Hi there,

Here is a Bluetooth speaker I've made some time ago. It consists of 1 x 18650 li-ion battery (usually lasts for 2 evenings filled with music at moderate volume), Bluetooth audio module, a USB charger module and a tiny PAM8403 audio amplifier with a potentiometer. The speakers are the most expensive parts of this project - I've chosen BF37 due to their good bass response (for their size) and generally high sound quality. The housing volume is around 0.9 L which follows the simulation by WinISD. The membranes of the speakers are protected by a 40mm fan metal covers (a little bit bent to match the speaker screw hole spacing). My intention was tu use the PCV pipe, but to be honest - I was too lazy to cut pipes and drill holes, so I decided to 3D_print the enclosure entirely.

After assembling all together I realized that the unwanted noise is clearly hearable at absence of the sound - the reason was a ground loop problem. To get rid of it I had to apply an electrical modification to the bluetooth module as well as the audio amplifier. Right now - I'm 100% happy by the results I've obtained. The sound is pleasant, with no frequency peaking and remarkable noise and distortion.

The interior of the spaker is filled with kind of syntetic wool.

Although I'm happy with the sound, I consider the project of a housing as far from perfection due to difficult assembly. Keep it in mind if you want to replicate my speaker :)

Last word: BF37 speakers are truly amazing, but they are way too expensive. They require almost hermetic sealing - the only holes are due to bass reflex pipes. If the sealing is not perfect, the bass disappears - so take care of sealing and appropriate 3D print precision to avoid disappointment.

Cheers!