While the sound level that comes from a speaker headset is not exceptional (as it is designed to be next to your ear), they still make for a good little speaker for an old iPod or mp3 player without its own speaker.
The speaker fits easily in your pocket and is a nice little companion for your iPod or mp3 player on those days out and about.
Step 1: Collect the Parts and Tools
1x Headset (I used one out of a phone headset which also had a microphone)
1x Film Canister
Dremel / rotary cutting tool (or you could use a hand saw if you have neither of the before mentioned)
Selleys Knead It multi-purpose putty (or similar) OR bluetak
Step 2: Dismantling the Headset
2. Remove the foam over the speaker
3. Since my headset had a microphone, I had to remove the microphone cable which was attached to the speaker cable so I was just left with the headset speaker, cable and 3.5mm jack
4. Cut the actual speaker out of the plastic which surrounds it using a rotary cutting tool or a hand saw.
Step 3: Assembling the Speaker
2. In my case the speaker was slightly too small to fit in the canister and needed to be given a wider casing to sit in the canister. Using Selleys Knead It (a putty which once the two parts are mixed becomes as hard as a rock within half an hour) or bluetak if you don't have any putty, wrap the speaker so that it is wider all around.
3. Gently work the speaker in to the canister until it is low enough to allow for the lid to be placed on it later. Clean up the putty to look neat and remove excess amounts.
4. Once you are happy with the speaker's position, slide the headset cable in and out of the putty to widen the hole which it is slotted through so as to allow for the cable length to be adjusted once the putty has set. (This is allowed by the fact that there is some extra space under the speaker, despite the cable being 1m long)
5. Cut a slit in the lid of the film canister to allow for the cable to come through when the speaker is closed up
Step 4: Finished
I'm sure there is plenty of room for improvement but the speaker does the job and fits nicely in the pocket.
For the speaker, any small magnet speaker would work (could grab one out of a computer etc.) and then you would just need to solder on a 3.5mm headphone jack from an old pair of headphones or speakers.
I was thinking you could buy a retractable headphone jack and then the cable would automatically retract once you were finished with it so you don't have to feed the cable back in to the canister after using it.
Also, the design could be built on with the use of an amplified battery powered speaker for better sound quality and sound level.