Introduction: Leather Gramophone Horn, Passive Smart Phone Amplifier

I first got the inspiration for this project as a gift for my wife for our 3rd anniversary. I like to follow the traditional anniversary gifts. The only problem is that was two and a half years ago. I kept running into issues with completing this project as this is my first full leather project. I would get distracted and then life just put it on the back burner. The current leather contest reignited my inspiration and I was able to finish this for my wife.

"Happy belated 3rd anniversary babe!"

The main focus of this project it the leather gramophone horn. It is made up of 8 panels to create an octagonal shaped horn similar to the antique gramophones. Going into this I was unsure of the acoustical properties of leather. Weather it helps or hurts the sounds was not a huge concern. In the end it did amplify but not to the extent that other materials might. It does give the songs a nice old timely treble tone.

Step 1: Tools & Material

For the leather work the following are needed:

  • Veg-tan leather.
  • leather scissors or razor blade.
  • Swivel knife.
  • Diamond stitching punch.
  • Various stamps. (further description later)
  • Mallet.
  • Leather burnisher. (mine is hand made)
  • Adjustable stitch grover. (mine is hand made)
  • Curved needles.
  • Waxed thread.
  • Leather holding jig. (optional)
  • Garbage bag or some plastic sheet.
  • paper towels.
  • Satin finish.
  • Leather dye.
  • Wool applicators and/or daubers.
  • Disposable gloves.

For the copper pipe work the following are needed:

  • Variety of 3/4" copper pipe and fittings.
  • Copper pipe straps.
  • Copper nails.
  • Blow torch.
  • Solder.
  • Flux.
  • Pipe cutter.
  • Rubber mallet.
  • Hole saw.
  • Dremel.
  • Hack saw.
  • Plumbers wire brush.
  • Polishing wheel.
  • Polishing compound.

Not shown in the pictures is some wood working tools needed:

  • Table saw/Jigsaw/Hand saw.
  • Router with bits. (Roman Ogee)
  • Sander.
  • Hammer.
  • Drill with bits.
  • Clear rubber cabinet bummers (for feet)

Step 2: Custom Holding Jig and Tools.

To take care of cutting the inner border of each leather piece and to hold the leather while stamping I made a custom jig. Print off the attached "Panel Pattern" PDF to make this jig. The pattern on the PDF has three copies of the same thing. Cut these out on paper. These will be glued to 1/4" plywood for pieces "A, B, & C" from the pictures. I like to use spray glue for this. For cutting I like to use a scroll saw but a band saw, jigsaw or coping saw can be used.

For piece "B & C" first cut (2) 6"x10.5" rectangles out of the 1/4" plywood. Glue one pattern onto each piece centering it in both directions. It doesn't need to be perfect. For piece "A" use the remaining plywood.

When cutting out piece "A". Follow the outer solid line cutting away the wood on the outside of the line. Do NOT remove the pattern after cutting this out. You'll still need it.

When cutting out piece "B". Follow the inner solid line cutting away the wood to create a "hole".

When cutting out piece "C". Follow the outer solid line cutting on the inside of the line to create a "hole". This will be a negative of piece "A".

One thing to keep in mind while cutting these out. Piece "A" will need to fit into the hole that you cut for piece "C" like a puzzle piece. You don't want to much play between the two. Some sanding may be needed to make them fit together.

To assemble the jig first insert piece "A" into piece "C". Piece "A" will be used to align piece "B" to "C". After apply wood glue to the surface of piece "C" align the hole of piece "B" to the inner solid line of piece "A". Clamp the two pieces together and double check that they are still aligned properly. Remove piece "A" to ensure that it doesn't get glued to the pieces "B" or "C". Set aside to dry.

As a note, there were two tools that I needed to make because my local stores were closed due to the pandemic and ordering them would have taken to long. These items are a leather burnisher and an adjustable stitch grover. They are crude but they got the job done. They are included in the pictures.

Step 3: Cutting

With the jig dried, you can move on to the beginning of the leather work.

