Project 12 – Build a DIY loudspeaker.

1. Preparation: Barrel to make the cabinet (box), Sonos speaker drivers, trebles, amplifier, batteries, on of buttons.
2. Assembling: Cabinet :Drill 2 1,25-inch (radius) holes for two full-range Sonos drivers (speakers).Drill 2 1-inch (radius) holes for 2 passive bass radiators.* The speaker’s diaphragm would vibrate during its operating, which means that the capacity of the space inside the cabinet would change rapidly, which means air within the space would be compressed and expanded rapidly, which prevents speaker’s diaphragm from vibrating normally. Because of this, I drilled 2 holes on the back of the cabinet, and then installed two passive bass radiators so that damping has been decreased significantly, the passive bass radiators has been vibrated, which meant the bass quality has been improved a lot.

• Drill 8 little holes to screw 2 Sonos drivers (4 holes for each).Drill two 2cm (radius) holes for two additional treble drivers (speakers), these drivers would be glued instead of screwing.Drill 4 small holes on 4 edges to screw 2 handles.Drill 16 tiny holes to screw the lockerUse gasket (padding, tape) below the lid to ensure after closing, no air would be passed out, so that the sound of bass is more powerful.

• Battery, on/off button, charging port: Connect the battery in series of five to increase the voltage from 3,8 volt, 3000mAh each cell to 19 volts, 3000mAh in series. I made the same series and connected both of them in parallel to increase the capacity from 3000mAh to 6000mAh.

• On/off button:
  • Connect positive wire of the battery pack to one side of the button, and another side would be connected to the positive power supply port of the amplifier and the led indicator of the switch.
    • Connect negative ports of amplifier, battery, and of the led indicator of the switch directly.

• Amplifier and Speakers:Amplifier: Glue amplifier inside the barrel

• Speakers (Drivers): Use copper wires to connect amplifier to speakers. Two speakers (a full range one and a trebble one) on the same side would be connected to the same port.

• Treble: On the positive side (1), connect the capacitor in series to filter the low frequency (2), which also contains high power and could damage the treble drivers.
  • (1): Reason why there is positive and negative side on speaker which using alternating current (AC): because manufacturer doesn’t want different drivers to be connected in different order, because this could lead to phase cancellation, frequencies cancellation, or unmatched sound between different speakers on the same side or in stereo.
  • (2):

Xc stands for capacitive reactance, f stands for the frequency of the AC source, c stands for capacity. According to this formula, the lower the frequency is, the higher the capacitive reactance will be, and vice versa. Therefore, a capacitor can be used to stop low frequency current.