On a scale of 1 to 3, this project ranks a 2 in difficulty. You'll need to be able to solder, desolder, identify a few components and adapt this design to suit your application.
My out of pocket costs were $6. The plastic, speaker, zip ties, misc. wire were either found or leftovers from other projects.
~1 hour once you have all supplies
From an appearance stand point - I give it a 9 out of 10
From a functionality stand point - I give it an 8 out of 10
From an audio stand point - I give it a 6 out of 10
From a loudness stand point - I give it a 7 out of 10
(A prior version of this would have had scores under 5)
As a side note - yes, this is technically not a stereo. Complaining about that is your prerogative, but I couldn't care less. If I say sharpie, you know it's a permanent marker - communication has been served.
Step 1: Materials
1 Power Supply
*$5 Harbor Fright Megaphone
*Free speaker from discarded boombox
*Batteries, AA's are fine - they need to put out ~6V (I later used a 6V gel cell) - you can also use the original battery pack if that suits you
*Wire, some wire came from boombox - I also used a Cat5 cable
*Headphone jack can come from a pair of headphones
- For the mount, I used a piece of plastic that I then laser cut to fit perfectly into my bike rack - feel free to improvise, similar quality can be had using thin plywood and a jigsaw ;)
Step 2: Disassemble and Modify Megaphone
You'll need to desolder the microphone and then solder on a bit of wire - the length of which is based on how far your music player will be from your speaker.
Solder the headphone jack to the opposite end of the speaker.
At this point, you should be able to play music through the megaphone's original speaker.
Step 3: Remove Old Driver - Replace with new speaker
Replace with another speaker - I sourced mine from a derelict boom box.
Check that you can still play music - this is also a good time to mock up mounting locations.
Step 4: Cut mounting board
And, while I was at it, I laser etched and painted my crest for a little extra personalization. By raster cutting at l medium power levels while keeping the protective paper on, you can create clean looking paint by laser graphics. By etching, then painting, then etching the paint off, you can easily create multi-colored and multi level graphics with laser precision.
Step 5: Mount Hardware
The second picture shows the plastic spacers used to interface with the boom box speaker's mount. Also notice the zip tie holding the blue cat5 cable to the circuit board to serve as strain relief in the event the cord should ever get tugged on. This turns out to be absolutely necessary.
The circuit board is mounted to the speaker on one of the machine screws.
Step 6: Mount To Bike
I'm using zip ties because
b) Don't Corrode
d) Are available in the reusable variety
e) Lots of colors