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3D printing Audio DIY Loudspeaker Speakers Technology

Passive Mini-subwoofer – SW2

Very low enclosure resonance thanks to spherical shape and sound deadening mat.

Concept

Our previous 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 5″ long-throw driver and the same passive radiatior as in the SW1. The enclosure is now only 5 liters and much easier to place on the desktop. The passive resonator allows tuning the resonance frequency to match 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.

Measurements

The measured resonance frequency of the passive radiator indicates that some air-coupling occurs. 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 avoid room modes. Practical lower roll-off frequency is 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 knee.

Fabrication

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 inside wall that braces the woofer with the resonator and, thanks to single curvature surface, allows easy placement of thick sound deadening mat. The drivers are fastened using 4.2 mm wood screws and there is a geometry file for a gasket for the woofer which can be printed from TPU. Traditional gasketing methods will work obviously, too. 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. Wood-filled prints can easily be sanded for a smoother 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

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:

https://www.etsy.com/shop/RDPhysics

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

TangBand W5-1138 on SoundImports.eu

Dayton Audio DSA175-PR on SoundImports.eu

Arylic 2.1 BT amp on SoundImports.eu

Categories
3D printing Audio DIY Loudspeaker Speakers Technology

Active Subwoofer – SW1

Very low enclosure resonance thanks to the epoxy-filled walls.

Our 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 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. The mass can be increased by filling the walls with epoxy through the holes in the back. 2 kg additional mass can be obtained this way.

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

https://www.thingiverse.com/thing:4802531

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

Dayton Audio DSA175 on SoundImports.eu

Dayton Audio DSA175-PR on SoundImports.eu

Lepai LP210PA amp on SoundImports.eu

Categories
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:

SoundImports.eu

Categories
3D printing Audio DIY Loudspeaker Speakers Technology

Full-range desktop speakers – FR1

The cellulose fiber reinforced thermoplastic used is from renewable sources and can be recycled.

Construction

The first version of 3D-Fi speakers are spherical (180 mm diameter) 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 SoundImports.eu

Sound

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.