Instructables
video DIY BIKE SPEAKER
What you need:

DIY Speaker Kit 
2x A3 Foamboards
5x M4 or M5 bolts
15x M4 or M5 Nuts
20x washers
5-6x Rubber Bands
5-6x Long cable ties



Instructions:

1.Measure the frame of your bike
2.Cut the Foamboard with 2-5cm clearance between the edge of the foam board and the bike frame
3.Punch or cut holes on each corner of the foam board
4. Repeat the procedure for the second piece of foam board

5. Cut holes for the controls of DIY Speaker amplifier and secure it to the foam board using the nut of the potentiometer

6. Place nuts with washers to protect the foam board on both sides of the foam boards to hold it in place
7. Secure all sides of the board using the nuts and bolts
8. Once the foam board structure is done feed the rubber bands around the bolts and clip them using the cable tie to the bike frame
9. Repeat step 8 until all sides are secure.

10. Attach the amplifier to the foam board and turn up the music!