Loudspeaker gets mounted into an empty coconut shell. Second life for the shell, improved sound from the speaker.
Step 1: Gather Materials
One speaker. 2" dia, which I was using to listen to the output of a few experimental audio amplifiers intended for alarm and warning sounds. Volume was more important than fidelity, so some sort of a resonant enclosure was indicated. It measured about 7.5 ohms with my HiOki digital meter.
One coconut shell. In two halves, with a clean break and no pieces missing. Large enough to accomodate the speaker inside.
One more half shell (optional) for the base, if you do not want your enclosure to roll off the desktop.
Step 2: Drill Out Eyes
I drilled out the half with the three 'eyes' for the sound. The result looked like a face, so I enlarged the mouth a little bit more.
Step 3: Fit Bracket for Electronics
The other half was drilled to accept a bolt and nut to hold a bracket made of tin sheet which might hold a circuit board inside.
Step 4: Fix the Fabric to Keep Insects Out
I glued in a piece of acoustically transparent fabric, and checked the fit of the speaker.
Step 5: Fix the Speaker
A mounting hole was cut in the back half of the shell, and it was fixed to the base with a nut and bolt.
I used a two component epoxy filler to seal the gaps around the speaker. Since the shell is not perfectly round, air can leak around the sides of the speaker and this will lead to a loss of volume. I used a plastic bag to isolate the speaker from the sticky compound so that the cone would not be contaminated.
The filler will have to be cut away if the speaker ever needs to be replaced. But then it might be easier to make a new enclosure, because the replacement speaker might not be of the exact size as the old one.
Step 6: Solder on Wires and Test
Since I was using a third half shell as base, I decided to put any electronics in the base where it will be more accessible. So the bracket was not used.
A piece of twin flex peeled from a computer ribbon cable was used to connect to the speaker. It is led into the bottom through holes drilled for the purpose.
A cell (1.5 V) applied to the wires resulted in the production of clicking sounds, significantly louder than when the speaker was used in the open.
The two halves making up the enclosure was cemented together with synthetic rubber adhesive after testing. This results in an airtight seal.
No sound absorbing materials are used back of the speaker since the intent is to have a resonating chamber there. The reproduction will be decidedly 'peaky' with some frequencies emphasised. This is acceptable since the device will be used for alarm beeps and announcements.
A hifi version could be made, but I think a large enough coconut might be mighty hard to find, as well as to break in a clean way as required for this enclosure.
It does look like a face, with a pronounced expression. You could have a trio with 'see no evil', 'hear no evil' and 'speak no evil'.
The first will have no eyes. The second will have no ears. The third will have no mouth, and will house the stereo amplifier.