the crossover region. 3D printing allows to easily implement two more acoustically beneficial geometries: large roundovers and compound curved walls. These translate into a Minimal Edge Diffraction Enclosure (MEDE™) and reduced panel vibrations, respectively. Curved walls mean that the loudspeaker requires a stand. This requirement can be turned into a benefit: the symmetric loudspeaker can be tilted or laid on its side when placed on a so-called Isopodd stand 3D printed from soft TPU material. 3D printing allows complex shapes at no extra manufacturing cost. For example, the front baffle is stiffened on the inside with a honeycomb strucure that acts also as support for the overhangs, but robs very little internal volume.

What you need to build your own CX2

  • 3D files for 3D printing, sold on Etsy. Dimensions 210x273x170 mm, ~1200 grams of filament.
  • SB Acoustics SB13PFCR25-4 COAX or SEAS MP15 (contact us)
  • Active crossover, miniDSP recommended
  • Two channels of amplification per speaker, ICEpower module recommended
  • Neutrik NL4MPR SpeakON connectors and fastON crimp connectors
  • 4.2 mm wood screws
  • Bitumen or similar visco-elastic damping sheet and fibrous damping material such as pillow stuffing
  • Soldering capability (super easy)

How to build it

3D print the enclosures using the files mentioned above. It’s a single-piece print with no support needed. Wood-filled PLA or similar material is easy to sand and no other surface finish besides sanding is needed. If you are using the SEAS drivers you also need to print the TPU gasket/adapter. The speaker can be tilted and rotated when you print a small stand for it from TPU material. Some rubber feet on a plate will do the same job just fine. The assembly order is as follows:

  1. Finish the outside of the enclosure and make sure the driver and SpeakON connector fit.
  2. Line the inside with bitumen damping material and fill it quite densily with wadding.
  3. Solder wires to the speaker drivers and crimp fastON connectors at the other end. Mark woofer and tweeter positive and negative wires.
  4. Feed the wires through the SpeakON connector opening and mount the driver using wood screws. Use gasket/adaptor if you have the SEAS driver.
  5. Connect the fastON connectors to you SpeakON connector and mount it.
  6. Setup your bi-amping and crossover configuration. A good starting point for crossover frequency is 2 kHz. On-axis response will be bright, so keep that in mind when equalizing. Some toe-in may be beneficial.


Bluetooth speaker 3D printing Audio Circular economy DIY Loudspeaker Recycling Speakers Sustainability

Bluetooth loudspeaker without an internal battery

What’s wrong with having batteries in your portable boombox?

Wireless electronics, such as bluetooth speakers, are extremely popular nowadays. All such devices must have a power source and typically it is a lithium-ion battery. However, the demand for battery raw materials is rising at an alarming rate:

The supply of some of these [battery] materials, in particular cobalt, natural graphite and lithium, is of concern today and for the future in view of the large quantities needed and/or very concentrated supply sources.

European Battery Alliance (EU)

As we have discussed earlier, when launching our Circular Sound program, the best solution for reducing reliance on critical raw materials is to reduce their use. The RD Physics BB1 boombox enables you to do just that. It is designed to use existing external power sources and therefore no new batteries are needed. Battery service-life or battery replacement is no longer a concern.

Alternatives to dedicated batteries

The BB-project started by looking at how power tools are sold without accompanying batteries. The idea being that the user needs only one battery (plus spares) that fits all tools. While this approach reduces the amount of batteries needed, it is also used to tie the customer to a specific brand. We wanted a universal solution and therefore the USB-C standard was chosen. The BB1 and BB2 boomboxes use a USB-C port as an interface to feed power to the amplifier. The boombox can be connected to any USB port: power banks, phone chargers, laptops, extension cords, solar panels etc. Obviously, the input voltage and current draw is limited, which leads to limited sound pressure level (SPL).

The weather-proof USB-C port is located at the top.
Frequency responce of 3D printed bluetooth speaker.
Frequency response of BB1 at maximum drive level.
BB2 boombox with Dayton Audio RS100 drivers.
Frequency response of BB2 at arbitrary drive level.


