Make a Passive Smartphone Speaker
Amp up your music listening experience by making a sleek speaker for your smartphone.
I love bending wood. In fact, veneering and bending wood was the favourite part of my formal education.
Bending wood seems magical, but there are several ways to make this happen, and we’ll use one of these ways to create a smart-looking smartphone speaker.
Built-in speakers have come a long way since Apple introduced the iPhone. We’re going to enhance this sound in a stylish manner by making a passive speaker. Sure, you could order a Bluetooth speaker, but aren’t we woodworkers? Let’s make our own.
A Curved Form
The exact radius for the form isn’t important, so Der-Garabedian uses a thin piece of material to give him an even curve to trace.
Flush the Joints
Once the first piece is shaped and smoothed, Der-Garabedian adds a layer to either face of the initial piece and flush trims those pieces on his router table.
Der-Garabedian resaws thicker stock to obtain six laminations 1/8" thick. Notice the cabinetmaker’s triangle on the upper edge of the stock so he can glue the layers up how they were cut from the board, ensuring even grain and colour.
Holes to accept the clamp jaws can be added to the form. This allows the user to add clamping pressure perpendicular to the joint over the entire curve.
Used to keep track of multiple parts, a cabinetmaker’s triangle is helpful in many situations. These parts are cut from one piece of wood and will be glued up as they were cut from the board.
Rip It to Width
A bandsaw will give you the width you’re after.
Time for Glue
Apply glue to the laminations and get them onto the curved form. Thankfully, with only three laminations there’s no need to rush.
Because the grain on the board Der-Garabedian started with ran on a slight angle to its edge, once the board was resawn in half and bookmatched, a slight fan pattern is visible on the top and bottom panels.
One Straight Edge
A jointer will make quick work of the curved laminations, giving you one straight edge to work with.
Der-Garabedian uses his table saw crosscut sled to obtain consistent results when crosscutting the laminations.
Not Too Cramped
Though you don’t want the inside of the speaker cavernous, you don’t want it too tight, either. A bit of room at the end of the speaker for your phone is all you need.
Der-Garabedian sets the ends of the sides at a right angle, then measures how wide the top and bottom panels need to be.
Taper the Sides
A template makes it easy to mark the two sides evenly.
White glue works well on wood, but it won’t hold the brass pins well. Der-Garabedian mixes up some two-part epoxy to secure the pins once the joint is together.
Block Plane to the Rescue
A block plane will smooth out any unevenness in the joints and allow the top and bottom panels to sit flush on the sides.
Strong Visual Effect
Wanting to make the most of the fan pattern on the top and bottom panels, Der-Garabedian does everything he can to ensure the top and bottom are centered.
With the top and bottom located on the sides with brass pins, Der-Garabedian draws an arc on the top and bottom panels.
Der-Garabedian routs the phone groove on his router table, but an alternative method would be to clamp a straightedge on the top panel and use a plunge router to plow the groove.
Small blocks are machined and attached at either side of where the phone will sit, immediately below the groove. Larger blocks may stand the test of time better if kids are going to be using this speaker.
Ready for Assembly
With the parts machined, it’s time to bring them all together. Der-Garabedian chose to apply a finish to the parts first, as getting inside the assembled speaker might be a bit tight.
Der-Garabedian applies a few coats of finish to the inside and outside of the parts. Blue tape protects the glue joints from getting any finish on them.
So glue doesn’t squeeze out everywhere, apply it sparingly and with a small brush.
Small Phone Supports
CA adhesive does a great job at fixing the small phone supports to the sides.
Flush the Pins
Once the epoxy has cured, use a file to smooth the brass pins.
Flush the Top and Bottom
With the speaker glued up, use a flush trim router bit to even out the joints at both sides.
Bring It All Together
One clamp will provide enough force to bring the speaker, leg and foot together for good.
High school horn
A few years back, I made a crude version to test how well this would work. To my surprise, it worked quite well. But the time has come to up the ante and make one that I can be proud to put on a shelf and use to listen to music, podcasts or audiobooks with a bit more oomph. When I started thinking about Version 2.0, thoughts of high school and those bellowing announcements from loudspeakers on high posts came to mind.
As mentioned before, there are several ways to bend wood. You could cut a curve out of solid wood, but this usually leads to a lot of waste. Steam bending is another option, but I find this has as many cons as it does pros. One of my favourite ways is to make a form and use a flexible plywood like wiggle wood and veneer to create a shape. In the end I settled for bent lamination as I had just the right piece of walnut.
It’s all in the form
Before making the form, I made a drawing on a piece of graph paper to give me a close approximation of both the shape and size of the speaker. Once I was happy with the sketch, I cut up five pieces of MDF. With a few modifications this form can be used in a vacuum bag to bend wood.