Use piece "A" to cut out all of your panels. There are a few ways to do this; 1) Use piece "A" to transfer the pattern onto your leather by either a pencil or use a razor blade to lightly score the leather. From there you can continue to cut through the leather with the razor blade making many light passes tell its cut through. 2) If you have leather scissors use those. Lastly, an unconventional way that I ended up using was to cut with my scroll saw. I cut with the blade partially into a piece of wood as a backer for the leather. It gave me nice clean cuts with better control then a razor blade.

Cut out the attached "Flower Pattern" PDF in paper to transfer it to the leather. From here on when ever you are making any impression in the leather you want to always wet the leather, I used a wet wash cloth. The top needs to be wet while keeping the bottom dry. As you notice the leather start to dry go ahead and wet it again.

To transfer the pattern, place the pattern in to the jig with the leather behind it. Using leather stylist or some soft pointed tool, lightly trace the lines. You have to finish some lines outside the jig if the jig interferes with the stylist. This will leave an impression in the leather. It doesn't take much pressure to do this. Remove the pattern from the jig and replace the leather panel. With a swivel knife make a cut around the border of the jig to create the inner border of the panel. Only cut into the leather no more than half way. Remove the panel and cut along the lines of the pattern you transferred onto the leather.

Step 4: Stamping

Now it is time to start stamping the leather. Start with a steep bevel tool. Position the bevel tool on the outside of the line with the lower point against the line. Move along the line with light strikes from a mallet moving half the width of the tool then come back across the line with heavier strikes. Do this for all the cut lines of the flower. Move to a shallower bevel tool for the border positioned on the inner side.

Next move to a seeder tool to stamp the shape of the spadix in the center of the flower. Four stamps did fine for me.

Next move to the pear shader tool. This is used to give depth and shade to the design. Us it along the inner side of the pedals and the leaf or any where you feel you need shading.

Next move to the background tool. This tool just breaks up the background of your scene. They come in different sizes. As you move around twist the tool in your fingers to break up the pattern. I would stop the stamp as I came to the bevel of the border for nice look. To finish of the design use the swivel knife to cut the veins of the leaf in.

Before moving on to dying, Use a burnishing tool to give the top edge, the one that will be the opening of the horn, a nice smooth rounded look. Make sure to wet the leather before doing so then rub the tool back and forth along the edge. I was able to leave my hand made one on my lathe to burnish as it spun. You could use a drill press as well. Doing it by hand will just take longer.

The last thing to do is the punch in your stitching holes. This is best done on something like scrap wood that you don't mind getting tiny holes in. With an adjustable stitch grover cut in a grove about an 1/8" from the two long curved edges. My homemade grover didn't actually cut instead it just left an impression. Either is fine for this project. With a diamond stitch punch start with the first tooth just barely handing or the edge and the rest of the teeth inline with the grove. Now move down the grove with the first tooth in the last hole you punched. This keeps the spacing correct. Continue until the end of the grove. Do this flower design for four of the panels. the other four panels just need the border cut and beveled.

Step 5: Dying

Prepare for dying your leather by covering your workspace with a garbage bag or some plastic sheet. This will protect the surface your working on. Cover that with paper towels so there's less slipping around on the plastic. Don't forget your gloves and some paper towels to wipe off excess dye.

I found a good combination of a clear satin finish with a gel antique dye in saddle tan.

Start with the design face of the leather. Apply the satin finish with a wool dauber and wipe off the excess. Then move to the dye immediately after. You can use another dauber or a wool pad. It doesn't take a lot to get the dye on. Less is more when using the dye, I think on a few I used too much. Wipe of the excess. After the dye has dried, move onto the back and edges using the same process. Things can get messy so you might have to wipe off the design face again.

Leave to dry overnight.

Step 6: Stitching

The process of stitching will start with stitching four pairs of a flower panel and a blank panel. It is important the the flower panel is stitched on the same side ever time weather on the left or right. If not you will get two flower panel next to each other. Unless that's what you're going for.

Most of the stitching will be done from the back side of the panels. You will be using a baseball style stitch. Start with about six feet of black waxed thread. Thread a curved needle onto each end the thread.

