- 1-2 8 ohm speakers
- an enclosure (cardboard box, tea tin, coffee can, etc.)
- insulation (cotton, an old shirt, the hair you get from your pet when using the Furminator.)
- glue ( any will do, but… I cannot recommend a hot glue gun enough. see below)
- alligator clips (deluxe version) or just some metal bit that will conduct the signal.
- soldering iron (and solder)
- X-acto knife or other cutting tool (depends on the material of your enclosure.)
- wire cutters/stripper
- helping hands
- hot glue gun (and glue)
As the asterisks in the title imply, and as you know from life, nothing is free. If you don’t have the parts, you will have to acquire them. There are ways to get the parts necessary for free, but probably not the tools. If you don’t have a soldering iron and a wire cutter / wire stripper, borrow them from a friend. Better, if you plan on doing more DIY electronics, pick them up for yourself. For the speakers and wire, just keep an eye on your apartment building’s dumpster, the alley next to your workplace, or your workplace trash. I guarantee you will find 5-10 discarded electronics that have what you need within a few days. You can ask around the office too — chances are someone has something laying around they don’t want and have been meaning to throw away but haven’t yet. If it makes noise, chances are there’s an 8 ohm speaker in it. Their trash is your desktop test speaker.
For testing audio circuits, you do not need a high-def sound system. In fact, using one is probably a bad idea being that you really have no idea what is going to come out of some circuits and the results can be… unpleasant. You can use the little speakers you find just as they are alligator-clipped into the circuit too. The problem with this is, with no resonating body, these little speakers have very low volume and sound tinny and thin and do not give you an accurate idea of bandwidth of your circuit. Making an enclosure, however, is pretty easy.
Pick and Prepare Your Enclosure
I chose a thick cardboard box I had on my workbench. I have too many of them and always say I’m going to make something with them. I finally did. Cardboard is a good choice as long as it’s reasonably thick because it’s an easy-to-cut and relatively forgiving material. Also if you screw up, you won’t feel too bad — it’s only cardboard. Be sure to make the enclosure a proportionate size to your speakers. A considerable size mismatch will make it less effective.
Put the speaker upside down on the inside of the enclosure and draw around it with a pencil. This is your guide line. Check out the underside of your speaker. You will see a lip around the edge. Measure to see how far this lip is from the edge and make that your cutting line. For example, I drew my guide circle and then cut 1/8 inch in from that circle to match the lip on my speaker. It is always better to err on the small side. You can always cut more — Uncutting is not an option.
Grab your X-acto and, slowly, cut around the inside of your marking. Take your time, you don’t want your project delayed by a trip to the bathroom for band-aids. Stick the speaker in the hole and see how it fits. The rounder your cut, the better it will fit. If necessary, make adjustments. If you cut the hole too big, grab your glue and some cardboard from the initial cut. First glue a brace piece on the inside of the box that covers the gap. Then cut that to the right shape. Cut another piece of cardboard to match the shape of the difference between the box and the glued-on piece, and fill the gap. Now the front should be even.
Next, cut holes for your speaker wire connectors. These are what you will clip your circuit audio outputs onto. I used two speakers so I cut four small holes and used alligator clips I had from a previous project. I put my clips on the back of my speaker, but it doesn’t really matter where they go. Make the holes smaller than the contacts for extra stability.
Glue Glue Glue / Solder Solder Solder
Depending on the shape and the material of your enclosure, you will either want to solder first and then install and glue or glue the speakers and contacts in and then solder the wires up. Because my box has an easy swing-open cover, and it is relatively shallow, I glued my speakers and clips in first, and then soldered the wires in. Think about this step before you start – the minute of consideration can save you some annoyance later.
For glue, I used a hot glue gun. I can’t recommend buying one strongly enough. They are inexpensive, the glue is stretchy and durable, and it goes one easily and dries in seconds. You will end up using it way more than you think if only because it is fun as hell.
When you apply the glue don’t be stingy, but don’t be careless. What you want is a complete seal around the edge of the speaker’s metal frame and the enclosure without getting glue on the speaker membrane itself.
- Apply the glue to the very edge of the outside of your box.
- Put the speaker in and let it sit for a minute
- Flip the box over and, on the inside, look for gaps. If there are any, fill ‘em with glue.
For the contacts or clips, just dab glue around inside and out. Wait a couple minutes and jiggle them around to see they are in place and stable.
If you soldered first, you are done. Congrats! If not, solder the speaker wire from the speakers to the contacts. Be sure you mark + and – and connect accordingly. I marked this on the outside of my box. Use enough wire so that there is plenty of slack.
The last thing you need to do is stuff the enclosure with something. Grab a bunch of cotton balls, an old t-shirt, foam, whatever, and gently fill the enclosure. You need enough wire so that the insulation doesn’t pull the wire out of the speaker.
Close it up and Enjoy
That’s it. Super easy. Now plug it into a circuit and see how it sounds. Terrible? Try a different speaker, or a different box. Try different insulation. Remember, you made this thing from trash using a glue gun – it’s not going to sound like angels singing Handel, and it’s not going to last forever. What it is going to do is sit on your desk providing you with a quick way to test your audio circuits. And, hopefully, it didn’t cost you anything!
Have ideas for where to quickly/cheaply get speakers or other components? Have you made your own test speakers? Post about it in the comments section!