What you will need to build your own batteryless boombox:

  • Geometry files for 3D printing (free under Creative Commons License at Thingiverse)
  • 3D printer big enough to fit a 235 mm diameter sphere
  • Slightly over 1 kg of filament depending on your settings
  • Two active drivers. Either Peerless 3″ (BB1) or Dayton Audio 4″ (BB2)
  • One 6½” Dayton Audio passive resonator
  • A Sure (Wondom) bluetooth board with additional cables set
  • USB-C panel mount plug (from eBay) and 6 mm DC plug
  • Wood screws (4.2 mm for the drivers and resonator, 3 mm for the BT board)
  • Drawer handle, IKEA Eneryda 703.475.16
  • Damping material (bitumen or similar automotive damping mat and fibrous wadding, for example pillow stuffing)
  • Optional: Wall mount bracket, Genelec 4000-410B
  • Minimal soldering capabilites

The enclosure for the BB1 and BB2 can be downloaded from the link above. Assembling everything takes 30 minutes.

3D printed boombox enclosure
3D printed enclosure ready for assembly.

How to build the BB1/BB2 bluetooth speaker

  1. Start by soldering the 6 mm DC plug to the USB connector. Red (+) goes to center pin and black (-) to outer shell.
  2. Connect DC power and speaker cables to bluetooth board and fasten the board inside the enclosure by tightening the screws via the driver openings.
  3. Mount the USB connector and handle.
  4. Line the inside of the enclosure with bitumen or similar visco-elastic damping material. Heat will aid in conforming to internal shapes. Make sure the damping material is fully bonded to the walls.
  5. Bring the speaker wires through the driver openings and solder them to the drivers. Make sure polarity is the same for both drivers. Then fasten the drivers using wood screws.
  6. Fill the enclosure with fibers (cotton, polyester, wool etc.) and fasten the passive resonator.
  7. Optional: Attach the wall mount bracket.
  8. Connect a USB port and the bluetooth board powers on automatically. Pair your signal source with the device (“WONDOM”). Enjoy!
BB1 portable bluetooth speaker with 3D printed enclosure.
BB1 ready to rock.

Assembly instructions

Concept and sound test

Circular economy 3D printing Audio Loudspeaker Recycling Speakers Sustainability

Circular Sound – Disrupting the industry with 100% recycled loudspeakers


The loudspeaker industry, like all other industries, needs to transform into a circular economy model. Why? because only 8.6% of the materials we use circulate back into the economy, according to the Circularity Gap Report 2021. We need to increase this number in order to reach the Sustainability Development Goal 12.5 set by the United Nations:

By 2030, substantially reduce waste generation through prevention, reduction, recycling, and reuse.

United Nations Sustainability Development Goal SDG 12.5

Circular Economy of Loudspeakers

Some loudspeaker manufacturers use recycled or renewable enclosure materials, but the biggest problem is circulating the electronics and loudspeaker drivers back into the economy. There is an abundance of old loudspeakers being discarded or sold very cheap every year, because demand for old models has diminished. Buying new loudspeakers made from virgin materials is not sustainable, especially due to the rare-earth elements (REE) used in loudspeaker magnets.

Rare earth elements (REEs) are essential for manufacturing permanent magnets. Permanent magnets are critical components in most decarbonisation technologies.

European Union EIT Raw Materials

The European Union is dependent on imported magnets and REEs. A circular economy model would not only be good for the environment, but also for the reliability of supply chains.

Additive manufacturing enables circular economy

Additive manufacturing offers many opportunities for a circular economy, where repair and remanufacturing are some of the best options to reduce the consumption of mass-produced products made in far-away lands. Circular economy can be described by the 6 REs:

  1. REduce – Don’t buy anything
  2. REuse – Buy second-hand
  3. REpair – Fix it, if it’s broken
  4. REmanufacture – Make something new using old components
  5. REcycle – Cycle the raw material back into the economy
  6. REcover – Burn for energy

As far as loudspeakers are concerned, the best option is of course not to buy anything. The second and third best options are to buy used loudspeakers or fix broken loudspeakers. These two options, however, do not consider the fact that the user may want something different compared to their current product or what is available second-hand. In other words, it does not help if a product can be used forever if nobody wants it anymore. Circular Sound tackles this issue by relying on remanufacturing with the help of 3D printing. In this context, remanufacturing means using the drivers and electronics from old loudspeakers and 3D printing a new enclosure. Obviously, the material of the new enclosure needs to be sustainable, too. Recycled and bio-based plastics are promising, but require special design considerations to obtain the necessary acoustic properties from the enclosure.

