Fairly manual monobore design guide below
Designing in special bores sounds extremely rewarding, but also extremely hard for hobbyist.
My current plan is just so that I don't have to dremel out any material when building the CIEM.
Has anyone tried making 3 bores version of the MASM 7?
3 bore is certainly possible, although it depends on your ear. I can do 5 tubes, or 3 2mm ID’s. The typical ear, with some practice on a dremel, should be able to do 2 2mm ID + 1mm ID, for the woofer part of MASM7.
I had an idea a while back, that although I havent tried, is the solution to an EASY monobore, that matches from left to right. Usually, I will at least prototype something before I right about it, but as they are the new cool to talk about, here we go. Everything works in theory.
What you need:
Krystallloid negative of an impression
Heat gun
Small drill bit (size TBD)
Wooden dowel (same size as drill bit) + fine pen + caliper OR
3d Printer
Step 1: Use the Heat gun to heat up the back side of your drill bit. Metals, especially tool steel, are generally quite thermally conductive, so you may want to holy the bit with a pair of pliers, as it will get hot. Poke the hot drill bit from the base of the negative in to the canal. The krystallloid melts very easily. Be sure to hold it upright, and occasionally remove the drill bit from the negative, so that the molten krystallloid flows out the base, not into the canal.
Note: When casting your negatives, you will want to make the canal of your impression stand as close to vertical as possible, so that the drill bit will enter the canal evenly, and not have any thin walls. You can prop the impression up with hot glue.
From here, you have a krystallloid negative with a massive hole in it. Ha! sucker! Go make another one, and dont be so gullible next time
Just kidding. From here, you have two options for plugging. Either A: Put the dowel into the hole (after making sure they are the same length, the volume is important) and cast with fotoplast, or B, 3D print something to fit inside the monobore, with a base the size of the drill bit.
With the 3d printer, you can incorporate a looooong horn, or a support for something like the 30019.