DIY Custom IEM

[jjgoertz]

I've never really found an earpiece that I've been comfortable with so I decided to make my own.

The process started with a set of Radian's custom earplug kits, a two part rtv silicone you mix together and shove into your ear to let it cure. From this you end up with a soft blue cast that feels like foam rubber. This will be the master for the female mold.



I then took the master, sanded the edges smooth, attached it to a jig, and dipped it in paraffin wax, heated to about 250F. Pre-heating the master before dipping it helps to get a more even coating. The wax serves two purposes, it helps smooth out the texture of the master, and it will be the release agent.



The jig hangs the master far enough into a cup to minimize how much mold material we need to use, but far enough off the bottom to give 1/2" of space around the master.



The mold material I used is Oomoo 30, a two part silicone. It's advertised as not needing to be vacuumed, but if you don't want to do a bunch of sanding on your parts after casting it's really necessary. Here's the mixed material in the vacuum chamber.



And here's the finished mold. It cured overnight at room temp, and was then cooked for several hours at 180F.




And this is the first mold I made before deciding to buy a vacuum chamber. Can't ever have too many tools. You can get usable parts from this mold, they just need extra sanding.

[jjgoertz]

Re: DIY Custom IEM

For casting the final parts I use Alumilite water clear, a two part clear resin. The resin also needs to be vacuumed or you will end up with little champagne bubbles in your final part. Before casting I preheated the molds to about 150F, and then slowly filled them via syringe. No release agent is needed because the resin won't stick to the silicone. I let the parts cure at room temp for a couple hours, and then baked them in the mold at 170F for a couple more hours.



After that post cure in the oven I'm ready to de-mold. I just pull the mold down around the edges to break the seal, get ahold of one edge of the cast part and lift it out of the mold. It's now ready to have the top edges de-burred. That's the point where I stopped on the first set of parts to be used as custom ear plugs for work.



For the IEM drivers I'm using Meelectronics M6 Pros, primarily chosen because they are small, thin, and the cable comes out the front.



I then routed out a pocket for the IEM to fit with a dremel and an abrasive bit. The pocket could have been significantly more simple if you removed the canal tube from the ear bud.





And finally the driver is attached and sealed with hot glue, being careful not to obstruct the canal tube.



Replicate for the second driver.



And you have the final fit for your custom IEMs.



So far they seem far more comfortable and secure than any regular tips I have found.

Total cost for the project was $10 for the earplug kit, $30 for the mold, $20 for the casting resin, and $50 for the drivers. If you want to include the vacuum chamber and pump that's another $250.

[dynamo]

Re: DIY Custom IEM

Wow, that is great work and creativity! It's cool to see some non-traditional audio projects and ideas like this from time to time.

[Uncle Bob]

Re: DIY Custom IEM

The best part is that they are custom fit for your ear! Great job!

[stook1]

Re: DIY Custom IEM

that's really cool! I have a pair of Mee A161P IEMs that I really enjoy. Not custom fit but they sound great. Anyway, very nice DIY effort.

[jjgoertz]

Re: DIY Custom IEM

Thanks for the encouragement, but now that I've spent a bit of time with these I think I might need to go in a different direction.

They are comfy, so that's a plus, but the seal needs to be improved for better isolation, and the frequency response is basically garbage. The seal is an easy fix, I just need to coat the canal piece with something until it fits. The frequency response seems to be inherit to the headphones, and not due to the custom tips.

I wanted to get a relative measurement between a couple pairs of headphones I have, so I modified my first mold to fit on my measurement microphone.



And here's the measurement set-up. This won't give us a true frequency response as interpreted by your ear, but we can look at relative measurements between sets of headphones.



Here's the results. The lime green line is the closest thing I have to a reference for earbuds, which is a pair of JVC FX35 Marshmallows with memory foam tips. To my ears they sound relatively flat with being 5-7.5 dB hot in the low bass.

Everything below that is the Meelectronics M6 Pros with different tips. 2nd from the top is the memory foam tips on the M6s, which is basically a perfect seal. 3rd from the top is triple flanged silicone tips. The bottom one is my custom tips, which have the worst seal.



Basically, in a best case scenario if I upsize the ear canal till it's a perfect seal, and account for the JVCs being too hot in the bass, these headphones are 15 db down from where they should be from 500Hz on down.

So, does anyone have a suggestion for a better ear bud in a size and layout that would work for this?

[jjgoertz]

Re: DIY Custom IEM

Just for fun I measured my over the ear headphones with this thing, Everything is normalized at 1000Hz.

Purple: Sony MDR XB-700
Baby Blue: Razer Orca
Green: Grado SR325
Orange: Beyerdynamic DT880 600ohm
Dark Blue: JVC FX-35 ear buds
Red: Shure SRH840