DIY Underwater Yoghurt Pot Speaker Build

2022-10-11

To help create some of the dark and mysterious textures in the videogame Silt I used a slightly unusual technique: playing sound underwater and re-recording it.

🎬 The underwater speaker in action

Whilst I had a pair of hydrophones, I didn't have any underwater speakers. Unfortunately the commercial solutions to this weren't cheap and didn't really match my requirements. I needed a small, hand-held speaker that I could move silently through the water to create spatial effects. The solution was to make my own using some old cable, a yoghurt pot and a cheap water-proof speaker driver. It didn't need to be particularly hi-fidelity as the aesthetic for the game is quite textured and distorted.

You can hear in the video how moving the speaker causes spatialisation, which combined with additional effects and processing gives a very large sense of space. For Silt I wanted to capture a sense of blurred fragments of distant sounds drifting in on waves, contrasting them with very close sounds in the divers immediate proximity to give a large front-to-back depth in the image.

Disclaimer

Please Note: Should you choose to make your own speaker using these plans, I am not responsible for any damage caused to yourself nor your equipment, your home etc. etc.

What You Need

Here's a photo of some of 📷 the tools needed for the build

Parts

Tools

Build Guide

1) Measure out the hole for the speaker driver on paper using a compass. This will be used as a cutting template. The dimensions needed will be in the speaker datasheet.

📷 A circle drawn onto paper to form the cutting template for the speaker driver to be mounted

2) Cut-out the paper template and glue it to the yoghurt pot lid, dead centre.

📷 The cutting template glued onto the yoghurt pot lid


3) Cut the hole using a small, sharp knife or whatever the best tool you have to do this with. It goes without saying to do this as safely as you can, with as little force as possible. It doesn't have to be 'perfect' as it will be hidden by the speaker driver surround, just get it close.

📷 The lid with the template cut out


4) Place the speaker driver into the newly cut hole. Hopefully it should fit correctly. If not, try and correct your mistakes or you've got more yoghurt to be eating.

📷 The lid with the speaker driver placed inside it


5) Hold the speaker in place and poke the awl through the screw holes to mark where they will go. Then use the awl to make small pilot holes. The speaker can then be mounted to the lid by gently driving the screws through the holes and locking them to small bolts on the underside. The screws I used were some pretty cheap (and pretty crap) plastic standoffs for pcbs.

📷 The underside of the speaker driver showing the screws poking through the holes


6) With your speaker driver attached to the lid it should look something like this.

📷 The underside of the speaker driver showing the screws poking through the holes


7) Once you're confident with the speaker mounting you're ready to use the glue gun to seal the edges as much as possible. Anywhere you think water might get through, stuff-up with glue.

📷 This close-up shows some the glue around the underside of the speaker driver. Messy but functional


8) Use the awl to make a pilot hole and then drill a hole in the bottom of the pot that matched the gauge of the speaker cable. Try and get it as snug as possible without it stripping the cable.

You could place the cable hole in the side of the pot if you prefer

📷 The speaker cable hole in the underside of the yoghurt pot


9) You can now run the cable through the pot and solder it to the speaker driver. Seal around the speaker cable with the glue gun or silicone.

📷 The soldered speaker, foam strain relief and yoghurt pot ready to be mid-assembly

In the photo you'll see that I also added a small ring of polystyrene like packing material. The reason for this is act as a bit of a strain relief for the soldered joints. I then filled the yoghurt put with bubble wrap to act as internal damping and try to reduce some of the resonance inside the (yoghurt pot) speaker cabinet. I'm not sure really what effect it has (I didn't measure a comparison), but I figured it wouldn't hurt.

A later addition was to add another piece of foam/polystyrene under the pot, around the speaker cable entry point to provide additional strain relief.

📷 Foam strain relief on the underside of the pot. You can see the pot is filled with bubble wrap


10) The final step is to glue the lid shut from the underside. I also filled this with silicone sealant to prevent any water leaking in. I also added some additional sealant around the rim of the speaker driver and into the screw holes.

📷 Glue and silicone sealant to keep the lid fixed to the pot and prevent water entering

11) The final final step, is to have somewhere to actually record things. I used an aquarium which I placed inside a plywood box I constructed and sealed with silicone sealant (I didn't fancy 100 litres of water emptying itself into my studio in the middle of the night.)

📷 Glue and silicone sealant to keep the lid fixed to the pot and prevent water entering

In Use

To power my speaker I used a cheap Nobsound amp. It needed to be driven quite hard but it was effective enough for what I needed. To be honest, the performance wasn't great and I suspect it wasn't a decent match for my speaker. To clean-up some of the hum and noise from the speaker as well as some of the resonance of the hydrophones I used RX spectral denoise.

No doubt that with more time and budget, higher fidelity results are possible, but for what I was looking for sonically, this cheap approach worked well and produced some great sounds that I used in Silt.

Silt is out now on PC and consoles:
Steam / Nintendo Switch / PS4 & PS5 / Xbox / GOG / Epic Game Store

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