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These stylish amplifiers not only boost volume but can also improve the sound quality of your phone’s built-in speaker.

Project #2412 • Skill Level: BeginnerTime: 2 DaysCost: $5

Plastic smartphone amplifiers can be had for about $15 a piece, but expect to fork out $100 or even more for a fancy handcrafted wooden one. They give a louder and richer sound than the phones by themselves. In a nutshell, they are just a box with a front opening and with a slot on the top to accept the phone. I made mine out of poplar and plywood scraps. In this article, I will show you a well-thought-out process that guides you through the making of a large batch of amplifiers in as few as two shop days. With literally everyone—young and old—owning a cell phone nowadays, these amplifiers could well be one of the most popular gifts you ever make.

The speaker can also do double-duty as a coaster.

Cutlist and Diagrams

Create the Design

Phone amplifiers can be made in all kinds of shapes and sizes, but a trumpet-shaped cavity will give the best amplifying results. I prefer a more compact design and the whole box measures 13/4 x 41/2 x 5. For a more stylish look, I designed the box to be in a speaker shape instead of a square or rectangle, as commonly seen. While primarily an amplifier, I also use it as a cup stand in the shop. You can add any other desirable features to your design, such as making it a charging station as well.

Given the angled shape of the amplifier, it would be quite a challenge to build it with any traditional joinery such as a dovetail or butt joint. My solution was simple and easy to execute: first, I laminated three pieces to form a rectangular box with a hollow chamfer. Then, I cut the box into its final shape.

Drill the Top and Middle Pieces

Start with the rectangular pieces for the top and middle and mark the two center points for the slot holes on the top piece. To drill those holes without resetting the fence and stop block, use what I call a “stop block and spacer” setup, as described below:

1. Install a 5/8 diameter drill bit in the drill press.

2. Use the left center point on the top piece to set up the fence and stop block.

Align the left center point with the drill bit. Lock the stop block in place.

3. Stack the top and middle against the stop block and drill the left slot hole.

Drill the top and middle pieces together as a stack placed against the stop block.

4. Reposition the top piece so the right center point aligns with the drill bit.

Move the work to align the right center point with the drill bit.

5. Measure the spacing between the top piece and stop block.

Measure the spacing between the stop block and the work.

6. Cut a spacer to the exact measurement of the spacing and put it aside.

7. Place the spacer against the stop block and the stack against the spacer.

8. Drill the right slot hole through the stack.

Place the stack against the spacer and stop block. Drill the right hole.

Cut Out the Slot

With the holes drilled, mark out the slot and cut it out on the scrollsaw. If you plan to cut out the slot with a jigsaw, put masking tape on the lines to prevent tear-out.

Using a scrollsaw will give cleaner and straighter cuts than a jigsaw.

Rout the Slot

If the slot you cut is in good shape, you can sand its edges smooth and leave it at that. However, I prefer a more refined look and chose to chamfer the slot with a router bit on the router table. The routing steps are as follows:

1. Install a fence and position it so that the router bit chamfers the outer edge of the slot.

Mark the start and end points on the fence to prevent routing beyond the slot ends.

2. Clamp the top piece upside down in a handscrew and feed the work from left to right against the spinning direction of the bit.

Rout with the work going against rotation of the router bit.

3. Reposition the fence to rout the inner edge, feeding the piece from right to left.

Mark out the cavity on the middle pieces.

Cut Out the Middle Piece

To turn the middle piece into an amplifying chamber, draw lines on the piece to mark out the trumpet cut-out. Use the bandsaw to cut out the core in a stack of two or three pieces together.

Tape two or three middle pieces together and saw out the cavities on the bandsaw.

Laminate & Shape Box

Remove any rough edges on the slot and cutout. Glue up the three pieces to form the open-ended box. After the glue is cured, lay out the angled lines on the top piece, and set up your miter saw to cut them. With the use of a stop block, cut the first angled side of all the boxes. Reset the miter saw blade and stop block for the opposite angled side and make the angled cuts to produce the final shape of a speaker. Lastly, round all the corners on the oscillating drum sander.

Remove the saw marks on the cutouts by hand or on a belt and disc sander.

The rasp is the tool of choice for removing burn marks.

Glue and clamp all the laminated boxes in one go.

Position a stop block to cut one side of the amplifier to an angle.

Pivot the blade to the other side to the desired angle and set up a stop block for the second cuts.

Round the corners for a nicer look and feel.

Add a Finishing Touch

Sign and date each amplifier and attach self-adhesive pads on the front corners for a slight tilt at the front. Decorate the piece as you wish (my wife, Lorraine, made the suggestion of using a patriotic theme in the painting) before applying a few coats of protective finish of your choice.

Sign and date the piece and enjoy the moment of accomplishments and satisfaction.

A little artwork can add a personal touch to the piece.

Whether you are a beginner or a seasoned woodworker, the illustrated mass-production techniques will help you in any future projects that are to be made in large quantities. So, there you have it—an amplifier that enables you to enjoy an enhanced listening experience in or out of your shop.

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