Introduction: Scrap Plywood to Custom Speaker Project
For this project I set out to build myself a completely custom speaker that would sound great and look clean and simple. I built everything from the ground up myself, except for the speaker drivers. However I built everything else; the circuit board, the amplifier circuit, and the housing. I even tailored the speaker circuits inductors and capacitors to make the high and low pass circuits that produced the custom sound I wanted. The speaker can reach up to 100db with almost no distortion at all and is a sealed enclosure so it produces very accurate sound. Also the thick and durable plywood produces a stiff and distortion-free sound while still looking stylish.
Step 1: Materials and Tools
- Alligator clips
- Various Electronics Components ( refer to the schematic )
- Full Range Speakers (2) Full Range Speakers ( I used these )
- Tweeters (2)
- Speaker Wire
- Speaker Gaskets
- Assorted Nuts and Bolts and screws ( to attach the speakers )
- Wood Glue
- Hot Glue
- Heat shrink tubing
- Paste Wax
- Paper Towels
- Scroll Saw
- Band Saw
- Belt Sander
- Drill Press and Assorted Drill Bits
- Soldering Iron and Desoldering Braid
- Combo Square
- Assorted Chisels
- Disc Sander
- Drum Sander
- Spindle Sander
Step 2: Cutting Housing Segments
The box consisted of 9 pieces of 3/4 in. plywood laminated together, 7 of which were hollowed into 3 compartments. Each piece is 6x15 in. and they have rounded edges. To do this cut out all 9 of your pieces on a table saw or panel saw. Get them all identical before you round out each pieces corners. To round the edges use a disc sander and steadily rock the corner back and forth. Do this for all nine pieces, but then set aside two of them to make the top and bottom of the speaker.
Now with each piece draw out the three compartments for each speaker. To do this draw a half inch border around one of the pieces and then draw out from the 1/2" border two 5x4.75 in compartments on either side and give them 1/2in walls on the inside too. If you layed out everything correctly you should have two 5x4.75 in compartments on the sides and a smaller one in the middle(refer to the drawing for help with specs). Each should have 1/2" walls. Now drill holes in each corner of the piece you just layed out. Then put your piece into the scroll saw and cut out each compartment..Then go over to the spindle sander and sand the inside of each compartment untill the walls are nice and smooth This helps to keep everything consistent and easier when it comes to sanding. Now you have a piece to trace all your other pieces to. Once you cut them all out they should line up nicely, but if they don't you can always sand it after you glue them
NOTE: Take your time cutting in this stage, the more accurate you cut the less time you will spend sanding.
Step 3: Gluing and Sanding
Once you have all 9 pieces cut, it's time to get gluing. You will only glue 8 of the 9 pieces together because you will want to take off the top to be able to insert the speakers and all the electrical components. So glue the bottom to the the 7 hollowed out pieces and use the ninth top piece to clamp to and distribute even pressure over all edges. Use glue sparingly because you don't want it dripping inside or else it will be very difficult to sand out.
Don't expect all your pieces to line up because they won't and that is what the belt sander is for. While sanding use a relatively aggressive grit like 60 or 80 grit. This is because if you use a high grit it will clog up much easier and then burn the wood and overwork the motor. Not only that you will spend way too much time sanding and end up frustrated. So use the belt sander and sand everything even and all the glue until it is even and free of divits. Also sand the bottom piece and the top piece. However do this very sparingly because it is plywood and you don't want to sand it the next layer by accident.
Step 4: Drilling Holes for Speakers, Lid Assembly, and Waxing
Laying out the holes for the speakers is pretty simple. Use your combination square to draw lines where your walls are and then draw diagonals from the corners and where they intersect is where you need to drill. Then for the tweeters do the same except drill two holes centered with the same method as before. Once you lay out the holes your gonna need to play around with drill bit size. This took me a bunch of tries, but you want to get the fit good so the speakers make a good seal. A good seal will result in more accurate sound. Once you find the correct bits put them into your drill press. Before you drill you must slow the speed of the motor because it is such a big bit. If you don't it will create too much friction and just burn your wood instead of actually cutting it. So go and drill, but slow and carefully to reduce tearout on the housing. Once finished drilling clean up the holes and pull of any splinters. Then insert the speakers to make sure they fit well. But be careful and don't drop your speakers like I did.
The lid is attatched with four screws in each corner. To do this make sure you drill pilot holes because the plywood can easily split. Before you screw it on make sure it is sanded to perfectly match and appears to be glued on without gaps.
Before you start waxing make sure your housing is perfectly smooth and how you want it to look. Now you don't have to use wax as your finish, but I chose to use it for its ease of use and beautiful sheen. Using paper towels rub in a thick coat of wax to the entire outside of the speaker housing. Then give it about 10 minutes for it to sit while the wax soaks into the grain of the wood. Then with a handful of clean paper towels wipe off all of the excess wax. Next you will want to use more clean paper towels to buff it to a nice smooth feeling surface. If it still feels tacky that means you must keep buffing. You can do up to four coats of wax, but it is totally personal preference. Play around with it on some scrap wood and see what you like.