3D printing a bio-based loudspeaker enclosure

RD Physics CS-012 proof-of-concept prototype

The RD Physics CS-012 is the first loudspeaker design in the Circular Sound line-up. The donor components come from an old Yamaha YST-SW012 bass-reflex subwoofer. Additive manufacturing was used to produce a smaller, sealed enclosure loudspeaker. The material used in the prototype is a bio-based material produced by BrightPlus. It has a natural dye made from woad by Natural Indigo Finland. The original Yamaha loudspeaker is designed to be used as a single subwoofer unit placed somewhere on the floor out of sight. The new product, on the other hand, is designed to be used in stereo configuration (2 pcs) and placed under the main speakers. It serves a different function compared to the original product, but no new materials need to be consumed. We are not injecting a new product made from virgin materials into the economy. Instead, we are taking two old ones out and replacing them with one value-added product. This is what Circular Sound is about. You don’t have to wait for distributors to bring sustainable products to your local market. You can start making these today. The files are shared for free under a Creative Commons license on Thingiverse.

Near-field and far-field magnitude response.
Audio 3D printing Circular economy DIY Loudspeaker Speakers Technology

3D printed wood – A revolutionary way of making loudspeakers

3D printed loudspeakers do not have to be made out of plastic anymore. There is a new way of 3D printing wood called Forust. It is a binder jetting process where upcycled sawdust is used together with a binder to form the closest thing we have to 3D printed wood. We are particularly interested in the possibilities this offers loudspeaker manufacturers.

RD Physics CX1 – A coaxial loudspeaker

RD Physics has been developing speakers with full-range drivers for some time now and while they have their inherent benefits, it is time to look what coaxial drivers have to offer. The starting point was a spherical shape, which is known for its benefits. However, the limitations in build volume favored a shape closer to a rectangular cuboid. The shape of the CX1 has the largest possible roundovers, with the constraints imposed by driver size and maximum baffle dimensions. This is to reduce edge diffraction. The sides are compound curved to maximize stiffness. There is also internal ribbing to stiffen the enclosure without taking up internal volume like a sandwich structure would. The enclosure is made in two parts; the front baffle has a separate cover that conceals the driver flange and mounting screws. The driver is a proprietary SEAS unit designated MP15 (15 cm diameter). The idea is to have an external active crossover and bi-amp the loudspeaker via the Neutrik SpeakOn 4-pin connectors at the back.

3D printing a loudspeaker using Desktop Metal Forust method

The geometry files were sent to Forust for 3D printing. The chosen colour is “natural” with the artificial wood grain introduced during manufacturing. The result is a structure that looks like plywood. Parts can be ordered without the grain and with darker colours, too. The grain is more interesting, however, because various surface texture effects can be achieved by aligning the layers at low angles relative to the principal axes of the printed shape giving a zebra stripe effect.

Post-processing of 3D printed wood

The parts printed with the Forust method can be sanded smooth, but it is not like sanding natural wood. The surface can be varnished, but not stained. The Forust material does not absorb wood stain. It does not tolerate ethanol and perhaps other solvents either. Long-term exposure to water should be avoided, otherwise there will be is a sticky brown residue on the surface. Although a wooden look can be mimicked, post-processing is not similar to wood. Instead, it resembles the wood-filled polymers used in our previous builds. This is not a serious drawback, it just means that 3D printing skills are more useful than woodworking skills. In terms of aesthetics this is the closest thing available for increasing the acceptance of 3D printed loudspeakers in the audio community, where wood veneer is the go-to solution.


Technology 3D printing Audio DIY Loudspeaker Speakers

Practical 3D printed desktop speakers – FR4

The third version of our 3D printed full-range FR loudspeaker series used metal-filled filament to add density and stiffness to the enclosure. It worked in that regard, but the material was unpractial due to brittleness both during printing and in the final product.

What has changed compared to the FR3 speaker

For the fourth version we switched to wood-filled filament, which is more ductile and easier to process. The surface is quite nice straight out of the printer thanks to the matte surface. A quick touch with an orbital sander gives a smooth finish. The spherical shape of the enclosure remains the same as in the FR3 speaker, because it was proven to be very good in terms of resonances and edge diffraction. The diameter of the driver, enclosure and tripod legs was reduced to obtain a more slender design for desktop use. The binding posts are upgraded to sturdy Dayton Audio binding posts. The driver used is the Tang Band W3-1878, and the leadscrews for the legs are 12 mm. Leadscrew nuts are bonded into recesses in the enclosure and allow for adjustment of the legs. Small TPU feet can be printed and placed at the ends of the leadscrews in order to avoid scratching the desktop. These are satellite speakers and need a subwoofer to compliment the lower frequency spectrum.

You can 3D print your own sub and satellite system by purchasing the STL files from our Etsy Shop.


