DIY Electro Acoustic Kalimba

In late October we decided with my class to do a secret Santa event. It was decided that DIY gifts were strongly encouraged, which imho was a really great idea. After randomly assigning a secret Santa to everyone, I discovered that I had to make a gift for a good friend of mine that happen to be a big music fan. I immediately thought about building some sort of instrument. In addition, this friend is quite interested in microtonal music, which meant I had to build an instrument he could easily tune (or detune) at his will.

That’s why I chose to build a Kalimba and just for fun, I added the possibility to amplify its signal.

Here is my process building it, however I want to thank before everything CRI’s MakerLab, the best FabLab I know (the only one I know in fact), for providing their help and tools

Material

• 30 × 30 cm plywood 5mm
• 12mm wide and 8 cm long piece of copper pipe
• 16 cm of 3mm wide metal rode
• 40 × 80 mm steal plate 0.75 mm
• 2 × 25mm long 4m bolts
• 2 × 4m washers
• 2 × 4m T-nuts
• a piezo disk contact mic
• a bit of wire
• a female jack connector

Tools

• a laser cutter
• sanding paper
• a set of wood and metal files
• a drill press
• a metal saw
• a metal shear

Laser cutting the box

Cut the design out of 5mm plywood.

The box was designed with MakerCase (https://www.makercase.com/), then I added the bridge, soundhole and engraved details. You can find the svg file here, but you may have to adapt it for the specificity of the laser cutter you have access to. You can also personalize it : the black graphics only have an aesthetic goal.

The edges of the lasercut pieces will be covered of dirty black soot so clean them using sandpaper.

Gluing the lasercut parts

Start by gluing the lower, bottom, front and side parts of the kalimba’s box.

Add PVA glue between the edge slots of the lasercut parts. Then clamp the parts together and wait for the glue to set.

Cutting and drilling the copper pipe to size

Using a metal saw, cut a piece of 12mm wide tube to a length of 8 cm.

Then file the cut edges to make them less aggressive.

Drill 2 × 4 mm holes on the piece of tube with a drill press 5mm away from the edge of the tube.

Cutting the metal rodes

With a metal saw, cut 2 × 8cm of 3mm wide metal rode, then file the cut edges

Filing the the bridge

With a half-round file, dig the bridge piece of wood at the position where the copper tube is going to be.

With a smaller file, dig two slots for the two metal rods

Add threaded insert on the bridge

Insert two t-nuts in the two holes of upper plate of the kalimba and fix them with a hammer.

You may have to file those holes for the t-nuts to fit in them

Fix the bridge on the front of the kalimba

With two 4mm bolt and washers, fix the metal tube on the bridge wooden piece and on the front wooden piece of the kalimba.

Don't forget to add PVA glue between the the bridge and the upper piece before bolting everything.

Soldering the piezo element to the female jack connector

Wire one of the piezo mic’s connector to one of of the jack’s connector, and the other two connector together. If you’re not familiar with soldering, try to get your hand on piezo elements that already have connecting wires, as it can be difficult to solder on the ceramic part of the piezo.

Stuffing the kalimba with the electronics

Screw the jack connector in the bottom part of the box. Be careful not breaking the connection if you did a poor soldering job.

Then glue the piezo element on your box.

Here, there is a lot of experimentation to do as the placement and type of glue used will have a big impact on the sound you’ll get from the mic. If you want more information, look for the cigar box guitar community online, they have a lot of experience with contact mic which is useful because this is more an art than a science.

Personally, I ended up gluing the contact mic on a ≈1 mm layer of hot glue. This filter the high frequency vibration, but in my case, maybe a bit too much. If you have time, try to test different position before fixing your mic.

Gluing the upper part of the kalimba

At this stage it can be useful to add another layer of glue if your first attempt at gluing the lasercut part left some holes between the edge slots.

Sanding

Sand the kalimba to remove the excess of glue then varnish the kalimba. This stage can change a lot the sound of the kalimba so be careful.

Cutting the steel tines

Using a caliper, mark 7 4mm wide and 80mm long parallel lines on the steel plate.

Cut the plate with a metal shear following these lines.

Then flatten the steel tines by clamping them to a flat piece of wood

Filing

File the steel tines to round their edges and particularly the part of the tines that you’re going to touch while playing the kalimba.

Mount the steel tines on the bridge by sandwitching them between the metal rods and the metal tube you attached to the bridge.

Once your kalimba is finished, you can start jamming.

I'm really happy with the look of my kalimba, however the sound is not perfect, to say the least.

You'll find below a recording of the kalimba amplified through a guitar amplifier.