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How a DIY Bluetooth speaker kit works
A speaker kit is a small lesson in physics wrapped in a plywood box. Here is what each part does, how the build goes on the table, and the one mistake worth avoiding.
The three parts that make sound
The amplifier board receives music from a phone over Bluetooth and boosts the signal. That stronger signal travels down two thin wires to each driver, where it flows through a coil sitting next to a permanent magnet.
As the current changes direction, the coil is pushed and pulled against the magnet, and the paper cone attached to it moves the air. Those tiny movements, hundreds of times a second, are what you hear as music.
Setting up the build table
Clear a table, lay a tea towel down so screws do not roll away, and sort the plywood sheets, drivers, board, battery box and wires into groups before starting. Read the first two pages of the picture guide together.
Pop the panels out gently. If a tab resists, wiggle it rather than forcing it, because plywood can split along the grain.
The one wiring rule
Red and black leads from the battery box must never be joined to each other. The guide marks this clearly, and it is worth saying out loud before the connectors come out: red goes to the red marking on the board, black to black, and that is all.
Push-fit plugs only go in one way. If a plug does not slide home easily, turn it over rather than pressing harder.
First switch-on
Insert four AA cells, flip the rocker switch and look for the speaker in your phone's Bluetooth list. Start the volume low, then turn it up as the builder grins.
If there is no sound, check the driver plugs first and the battery orientation second. Those two points solve nearly every quiet speaker.