Alright, this is a long post, but here are the drawings I made for an open back 1×12 guitar speaker cabinet after reading a lot online about how to make one.
I did not follow this plan exactly. These drawings assume I was going to use a dove tail joint for the four corners. Unfortunately my friend who had the tools didn’t have the right size jig for this project, so we ended up using a biscuit joint. This meant that the top and bottom boards were 16 inches across, but the left and right side boards were only 14.5 inches across. I used a standard 1 inch by 12 inch by 6 foot whitewood (hopefully pine) board that I got at my local hardware store. I went through everything they had and this one was the least warped or cupped. After finishing this box I agree with all those comments on the internet about the importance of finding a straight piece of wood. It is painful to make a square box with a bent, warped, or cupped piece of wood.
You’ll also notice that my drawings adjust for the real dimensions of the wood I was using. That 1x12x6 board is actually 3/4 inches thick and really about 11 1/4 inches wide. But it really was 6 feet long. Thanks to all the people on the internet who posted this warning!
I would also recommend going with a harder piece of pine because this whitewood stuff is pretty soft. My local hardware store had two kinds of boards. I didn’t go with the harder, straighter, and smaller grain pine that was three times more expensive because I was afraid I would screw this project up and have to start over. Might as well ruin cheap wood first, right?
I did get 7 ply, half inch birch for the baffle which I am happy with. I got some “hardwood” 3/4 inch square by 36 inch wood for the cleats and that seemed to work well. Finally, I got 1/4 inch birch ply for the back. I was concerned about weight, but in hindsight I think I would’ve saved some money and just used some leftover 1/2 inch birch ply for the back. Also, after putting the box together, it wasn’t a perfect square on the inside, so the baffle actually measures 14 7/8 by 14 1/2 inches instead of 14 1/2 by 14 1/2 inches.
Once I had all the wood, I measured everything and cut it. It is important to label things so the grain of the wood lines up and you keep putting things together in a way that the front remains the front and the back remains the back. My friend with the tools and workshop also used staples to hold everything together while the glue dried. After the glue dried we used a 1/2 inch router bit to round all the outside edges of the box. I used screws and glue to attach the cleats in place. I used screws with finishing washers (like cars use) for attaching the baffle and back pieces to the cleats. For any beginners out there (like myself), it is very important to predrill holes for the screws. Use a drill bit that is smaller than the screw diameter.
I haven’t made the grill cloth cover. I want to make it using cane, but we shall see.
IMO, the recipe for a good cab involves either 3/4″ solid pine (for a lightweight and resonant box) or 3/4″ birch ply (for a heavy and rugged cab that’s definitely less resonant). I prefer cabs that are uncovered, just stained and clear coated – again, to maximize wood resonance. The actual box dimensions aren’t that important, IMO – I prefer using 12″ wide (11-1/4″ actual) 3/4″ pine boards, and the finished cab width and height are at best arbitrary. A “floating” baffle is a good way to hang the speaker(s), using a pair of 3/4″ hardwood baffle cleats – I like stout 1/2″ birch ply baffles, some folks like more flexible 3/8″ ply baffles. I add a front 1/4″ baffle ply frame and a full grille (cloth is nice but wicker cane is wicked good!). You can seal off the cab, but I much prefer an airy open back, YMMV.
And his list of what he gets and does for a build:
cab box – clear (or knotted), low cupped, straight pine – 3/4″ x 11-1/4″
cab back panels -1/4″ birch or oak ply
baffle cleats – 3/4″ square red oak
rear panel cleats – 3/4″ square pine
speaker baffle – 1/2″ birch or oak ply, 7 or 5 ply
cleat screws – #8 1-1/4″ pan head + #10 washer
rear panel screws – #8 3/4″ pan head -or- recessed washer screws
speaker screws – 8/32 s/s machine screws 1-1/2″ + nuts
You’ll also need to consider …
– grille cloth or cane or metal
– matte back paint for the baffle front
– corners (maybe)
– covering and/or finish
– speaker(s), wiring, jack
And, what tools you have and how proficient you are with ’em.
My typical cab schedule is like this …
Label the boards for the dovetail process
Dovetail all four boards
Assemble the box – dot of yellow glue in each dovetail joint
Fill in an wood voids and cracks with wood paste
Sand dovetail EDGES with 80-100 grit belt sander
Roundover all external cab edges
Sand dovetails and sides with finishing sander, 120 & 220 grit
Measure/cut 1/4″ rear panels, 1/2″ speaker baffle (handle panel optional)
Stain and clear coat cab and panels
Install leather handle
Cut 1/4″ ply speaker baffle framing
Build baffle board: cut hole(s), glue framing, paint flat black
Clear coat the back of the baffle – only when covering w/cane
Layout and install four 8/32″ s/s speaker machine screws
Cover baffle with wicker cane or cloth
Soak cane grille for 45 minutes in hot water (not the cloth!)
Staple cane or cloth to baffle (allow to cane to dry and shrink)
Measure cleats: 3/4″ in for baffle, 1/2″ in for panels
Screw the pre-drilled 3/4″ oak baffle cleats (3 screws)
Drill jack hole in upper panel – 3/8″ bit
Assemble jack into 1/4″ rear panel, solder leads
Screw the pre-drilled 3/4″ pine back panel cleats
Install rubber feet
Screw speaker to the four baffle screws
Screw baffle to cleats – #8 1-1/4″ screws + #10 washer
Solder speaker leads & screw in top panel
I didn’t sand or fill anything before I put it together (See pics here). I had limited time with my friend’s tools and shop. I’ll finish (as in filling and sanding) on my own time in my own garage. I will say now that I’ve got it all together, it will be hard to take it apart and not have it while I finish it!