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:
- Finish the outside of the enclosure and make sure the driver and SpeakON connector fit.
- Line the inside with bitumen damping material and fill it quite densily with wadding.
- Solder wires to the speaker drivers and crimp fastON connectors at the other end. Mark woofer and tweeter positive and negative wires.
- Feed the wires through the SpeakON connector opening and mount the driver using wood screws. Use gasket/adaptor if you have the SEAS driver.
- Connect the fastON connectors to you SpeakON connector and mount it.
- 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.