Start off by driving a pair of screws along the curve’s path partway into one of the MDF pieces. I used a cut-off piece of 1/8″ thick MDF to create my curve between the two screws. Most any clear piece of wood around the same thickness will do the trick, as well as store-bought options like a French curve. Play with the shape until you’re happy and then pencil it in. Next, cut this on a bandsaw and refine it with sanding. Take your time with this step to make a smooth curve because this will become the pattern.
It’s simple to create identical pieces by using a combination of a bandsaw and router fitted with a flush trim bit. First, create a 90° corner jig using a pair of MDF pieces, glue and screws. Seat one of the blank MDF pieces in the jig, then place the curved template on top. Using a countersink and three #8 × 1″ screws, attach the two pieces together. Keep the screws close to the outer edges, as you’ll need to drill holes for clamps in the middle. Head over to the bandsaw and cut the curve, leaving approximately 1/8″ of waste. Take your time and don’t cut into the template.
At the router table, place a flush trim bit with a bearing on its tip in the router and adjust the height so the bearing rides on the template. Route the assembly to give yourself two perfectly matched pieces. Head back to your bench and place a blank into the 90° jig. Next, put three or four drops of medium Instant Bond CA adhesive on the assembly and spray accelerant on the blank. Lay the assembly on top of the blank and let it set for a few seconds. Turn the new assembly over and drive in three screws, once more keeping them close to the edges.
A few more touches
Keep repeating the steps with each blank and in short order you’ll have a form that is 3-3/4″ wide. Sand any sharp edges and apply packing tape to the form so your lamination doesn’t stick to it. I drilled four 1-1/2″ holes completely through the form to accommodate the pads on my F-clamps. Adjust the position and hole size to work with the clamps you have in your shop. To find the positions of the holes, place the clamps perpendicular to the curve. Remember to avoid the screws holding the form together. One other addition is to place two small blocks on one side of the form to help align the laminations during the gluing process. These blocks are roughly 3/4″ thick by 1″ wide by 4″ long. Cover these with packing tape before screwing them to the form between the clamps. Make sure they are at least 1″ above the curved surface as four pieces of 1/8″ hardboard will be used as clamping cauls.
Slice and dice
I wanted to make the curved sides of the speaker 3/8″ thick to make it light yet easy to join to the top and bottom. This will require three 1/8″ thick pieces for each side. When laminating wood, the thinner the individual slices, the easier they are to bend. While our bend is not too radical, it is made easier with thinner slices. Thinner slices mean less spring-back when the lamination comes off the form.
Start off by milling a piece of walnut or wood of your choice 1-1/2″ thick by 3-1/2″ wide and 15″ long. Longer and wider allows some wiggle room to clean up the laminations after the bend is formed. It also lets you select the part of the curve that suits you best. Set the bandsaw up to re-saw 3/16″ thick laminations. Depending on how well your bandsaw is tuned up, you might need to take the last lamination from another section of the plank. Whenever I make laminations, I mark up one edge with a woodworker’s triangle to keep the laminations in the same order in which they came off the plank. By gluing up the laminations in this same order and using white glue, which dries translucent, it makes the lamination look as if it grew in this particular shape. Even though the edges of this project will be covered, it’s a good practice to follow.
The process is to re-saw a piece and set it aside. Next, run the rough side of the remaining plank through the thickness planer and re-saw once more. Keep repeating the process until you end up with six pieces. Now run these pieces through a thickness planer until they’re 1/8″ thick.
Around the bend
Almost every time I use clamps, I’m also using cauls. In this case, to accommodate the bend, I’ll use four pieces of 1/8″ thick hardboard to help spread clamping pressure and mitigate against flat spots on the lamination. Cover one of the four cauls with packing tape so it doesn’t become a permanent part of the lamination. Complete a dry run of the clamping process to see if there are any spots along the bend that need more pressure in the way of more clamps. If you need to add another clamp, offset the hole in the form a little lower than the others. In my case, I found that the ends could use some help. For the top of the curve, a clamp and caul worked great. For the bottom I needed to add a 45° block allowing pressure to be applied inline without slipping. Add this block using glue, and either brads or pins.
Cover your bench with newsprint and gather your laminations, glue and clamps. Spread glue on the joint faces of the three laminations and stack them on the form. Add the cauls, making sure the taped one is facing the lamination, and start clamping. Check to make sure the pieces are lining up and, if necessary, tap them back towards the side blocks. While there is some wiggle room, it’s better to take care of misalignment before the glue sets.
I like to leave bent laminations pressing for at least 24 hours. When you remove the clamps, chances are you’ll see some spring-back, especially if you used a PVA glue such as white glue. PVA glues don’t dry rigid and have what is called cold creep. On our curve this means there will be a spring-back of approximately 1/8″ from each end. With this in mind, it’s good practice to make the curved parts of a project first and match the remaining parts to it. Repeat the steps above for the second set of laminations.