Step 5: Putting in Holes for Audio Jack, On/off Button, and Power Jack
This step was a bit tricky for me and my speaker. Also your ways of inserting the buttons will vary especially if you have different buttons, but this is how I did mine. Since the plywood walls are relatively thick it is hard to use the nuts included with the sockets. So I had to come up with another method for each one. So for the audio jack you must carefully chisel out a notch for it to sit. Make sure to make it big enough to fit the pins and the wires soldered to it. Make it big enough so they don't touch the wires, if they do it will really screw up your sound. Then hot glue it in place and also use hot glue to fill up the space where the wires are and to insulate them.
Then for the DC power jack use a drill bit size so that it will fit in snugly with the nut on the threads. Play around with drill bit size because not every power jack is the same. Then use a small amount of hot glue in between the body and the nut and slide it in. Take care to not get glue in the power jack or else it will not be usable.
The on/off button hole will vary based on what type of button you use. But for mine I drilled a hole so it would snugly fit in place. Then I countersunk it with the largest countersink bit I had and then used a chisel from there to give you access to the on/off toggle. From there I hot glued it from the back to secure it into the housing.
Step 6: Building the Amplifier
For the amplifier this will definitely take a lot of time as it is not an easy circuit to build, but will be very rewarding in the end. Not only that, but you can customize the high pass and low pass filters on the speakers to achieve the sound you want. Also for this circuit I used a custom printed board made by a friend of mine, but this project is still do-able even without this exact board. To do this first breadboard the entire circuit out and make sure it works also make sure your bench-top power supply is set to 12v. Use alligator clips to attach the speakers and play some music to test it out. If you can't get it to work than use some troubleshooting tips I added in the photos. Those should cover some of the most made mistakes, however if it doesn't, than pull out a multimeter and start checking your circuit. Once it is working you can now play around with different high pass filters for the tweeters. This is totally personal preference, there is no better sounding option, just pick one you like. Make sure every thing is just how you want it before you transfer everything to circuit board. While soldering be very careful because a mistake could set you back a lot of time and make you very frustrated. If it doesn't work when you finish, again go through the troubleshooting tips I wrote up(in photo section). At this point you are ready to start assembling your final product.
Step 7: Installing Speakers
Installing the speakers was a surprisingly time consuming part of the process for me. The reason it is so difficult is when trying the thread on the nuts in a tight space, the nuts will get sucked into the speaker's magnet. You don't want to leave them there because the could interfere with the speaker or rattle around while your enjoying some music. So the first thing to do is set the speakers into the housing the way you would like them to sit when you are done. Take your drill and drill bit and with one hand hold the speaker still in the hole and with the other drill out the holes for the bolts. Do this for all of your speakers and then lightly clean up the holes with some 220grit sandpaper. Now before you install your speakers be sure to solder your speaker wire to them first and cut the speaker wire a bit longer than you will think you need(It sucks when you have to take everything out because you cut your wire a 1/2" short). Put on your speaker gaskets for the full-range speakers and make sure you line up the holes on the gasket. If you forgot to put the gasket on before you squeezed the speaker in like I did, than just cut open the gasket and slip it on from the side. The nuts and bolts only have to be hand tightened, mainly because that is the best you will be able to do. It is such a tight space that all I could fit was a ratchet fitting in my hand, however that gets it plenty tight and I haven't had any issues with it yet. At this point you will need to chisel out a groove in the speaker walls for the speaker wire to fit. The amp will sit in the middle compartment with the tweeters and the speaker wires will need to be attached to the terminals there. So carefully chisel out some grooves for each speaker wire to fit under the lid. Use a sharp chisel and be sure to go against the grain so you are actually cutting the wood and not just splitting/splintering it.
Step 8: Installing Amplifier and Finishing
Now you are almost done so grab the amplifier circuit you just built and hook up all the speaker wires to their appropriate terminals and make sure all the wires are tucked away and neat. Then put a bit of hot glue on the bottom of the circuit board and glue it to the bottom. However don't use too much glue or else you could overheat and break some of the more sensitive components. Next grab your lid and make sure it fits over a the speaker wires and audio jack. If so, you can go ahead and screw it on using the holes you made before. You are now done so it's time to test it out. Plug in your audio jack and power jack, switch it on and play some music !! I found this speaker to better than most retail ones you can buy. It has reached up to almost 100db, it has incredibly good bass response and the tweeters balance that out to create very accurate sound. I now use this speaker over any other ones in my house. Overall I was extremely pleased with the outcome of this project and I hope yours comes out even better !!