Technology 3D printing Audio DIY Loudspeaker Speakers

Powerful 3D printed 5 inch subwoofer – SW2

Subwoofer Concept

Our previous 3d printed subwoofer, the SW1, is a 13 liter subwoofer with a 6.5″ driver, a matching passive radiator and a plate amp. We wanted to develop something smaller that would still offer the bass extension that satellite speakers so badly need. The result is the SW2 using a Tang Band W5-1138 5″ long-throw driver and the same Dayton Audio DSA175 passive radiator as in the SW1. The enclosure is now only 5 liters and much easier to fit on a desktop. The passive resonator allows tuning the resonance frequency to avoid overlap with room modes, for example. The spherical shape is optimal for material use and stiffness. Combined with the small diameter driver with large surrounds, the appearance is quite unique. If a traditional box is what you want, then this build is not for you.


The measured resonance frequency of the passive radiator indicates that some air-coupling occurs due to the downward firing placement. Simulated resonance frequency matches the measured value (53 Hz) when 16 grams of added mass is used. Mass can be further added using washers to tune the response. In practice, the frequency response starts to drop below 50 Hz. The Arylic amplifier offers DSP capabilites and using a computer as the source allows unlimited DSP with zero cost. Therefore, frequency response in not that meaningful especially when considering the room effects, but we have included some measurements to give an idea of the natural response especially around the lower cut-off.

3D printing

The enclosure is printed in one part (234 mm diameter) and takes approximately 1.5 kg of filament. Print time is about 48 hours. The mass can be increased by lining the walls with sound deadening mat. Although the external wall is spherical, there is a cylindrical inner wall that braces the woofer to the passive resonator and, thanks to a single curvature surface, allows easy installment of thick sound deadening mat. The drivers are fastened using 4.2 mm wood screws. There is a geometry file for a gasket for the woofer which can be printed from TPU. Traditional gasketing methods will work, but the 3D printed gasket is seamless and has the screw hole pattern accurately incorporated. The binding posts are recessed deep into the enclosure and only accept banana plugs in that configuration. An O-ring under the binding post washer is recommended and there is a chamfer for it. 3D printing using a wood-filled filament allows easy sanding for a smooth surface finish. The photos show 15 minutes worth of post-processing making this a very easy and fast build without compromising in function and looks.


Sound quality

The subwoofer was compared to the much larger, THX certified Logitech Z623 subwoofer. The sound is very similar, but in a much smaller package. The SW2 is a great companion for small satellite speakers and brings fullness to the bass. Electronic music will benefit from the “boom” offered by this small unit, while other types of music may require turning down the level a bit for a tighter bass.

Links and video

The 3D files can be found in Etsy store:

Please support us by using the affiliate link below just before ordering the components:

TangBand W5-1138 on

Dayton Audio DSA175-PR on

Arylic 2.1 BT amp on

Technology 3D printing Audio DIY Loudspeaker Speakers

3D printed active subwoofer – SW1

Our 3D printed full-range speakers needed something to beef up the lower end of the frequency spectrum. We set out to design a compact subwoofer that can be used together with our FR3 speakers. The result is a 13 liter enclosure with a 6.5″ driver, a matching passive resonator and a plate amp. The passive resonator allows tuning the resonance frequency to match room modes, for example. The plate amp can power satellite speakers and has a fixed high-pass filter. The low-pass cut-off frequency for the subwoofer can be adjusted and the level too, which means that this system can be easily mated with signal sources that do not have equalizing or DSP capabilities in themselves.

3D printing

The enclosure consists of two parts, which are glued together after printing. Total print time is about 100 hours and uses about 4 kg of filament. Support is only needed for the small recess where the plate amp is mounted. Dual-material printing is not needed. The mass of the enclosure can be increased by filling the walls with epoxy through the holes in the back. A geometry file for 3D printing a matching funnel is provided, too. 2 kg additional mass can be obtained this way.

The 3D files can be found on Thingiverse for free:

Please support us by using the affiliate link below just before ordering the components:

Dayton Audio DSA175 on

Dayton Audio DSA175-PR on

Lepai LP210PA amp on


The video below explains the concept in more detail.

3D printing Audio DIY Loudspeaker Speakers Technology

Full-range desktop speakers – FR3

Metal-filled filament and internal support add significant mass and rigidity.

The first version used internal ribbing and bitumen paint to reduce enclosure resonance. The second version used an external carbon fiber shell. Both approaches were a bit cumbersome. For the third version we wanted to fully use the capabilities of 3D-printing. Therefore, a high-density metal-filled filament was used and internal gyroid-shaped support was used even where overhanging surfaces would not have required it. In addition, height and tilt can be adjusted using three threaded rods that form a tripod. The finished enclosure with three 14 mm trapezoid-threaded nuts bonded to it weighs 1.2 kg.