Top and bottom
To make the top and bottom of the speaker I re-sawed a part of the plank that had the grain running off at a slight angle to the edge. Bookmatching the two halves created a fan pattern that complements the shape of the speaker. I started with a piece long enough to get both the top and bottom, as well as trim off any snipe. However, a few passes with a hand plane could easily remove it just as well. Having the top and bottom slightly thicker helps with the joinery and also better accommodates the base. With this in mind, mill the pieces to 7/16″ thick. After jointing and bookmatching, I ended up with a width of 11-1/2″ and a length of 24″.
Squared and tapered
At this stage, it’s time to clean up the bent laminations before tapering their widths. Do several test fittings to see the overall shape of the speaker. Position your phone at the rear and get a rough shape and length of the speaker. Mark this on one curve and trim to your marks on both ends. Stabilize the lamination on a crosscut sled by using clamps and a wedge to support the curve. To transfer the length to the other curve, stand it on top of the other, as opposed to placing them side by side, and make your marks. Cut this curve as before.
Head back to the bench and place your phone once more between the curves to see if you’re happy with the shape. Trim some more if you’d like. I wanted to flare the curve out a bit more and this was easily accomplished by cutting angles on the ends of the rear block. Be sure to stay within the size limits of the panel for the top and bottom. I used a sliding bevel and ended up happy with a 5° angle. Mill up the rear block and cut this angle on both ends using a table saw or bandsaw.
To make the template for the taper, I used some wiggle wood the same length as the inside of my curved pieces. The taper that seemed pleasing was a 2″ width at the back to 3″ up front. Cut this on the bandsaw and refine it with a jack or block plane. A bird’s mouth holding jig like the one in the June/July 2021 issue does an excellent job of holding the curves while you plane them. Keep comparing the two curves to each other, making them as close to identical as possible because they will eventually sit in the speaker. However, being off a little won’t really hurt the sound.
Once you’re happy with the curves, glue the rear block in place. Sit the block on your bench and clamp the curves to it. Transfer the width of the curve to the block. Leave this width to the larger portion of the curve instead of trying to make a compound cut. I find it much easier to flush it up after the glue has cured with a block plane rather than try to hit the angles at the table saw.
I had a few 1/8″ brass rods left over from a previous project and since brass and walnut look good together I thought I could not only add some support to the joints but some pizzazz, too. Lay out and drill 1/8″ holes 3/4″ deep, centered on the rear block and equidistant from the centerline of the sides. Using a small hack saw, cut the brass rod approximately 7/8″ long. Cut 16 pieces in total.
Use regular white glue for the wood-to-wood contact and mix up a small batch of epoxy for the brass. I had five-minute epoxy on hand, but longer-setting epoxy will work perfectly well. Use cauls and clamps to complete the assembly.
Flush, flush, flush
Once the assembly has fully cured, clamp it in your vise and file the brass rods flush. I started off with a rougher, 2nd cut file and switched to a finer file as I got close to the surface. There will be some final sanding later so don’t worry too much about a few errant file marks.
Use a block plane to flush the rear block to match the taper on the side pieces. The back will be somewhat uneven, but this will be smoothed out later.
Blue tape to the rescue
Lay down some blue tape on the center of the panel for the top and bottom. Use blue tape to also define the center of the rear and front of the assembly you have so far. Mark these clearly with either a sharp pencil or fine black marker.
Set the assembly on top of the panel to determine its position. This will be done several times to determine the length of the top and bottom as well as to transfer the shape of the sides. I thought it would be visually pleasing to add a bit of a bow to the front edges of the top and bottom so I cut these approximately 1″ longer. Cut the top and bottom to length, then place the assembly back on top of each piece and pencil in a curve at the front as was done before, using a thin piece of wood and clamps to hold it in place. Using an offset wheel gauge or a small washer, trace the outside of the sides onto the top and bottom. Cut this out on a bandsaw and only refine the shape of the front by sanding. In fact, it’s easier to tape the top and bottom together and sand their fronts as one piece. Leave the sides rough and proud for now. They’ll be flushed in much the same manner as when the form was made.
Pins, but not needles
With the top and bottom shaped closer to final size, it’s possible to more accurately locate the brass pins. Mark the top and bottom pieces to make sure they will always be properly oriented. The brass pins are placed 1″ in from the front and back of the speaker. Another pin will be located in between these two on both edges. A cloth measuring tape made for tailors is a perfect way to follow an odd shape such as this one. Using a cordless drill fitted with a 1/8″ brad point drill bit, drill these holes, making sure to hit the centre of the sides. I found the centre by measuring the overhang and adding 3/16″. Mark the spot using an awl and repeat for the rest, as well as for the six on the bottom.
