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Last summer, I asked a few questions about exponential horn design and construction for a homemade EMG copycat, and as I have finally begun construction of the horn, I thought I would post a follow-up to my previous topic. (Pictures are included below.)

I settled on a two-piece question mark-shaped horn (similar to EMG's Export machines) with a 100 Hz. cut-off frequency and approximately 27” mouth, HMV re-entrant style tone-arm (as used on the 130, 163, etc.), and portable Orthophonic soundbox—the mouth is smaller than Modern Gramophones says it should be for the rate of taper, but I’ve read that placing a large horn in a small room or in a corner enables the mouth to be made smaller without significantly altering the frequency response—and as my room is fairly small, a corner is probably the only reasonable place to put the finished horn, so the smaller mouth should work, at least in my current circumstances.

Following forum member Lucius1958’s suggestion from my earlier topic, I made a sectional former from Styrofoam, coated with shellac for smoothness, which meant that I spent most of my spare time last semester cutting, sanding, and gluing the pieces of the former (then sanding, gluing, and sanding again, and again, and again…); but the method does seem to be working. So far, I have successfully extracted the first and second sections of former from the horn using a mallet and a sort of Lego ramrod-thing, and have begun papering the third section—although removing this part of former will be probably be the hardest; it’s the longest curved section, and I had to design a ram-rod with two joints in it, so that it could reach around the first bend without becoming wedged in the horn!

I have about three layers (six sheets) of paper on the large bend right now, and plan to remove the former when I have about ten layers, then fasten the wood ring that will join the “neck” portion to the mouth, before adding another ten layers—it isn’t a quick process, although the horn is long enough now that by the time I’ve added a whole layer, the end where I started is just about dry enough to start the next. I can probably add another layer or two to-day, so if I can keep up a rate of two or three layers per day, I should be able to remove the next section former in a few days.

EMG = Ethan Makes a Gramophone (I love this horn, btw! Hope everything turns out well)

shoshani wrote: Thu Jun 10, 2021 12:46 pm EMG = Ethan Makes a Gramophone

That's a good one.
........................

Ethan,

You are doing a whiz-bang job on this.
The shape is artful.
Did you take any photos of the interior of the horn?
What is the average thickness of the horn?

James.

Ethan,

I am impressed! Yours is going to come out much better than the one I made! I like the way you are slowly making the swan neck and removing the former as you go. What kind of paper are you using?

I think it is time to go back to the drawing board and start mine over again

David

Nice work!

- Bill

Marvelous! Keep us informed as you go!

Thank you all for your comments!

Roaring20s wrote: Thu Jun 10, 2021 1:12 pm

shoshani wrote: Thu Jun 10, 2021 12:46 pm EMG = Ethan Makes a Gramophone

That's a good one.

Agreed!

dzavracky wrote: Thu Jun 10, 2021 1:37 pm
I think it is time to go back to the drawing board and start mine over again

Do update us as you make progress; homemade horn projects are always interesting!

Here are a couple pictures of the interior (before I began work on the large curve):
So far, I’ve been using two types of packing paper; a thinner, smoother white paper for the inner surface and thicker, sturdier brown one for the main structure—it seems roughly comparable to a paper grocery bag, which I’ll probably have to use as well, as I haven’t much of the brown paper left.

The current thickness is about ⅛”, but the final thickness should be around ¼”—at ⅛”, it seems sturdy enough to remove from the former, but I figured that another ⅛” of layers over the whole neck would make it less likely to resonate, sag, or break where I joined the sections. (I’m also planning to make a plywood keel that goes from the spigot flange to the neck-mouth joint, to help prevent sagging.)

I added another layer yesterday, this time using strips along the horn instead of around it—I haven’t done any preliminary experiments, but it seems as though having paper strips both along and around the axis should increase the horn’s strength.

That looks excellent, well done! Looking forward to seeing how it comes together!

It looks resistant and nice. Have you thought about leaving this aspect in the external surface? It looks great! Seems kind of a snake skin paper... and looks so smooth and bright!

Orchorsol wrote: Fri Jun 11, 2021 1:10 pm That looks excellent, well done! Looking forward to seeing how it comes together!

Thank you! I'm looking forward to that too, although somewhat cautiously--I haven't made any prototypes since my initial "test tubes" last summer, so it's all very experimental.

Inigo wrote: Sat Jun 12, 2021 8:05 am It looks resistant and nice. Have you thought about leaving this aspect in the external surface? It looks great! Seems kind of a snake skin paper... and looks so smooth and bright!

Thanks! I had considered using the brown paper as the outer layer, but I ran out of it to-day, so I guess I’ll be using something else—probably white or off-white, or a possibly a reptilian pattern, similar to what EMG used. The smoothness/brightness in the pictures in my last post is probably just a thin layer of glue; the paper is actually just a dull, solid brown, but it turns darker, especially around the edges, if it’s pressed after being dipped in glue water, hence the mottled appearance—I rather like the effect, although as there are only a few small scraps left, I suppose that’s irrelevant at this point.
I’ve had to wash some “new” records and do some yardwork since my last post, but I was able to add almost two whole layers:
As mentioned above, the brown paper that I had been using ran out to-day, and nothing else in my stash works quite as well—most of it is a little thinner and more prone to pilling or tearing during application; I think I’ll probably end up buying something thicker—Does anyone have any thoughts on using an all-cotton 80 lb cardstock? The thickness would probably be closer to what was used in real EMG/Expert horns, but I know that cotton fabric tends to stretch slightly under tension, so if cotton paper acts the same way, it might not be such a good idea for a horn, especially at the neck.

I tried extracting the former this morning, but without success; I think the inherent flexibility of Legos made the “ramrod” act more like a shock absorber, so when I struck it with a mallet, it just compacted against the foam—I might try making a wood version, but if that doesn’t work, I’ll probably end up carving out the former.