Please support us by using the affiliate link below for ordering the Dayton Audio RS-100 drivers:

Audio 3D printing Carbon fiber DIY Loudspeaker Speakers Technology

Exotic carbon fiber skinned loudspeakers with excellent stiffness – FR2

Additive manufacturing

Using additive manufacturing (AM) has many benefits over traditional construction methods, such as design freedom, fast product development and integration of functions into one part. There are drawbacks as well. The plastic AM parts tend to be low in mass and not very stiff. Air-tight walls are sometimes difficult to achieve, too.  Adding mass by increasing fill density of the print is not a good solution, since it adds build time and material cost. Stiffeners and bitumen paint were used in (Version 1). However, the stiffeners were cumbersome to paint with bitumen and it did not add significant weight. For Version 2, we used the vent as a part of the mechanical structure and used a thicker wall. But some additional means were needed to bring 3D printed enclosures on par with traditional cabinet materials.

Carbon fiber in loudspeker building

Dry carbon fiber tow was wound around the enclosure and then wetted with epoxy resin. The composite skin was sanded after curing and additional coats of epoxy were added. The result is a unique unidirectional carbon fiber surface finish. The composite shell adds mass and stiffness to the enclosure. The loudspeaker sits on four feet printed from TPU material, which allows rotating the speaker.

Make them yourself

The following changes were made to Thingiverse:

  • Updating the driver dimensions and screw pattern to the latest Alpair 7 MS.
  • The weight of the loudspeaker will try to bend the speaker stand. It was therefore changed from a shell-like structure to a solid.

If you plan to order the drivers, please support us by using the affiliate link below:


Audio 3D printing DIY Loudspeaker Speakers Technology

Clean sound and rich detail with full-range speakers – FR1


The first version of #3D-Fi speakers are spherical (180 mm diameter) full-range loudspeakers with 3 liter internal volume. The box is vented with two rectangular ports on both sides. The ports act as stiffeners and also give more space to assemble the connectors and amplifier inside the enclosure. Internal wall stiffeners are used in order to maximize internal volume as opposed to simply increasing wall thickness, since a small external size is typically desired while internal volume needs to be high enough for the driver to work properly. We use bitumen paint to both seal the enclosure and also to add mass. The enclosure is printed as one part using UPM Formi3D cellulose composite filament. Metallic nuts are pressed on the backside of the flange to receive the machine threaded screws that hold the emitter.


Our setup uses a laptop PC as a source which allows equalizing the frequency response at the digital source. The signal is transferred via USB to a USB-powered DAC/pre-amplifier with volume control and a power switch. The analog signal is then transferred to one of the speakers where it is amplified using a two-channel chip amplifier board that is powered by a 65 W laptop charger. The amplified signal of the other channel is then transferred to the other speaker for reproduction. The design uses 6 cm full-range emitters without any analog filters or corrections.

The design was updated for Thingiverse:

  • Machine screws and nuts replaced with 2.5 mm hole for wood screws
  • Fully passive design without the amp. Instead, 4 mm holes for binding posts only
  • Sealed enclosure

If you like the design and plan on building one yourself, please support us by using the affiliate link below for ordering the components:

MarkAudio Alpair 6 on


A reference system with Genelec 8040 speakers was used for comparison. The sound of the 3D-Fi speakers is very unique and quite tricky to get the most out of. The full-range emitters are very sensitive to off-axis listening and the listening distance also changes the sound markedly. Even slightly tilting one’s head has an effect. It seems that finding the best spot is challenging and takes time. It’s hard to remember not to move an inch while listening to these speakers. However, all the effort pays off, because there is a reward at the end. The sound stage is unbelievably good and there is a huge presence from such a tiny speaker. The Genelecs sound distant and all over the place compared to the very precise and point-like sound of the 3D-Fi speakers. Obviously the bass is not very deep and the sound pressure levels achievable with 6 cm cones is limited. On the other hand, they seem to tolerate significant bass boost without distortion and in normal listening the cone travel stays in check. Overall, a very difficult set of speakers to get into and they are quite picky with the type of music played, but once a good recording is found together with the right listening conditions…Bliss!

Acknowledgements: We wish to thank UPM for the materials and support. J-P Virtanen took the studio pictures and Markus Markkanen the ones in the library.