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.

Audio 3D printed 3D printing Carbon fiber DIY Loudspeaker Speakers Technology

Six reasons 3D printed spherical loudspeaker enclosures are popular


It is striking how often 3D printed speakers take the shape of a sphere and that is also how RD Physics started with the FR1 full-range speaker. What are the benefits of spherical loudspeaker enclosures and why are they so popular?

  1. Rigid and void of panel vibrations
  2. Minimum material use for a given volume
  3. Potentially avoid edge diffraction
  4. Omnidirectional up to a relatively high frequency and controlled baffle “step”
  5. Aesthetically pleasing with a single circular driver
  6. Difficult to manufacture any other way than 3D printing

As RD Physics has extensive experience in these types of enclosures, we have decided to share our learning in one blog post. The models are presented in chronological order allowing the reader to understand the development that took place over the years of building and listening to various versions of the FR. Most of the designs are offered open-source to the community.

FR1 – Full-range bliss in a compact form

The FR1 is a spherical (180 mm diameter) full-range loudspeaker with a sealed enclosure. Internal wall stiffeners are used in order to maximize internal volume as opposed to simply increasing wall thickness, which robs internal volume. We use Noise Killer paint to both seal the enclosure and also to add mass and damping. The sound of the FR1 speakers is very unique and quite tricky to get the most out of. The full-range emitters are very directional and the listening distance also changes the sound markedly.

ModelRD Physics FR1
DriverMark Audio Alpair 6M 2.5″
Enclosure3 liters sealed
MaterialUPM Formi3D
ConstructionInternal webbing with Noise Killer damping
TiltFixed at 15 degrees

FR2 – Exotic carbon fiber skin reduces resonances

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 the 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 FR1. However, the stiffeners were cumbersome to paint with bitumen and it did not add significant weight. For FR2, 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 loudspeaker 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 rotation.

ModelRD Physics FR2
DriverMark Audio Alpair 7MS 3″
Enclosure5 liters vented
MaterialUPM Formi3D + CFRP
ConstructionStructural port and carbon fiber skin
TiltTPU feet allow tilt ~0-15 degrees

FR3 – Metal-filled filament for mass and rigidity

The FR1 used internal ribbing and Noise Killer paint to reduce enclosure resonance. The FR2 used an external carbon fiber shell. Both approaches were a bit cumbersome and laborious. For the third version, we wanted to fully use the capabilities of 3D-printing. Therefore, a high-density metal-filled filament was used an 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. The RS100 drivers have a distinct on-axis peak at the upper treble, which actually works nicely for those who like a bright sound. Those who don’t should toe-in the speakers a bit.

ModelRD Physics FR3
DriverDayton Audio RS100 4″
Enclosure2 liters sealed
MaterialColorfabb steel fill
ConstructionGyroid infill as an internal stiffener
Tilt14 mm leadscrew tripod

FR4 – Refining the concept further

The metal-filled filament used in the FR3 was too brittle and difficult to post-process. The FR4 uses wood-filled filament, which is more ductile and easier to sand if needed. 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. 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 complement the lower frequency spectrum.

ModelRD Physics FR4
DriverTangband W3-1878 3″
Enclosure1 liter sealed
MaterialAddNorth Textura
ConstructionGyroid infill as an internal stiffener
Tilt12 mm leadscrew tripod

FR5 – Returning to square one

Reviewing the FR project so far, we came to the conclusion that all things considered, the original FR1 is the DIY project that was the most fun to build and listen to. It’s simple but rewarding once dialed in. For the FR5 we went back to basics by ditching the tripod and returning to a simple white spherical enclosure. The tilt adjustment is handled by a TPU mounting ring that allows a large adjustment range. The Scan Speak 10F driver is one of the best for voice reproduction, but our subjective view is that it needs a tweeter in addition to a subwoofer making it suitable for three-way builds only.

ModelRD Physics FR5
DriverScan Speak 10F 3″
Enclosure2 liters sealed
MaterialAddNorth Textura
ConstructionStiffeners and alu-butyl sound-deadening mat
TiltTPU ring +-30 degrees

3D files and components

In the table below you’ll find links to the drivers used in each version as well as the geometry files needed for slicing the toolpaths. Support us by clicking on the Soundimports affiliate links before buying anything from them (we get a small commission and it won’t cost you a dime). Thank you!

ModelComponents3D files
FR1Alpair6M at SoundimportsFR1 at Thingiverse
FR2Alpair7MS at SoundimportsFR2 at Thingiverse
FR3RS100 at SoundimportsFR3 at Thingiverse
FR4W3-1878 at SoundimportsFR4 at Etsy Shop
FR510F at SoundimportsFR5 at Thingiverse



We wish to thank UPM for the Formi3D materials and support. Photos taken by J-P Virtanen and Markus Markkanen. Erell Bodinier handled the carbon fiber skinning.