Acoustic amplifiers are pretty cool, but my favorite style is the Gramophone ... they just look cool ... especially when real metal horns are used. That being said, have you seen the asking prices for these creations? I thought the $185 model on Etsy was painful ... until I saw another for $495 ... OUCH!
I briefly looked online for metal horns, but those were starting at $50. I then tried to source a horn from a friend, but he rescinded permission to "borrow" it once he learned of my plans to "mutilate his instrument."
I toyed with the idea of using paper templates, cutting out sheet metal, forming, and then braising all the parts together, but I don't have that equipment ... yet.
I wanted to use something that anyone could easily acquire and the reoccurring inspiration was a funnel, which are abundant, but I couldn't find one I liked. That is ... until the day I was strolling through Walmart buying boring day to day life items.
Update: This project was featured on the Genius! section of bobvila.com
Step 1: Fabricating the Horn
There it was ... calling out my name. "Bales ... take me home .. I only cost $1.87." How could I refuse? It isn't everyday I get an offer like that.
I needed a fitting to hold the funnel at an angle and I decided on a 1 3/4" 45 degree copper elbow. PVC fittings are cheaper, but the walls are thicker and I wanted a smoother or lower profile transition. I would also have to faux paint the PVC, whereas the copper was already finished.
Using the bandsaw, I cut the funnel off at a point where it just fit into the copper elbow. The cut was cleaned up and the fit fine tuned on the orbital belt sander. I also roughed up the plastic with sandpaper so paint would adhere.
The copper elbow was bonded to the funnel using two part epoxy.
Step 2: Cutting the Box Parts
The resonator is nothing more than a box with mostly mitered sides made from Poplar. Box joints would look pretty cool I think, but I don't have a jig for cutting those ... yet. Dovetails would be awesome. Even pallet wood and butt joints would look cool for that rustic feel.
Since the 1" x 8" was too wide to cut cleanly on the miter saw, I used a large crosscut sled to cut rough lengths. The sides were then ripped to rough width.
Step 3: Cutting the Rabbets
The bottom panel is a removable piece of hardboard attached with a few screws. The reason for this is so I can experiment with dampening materials and/or acoustic chambers.
In order to accept the recessed hardboard, I cut a rabbet into the bottom of each side panel.
Step 4: Cutting the Side Miters
The side miters were cut on the table saw using a miter sled. I used a stop block when cutting the final length to ensure the opposing sides were equal.
Step 5: Cutting the Top Miters
The top miters were cut on the table saw using the rip fence. I also decided to employ a method I saw Jimmy DiResta use, which was a splined miter joint. Not only do they assist alignment during glueup, but they also strengthened the joint.
Step 6: Glueup
Thanks to the splined miters, gluing up the sides was achieved with a band clamp. The top however, wanted to slide around a bit, so I added a few vertical clamps and one horizontal clamp across the middle to prevent any bowing.
You could add splined miters to the top, but I didn't think I'd need and knew they'd add complexity to the overall glueup. That being said, I'll probably try it in the future.
Step 7: Drilling for the Horn
In order to hold the horn, the top of the box needed a 1 3/4" hole to accept the copper fitting. I used a forstner bit and drilled down about 3/8", which is half the board thickness.
We need a through hole for sound, but we also need a shoulder to support the copper fitting. I switched out to a 1 3/8" bit, which gives us a 3/8" shoulder. Location of this hole is up to you, but just be mindful of your side thickness. You can see I marked 3/4" in from the sides so I could avoid any mistakes.
If you've seen my other instructables, you know that I like to set my bit to just touch the backing material, so that it it just barely penetrates the opposite side. I then flip the stock over and finish drilling the hole. It's an extra step, but it's quick and eliminates all blowout.
Step 8: Routing for the Phone
To cut the slot for the phone, I used a trim router with an edge guide. The width of this slot, and therefore the diameter of bit used, will depend on the width of your phone. I personally went without a case for a minimalist look and a 3/8" straight bit did the job. For depth, I went about 3/8"-1/2" deep.
Just like the horn, we need a through hole for the sound, but shoulders to support the phone. I used the locations of the speakers to determine this layout. I then marked these stop points with a forstner bit because I wouldn't really be able to see the bit, but I would be able to feel the difference in material removal .. that may or may not make sense.
As before, location of this slot is up to you, but just be mindful of your side thickness. I chose my location soley based on visual appeal.
Step 9: Corner Splines
I wanted to use corner splines for decoration, but they also add strength to a miter joint. Internal and external miter splines ... this box is solid.
To cut the slots, I used my shop made spline sled, which is based off of the Eagle America jig. 1/8" strips of red oak were ripped on the table saw, cut into triangles on the bandsaw, and glued in place.
Once the glue was dry, the excess was trimmed off using the bandsaw.
Step 10: Sanding
The corner splines were sanded flush using the Oscillating Bent Sander, sides and top sanded with an orbital sander, and the sharp edges of the box eased by hand.
Step 11: Oiling
Finishing was rather simple.
1. One coat of 50/50 boiled linseed oil and mineral spirits to enhance the natural wood grain and coloring.
2. Several coats of lacquer (I don't recall how many and apparently forgot to take any pictures).
3. Wet sanding with 400 grit wet/dry paper.
4. Renaissance wax followed by buffing.
Step 12: Painting the Horn
I'm too cheap to buy a metal horn ... that doesn't mean I can't make a horn that looks like metal. If you know the price of Sculpt Nouveau finishes, you're probably yelling "you idiot" at the computer screen. Normally, I would agree with you, but I purchased these finishes for custom drums. Side projects like this are just a bonus in my mind.
Anyway ... the funnel was prepped with a coat of plastic primer, which comes in a rattle can and I acquired from Lowes. Next was a coat of a copper metal coating. The long direction didn't work, so you can see I switched it up for the second coat. This direction kind of makes it look like spun copper.
The horn looked great at this stage, but I wanted that green patina on mine. To achieve this, I misted on Sculpt Nouveau's patina solution while the third and last coat of metal coating was wet. I then stuck the horn in an upstairs closet to let humidity aid the process.
Once I was happy with the level of patina, I sprayed on a few light coats of lacquer to seal in the finish.
A few things to note:
1. The patina will smear/rub away if you touch it ... trust me.
2. The lacquer did reduce some of the patina .. dissolved some of it basically. That was a bit of a bummer, but still a pleasing result nonetheless.
Step 13: Glamour Shots
The horn attaches with a friction fit, which is great because that makes it possible to adjust the orientation, as well as making packing/shipping/moving easier.
In it's current state, the sound isn't great - mostly mid frequencies. I'm going to experiment with polyester stuffing, as well as creating chambers with hardboard ... like you'd see in a bass box or in those wave radios.
This project could easily be scaled up or down for different phones and tablets. Different funnels or other creative solutions for horns would totally change the look.
Top: 12" x 7 1/4" x 3/4"
Long Sides: 12" x 2 1/4" x 3/4"
Short Sides: 7 1/4" x 2 1/4" x 3/4"
Router Bid Diameter: 3/8"