With two jointed panels start the stitch at the big end. Push each needle through the first hole on each panel from the back side. Cross the threads and come back through the same holes. From here on out the needles will pass between the panels and back through the holes from the design face. With the panels on your lap, big end towards you start with the right thread and push the needle between the panels and come back through the next hole on the left panel. Repeat with the left thread but come up through the right panel. Move back and forth like this always tighten up your stitches as you move. Once you reach the end, finish off with a square knot. Once the pairs are stitched together, stitch those pairs into halves and then those halves into the finished horn. The last line of stitch may be cumbersome but with patience is doable.

This horn is design to connect with a 1" to 3/4" copper reducer. Push the reducer, small end first, into the opening opening of the horn. Push it into the narrow portion until the small end sticks our the end of the horn. This should be a pressure fit. To help keep the narrow end tight rap a length of waxed thread around the outside of the narrow end and tie it off to keep it secure.

One byproduct of the stitching process is some un-dyed leather is exposed around the stitches. Use a small paintbrush and some more dye to touch up those spots.

Step 7: Copper Pipe

The layout of the copper pipe is up to your personal design. I went with a basic design to position the phone next to the horn opening.

Most of the the joints will be soldered together to keep everything solid. I kept two joints loose. One is the reducer connected to the horn and the 90 degree street elbow. This allows the horn to be removed for repairs, replacement, etc. The other joint is the phone cradle. As of right now the two phones being used with the amp has their speakers on the right side. If future phones used have their speaker in a different spot the old cradle can be swapped with a new one.

For the rest of the connections, use a plumbers wire brush to clean and scuff up both ends of the joint. Apply flux to the female end. Push the fittings together. Heat the joint with a torch with your solder ready. When you feel the joint is hot enough remove the torch and touch the solder to the joint. It should melt the solder and wick it into the joint. Ensure the solder gets all the way around the joint.

If you have a 90 degree elbow turning up into the horn, do a dry fit to get the proper angle. For a 90 degree elbow turning straight up, use a square on the side to angle it up.

The phone cradle is made up of a tee and a short length of straight pipe. I cut the top half of the tee off with a hack saw. You will use the piece with the tee on it. To get a straight piece to lay flush in the cut opening, the ridges that kept strait pipe from pushing into the tee needed to be removed. A Dremel with the grinding bit does nicely. Cut a piece of straight pipe long enough so that once soldered to the tee it will position your phone's speaker over the bottom tee hole. Make a cut with a hack saw on the front side of the cradle that is flush with the cut on the tee (see picture). Use a pair of needle nose pliers with the teeth wrapped in electrical tape to protect the copper to open up the cut flap of pipe. Once opened up far enough use a rubber hammer to flatten the flap of copper. Position the flap just past vertical to hold the phone upright. Use a hole saw the same size as the opening of the tee to drill though the blocked hole of the tee. Grind down any sharp edges or corners.

To clean and polish up the copper from soldering I used a buffing wheel with compound and wipe down with a clean cloth. I used those clear rubber cabinet bumpers at the top of the flap on the cradle to protect your phone from the hard edges. A strip a sticky backed foam would do too.

Step 8: Wood Base

The base can be from any wood and any size to fit your needs. I believe the wood I used is curly maple. Cut a radius into the front two corners on band saw. You can leave the edges square or route off the profile into the top edge. I used a Roman Ogee bit in mine. I sanded all surfaces smooth. I burned in my brand before applying three coats of clear gloss spray lacquer.

Step 9: Final Assembly!

For final assembly, dry fit the horn and pipe to center them on the wood base. When you find a good spot use copper pipe straps to hold the pipe down and use copper nails on the straps for a clean look. I drilled a small pilot hole to make sure I did not split the wood. Because the wood I used was not quit deep enough, two of the straps needed one of the tabs cut off. Finish with more of the clear rubber cabinet bumpers as feet on the bottom of the wood base.

Thank you for your interest in my Instructable. This was a learning experience especially with the leather. I have so much more to learn. If you feel it is worthy, I would appreciate a vote in the leather contest. Thank you.

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