Since the rear block is 1-1/4″ thick I started the slot for my phone 1-1/2″ from the back. My mortise ended up being 9/16″ wide as I wanted to use the speaker while keeping the protective case on my iPhone. Centre this mortise on the top according to the size of your phone with some clearance to let it slip in and out. While routing this groove make sure the flat, rear edge of the workpiece stays in contact with the router table fence. It’s easy for it to shift, causing the groove to be unsightly or something worse. You could also rout this groove before or after using a straightedge clamped to the workpiece while moving the plunge router.
Some additional parts
To make sure the phone doesn’t drop through and come to rest on the bottom, make supports that are small enough to hold the corners of the phone yet not block the speaker. Once more, this is dependent on the make and model of your phone. Supports can easily be made by taking a small, square piece of wood 1/2″ thick and 1-1/2″ square. Drill a 1″ hole through the center and cut it into four pieces. You’ll need two pieces which will eventually be glued to the underside of the top. With the top dry-fit into place, adjust the supports as necessary. If you know you’re rougher with things, make these supports a bit larger. You don’t want them to break down later.
I’m not a sound engineer, but I imagine that sound waves bounce similarly to billiard balls. With the phone sitting perpendicular in the top’s slot, the speaker will bounce the sound waves straight into the bottom. In practical use, this worked well, but while experimenting I found that placing a piece of walnut cut at 45° against the rear block improved the output. With the curves and tapers of the speaker, fit this bounce block as close as you can. It doesn’t need to be a perfect fit for it to work.
The base is made from two pieces of walnut. The foot has a similar shape to the speaker, but with a straight taper from front to back rather than curved. The top of the leg is angled backwards at approximately 7° to project the sound into the air, should the speaker be sitting on a desk or shelf. Centre the leg on the foot with a pair of 1/4″ dowels 1″ in from each end. Drill for 1/4″ dowels at the top of the leg with the same positioning, keeping in mind this surface is angled. Add a clamp and clean up as needed.
Start the finish
While I could fit my hands into the assembled speaker, I thought it wise to add the finish before final assembly. I opted for Osmo Polyx-Oil, but any finish will do. Sand all parts inside and out. Mask off any areas that will get glued. For the top and bottom to the sides, I placed masking tape along the inside edges of the top. I dry assembled the top to the sides with a pair of pins and then, using a scalpel style of knife, I carefully cut away the exposed tape. Do the same for the bottom and don’t forget to tape the sides. I applied two coats of finish to the inside and one to the outside, knowing that touchups would be needed along with an outer second coat.
Once the finish has cured, dry assemble the top to the sides, and using both regular woodworking glue and Instant Bond CA adhesive, glue the phone supports to the inside of the top. Leave a paper-thickness amount of space between the back of the supports and the sides to prevent hindering assembly of the speaker. Later, epoxy will be added to fully lock these in place.
Next, glue the bottom to the sides using glue on the contact points and epoxy in the holes for the brass pins. After dry fitting two pins and locating the bottom to the sides, apply epoxy to the remaining four holes for the pins. Drive these in and then remove the first two. Add epoxy and drive the last two pins into place. Add clamps and let the assembly cure. After removing the clamps, glue the 45° bounce block to the bottom.
To find the mounting point on the speaker’s bottom for the base, place a piece of folded sandpaper on the top of the leg and place the speaker on top. Place your phone in its slot and move the whole assembly back and forth until you find a good position that’s balanced. Center this left to right and if you bookmatched as I did you will already have a center line. Drill the two 1/4″ holes in the bottom about 3/8″ deep.
Last little touches
Glue the top to the assembly using the same steps as you used for the bottom. Don’t forget to add a small amount of epoxy to the phone supports where they face the sides.
Once the assembly is out of the clamps, use files as you did before to flush the brass pins to their respective surfaces. Next, head back to the router table with the flush trim bit and flush the top and bottom to the sides. Since the top and bottom extend past the front of the sides, pay attention to where you start and stop the cuts. Use sandpaper to round over those points and flush them to the sides. Use a block plane to flush the back of the speaker. Glue the base to the speaker using cauls and a deep-reaching clamp to apply pressure while it cures. Clean up any scratches and apply the final coat of finish followed by a fine furniture wax.
I’m looking forward to listening to my new audiobook while working around the house or the shop. You can add a charger cable to the speaker by drilling a hole in the bottom and feeding the cable through. You can also add a support for your phone behind it, should you feel it is not held securely.
If you’ve never tried bent lamination, this is a great project to get you started. If you have, try your hand bending with a vacuum bag, some wiggle wood and veneer. I’ve already started to make another smartphone speaker as I’ve caught my girlfriend eyeing this one.