I wanted to construct a portable iPod speaker for when I was outdoors, possibly building something in my backyard, or even down the beach (without the need for a power outlet, or endless supply of batteries...) Up until now, when I have been in my backyard, I have had to fumble around with a stupid extension cord, run it out into the yard, plug in an old stereo and hope for the best. Even then, I get some music, but also ads... ads make me sad...
I decided to build myself something, as anything store-bought is simply a waste of money (and no fun!)
2 x 4" 16ohm speakers, gutted from a pair of Sanyo stereo speakers someone gave me on their way to the bin...
1 x 30 callibre ammunition box (bought from a displosal store for $7.95, not emptied by me on various people of choice)
1 x 3.5mm / RCA cable, with RCA plugs cut off, and wires stripped and treated
2 x 4" speaker grille covers with brackets
Various hardware, nuts and bolts, screws and washers that I had bought previously in a mixed packet from a hardware store
Step 1: Measuring and cutting the holes!
Okay, by far, the toughest part of this project is cutting the holes for the speakers into the tin.
First, I decided on cutting the holes a little smaller than 4", as I was originally going to have the grilles mounted internally... however the tin proved rather tough, so the holes were a little sloppy and sharp, so mounting them externally managed to cover up this mishap, and also helped it look a bit more awesome...
Make a template on paper, so the layout will be accurate, level and neat. Use a compass or something that is close to the right diameter, and draw the speaker shape onto the paper. I cut my paper to the size of the side of the tin, folded in half to find the centre, then in quarters to find the centre of each half. I lined the circle to this, then traced it on. You might notice a fold in the middle... This is due to the speakers coming too close to the edges of the tin, which would make the mounting a bit too difficult, so I crimped the paper i nthe middle to bring them in closer... Make sense? :D
Once the template is transferred to the tin, it is time to cut it out!
This involves pre-drilling for using a jigsaw / scrollsaw to cut the holes as neatly as possible into the tin. PLEASE use ear protection!! My ears are still ringing from it all, and its been 12 hours now... seriously, it's loud!
Step 2: Holes cut, mounting speakers...
This might seem like a big jump forward, but once the holes are cut, the next step is to mount the speakers.
Holes have been drilled for their mounting (I skipped that, as if you don't know how to drill a hole, you shouldn't be on this site!) :D
As the metal has sharp edges, I decided to add some room for the speaker, so as not to cut or tear the cone (oh noes, $2.50 of speakers ruined!!) This spacer was as simple as adding another not in front of the speaker. This allows air movement, as well as some ventilation, which I will get into later...
It is hard to see, but from the front of the box, I have placed the bracket to hold the grille in with, the screw goes through this, with a front washer for extra pressure dispersion. Once inside the box, the spacer nut is placed, and tightened as tight as possible. do this with all four screws before going to the next step (only three brackets used, but there is still a fourth bold used). Next comes the speaker, aligned to all four bolts and lowered all the way to the spacer nuts, followed by a washer and a nut on each bolt, to hold the speaker in place nice and tightly.
Make sense? no?
Luckily I took a pic for you then, huh? :D
Once both speakers are mounted into the box, the next step is the wiring!!
Step 3: Wiring!
Next step is the Wiring...
These speakers are 16ohm. I know a bit about electronics, but speaker impedences is not my strong point. after checking up on the google-box, I discovered that iPods don't really care what impedence you use, as headphones come in all shapes and sizes. I did learn, however, that the headphone jack is outputting 5ohms, whilst the dock socket is for more high-impedence uses (hi-fi and docking purposes)
I don't have any idea about how to wire that 32 pin little devil of a plug, so sticking with the headphone plug for now, but could just as easily change it later on...
First, get the 3.5mm to 2xRCA cable, cut off the RCA plugs and strip & prep the wires. You should find a Red wire in one, and a White wire in the other, with both sides having a bare copper strand. The Red wire is the Right channel, the White is the Left channel, and the bare copper (on both sides) is the Common (or Ground) wire.
I have wired each speaker like an enlarged pair of headphones, with each speaker getting a signal wire (Red or White) and an Earth (bare copper wire). you can join the ground wires if you like, however it makes no difference, and using this RCA cable, it is easier to do it this way.
Wire each pair of wires to their own speaker. simple! With speakers, it really doesn't matter which way around the wires go, as long as each speaker gets a signal and an earth, it is all good. reversing the wires will do no harm to the speaker or the circuit on the iPod.
Step 4: Pumpin' Up The Volume!
Last step is simple...
Plug in an iPod or similar device and enjoy the sounds of your music anywhere you can carry it! The battery of the iPod will run about the same as it would with headphones, so you have potentially 20 hours of play before a recharge!
The cable I have used allows the iPod to be removed from the box and kept at a distance, or of course you could simply hit 'Shuffle' and put it all inside the box, keeping it random, but also keeping it wireless and portable!
Now, the other reason I put in spacer nuts on the speakers is this. This is a steel box, and if you are to have it outside in the Summer with an iPod in it, you run a risk of cooking the iPod. The spacer nuts allow some airflow around the speaker and through the grilles, allowing air to circulate, and lowering the temperature inside the box! Brilliant, huh?!
My next step is to add a plywood interior to the box, allowing it to be used to stash valuables in when I go for a swim at the beach, or perhaps simply to keep my lunch in there, without running the risk of it getting caught or snagged on the wires or speakers.
Another option is to add an amp into this, as the volume is only about speaking volume, however this would require either its own battery, or a corded power supply, and thus, going against the reason I built it in the first place...