Asselin.Engineer

DIY Silicone Custom In-Ear Monitors (CIEM)

2018/02/17
music ece star
Last Update: 2018/08/16

CIEM are custom fit headphones. In-ear monitors custom fit for your ears. They are great for sound isolation and allow superior sound quality.

Our goal is to build our own pair of silicone pair of in-ear headphones, by buying parts online and DIY.

On this page, you can read on why we chose to DIY and why silicone but this post is mostly a journal of our results, successes or failures. To show how we built our custom in-ear headphones, there are some instructions, explanations of some choices, details and many pictures.

This post was written because we could not find any resource on making silicone CIEM. While there are some acrylic tutorials, most are incomplete, outdated, and don't talk about materials and where to get them. A large part of building CIEM is similar for acrylic and silicone.

If you have any questions or want more details, contact me by email and I will update this article.


Why DIY CIEM?

Cost

CIEM are not cheap. Price range is 400$ to 2500$. Cheapest set I could find: Custom Art's FIBAE 1 at 400$. Noble Audio's cheapest are 600$. Additionally, impressions and shipping fees will cost 50$ to 200$. Finally, using silicone instead of acrylic is usually a premium of minimum 200$.

Fit degradation of previous pair

I've had a set of custom-fit acrylic headphones for 4 years now. Unfortunately, the fit is not perfect anymore. The outer ear, which includes the ear canal, changes with age and weight.

For sound isolation, an airtight seal is required. My pair cannot offer a reliable seal anymore.

I've seen people use nail polish or foam wraps (Comply Custom Wraps) as alternatives to a complete reshell. I tried custom wraps but they also degraded after a month of use.

It's not that hard to DIY

To get a set of CIEM, you first select which model you want and buy it.

After, you'll have to get your ear molded by an audiologist (or DIY like shown below) and send the resulting impressions to the CIEM manufacturer or artisan. This can cost up to 150$.

When the manufacturer receives it, they send it to their artisan (usually in China) where they will make your CIEM. Finally, in 1-8 months, you will receive the final product. If you are lucky, there won't be any duty fees.

CIEM Acrylic Orange

After hours of research, reading threads on HeadFi, /r/DIEMs, tutorials on ear impressions, molding agar, acrylic, silicone, drivers, etc., we figured it could be done.

Why Silicone CIEM?

Good:

  • Not seen often, usually regarded as a premium.
  • Better fit because of material elasticity. Silicone should also be more comfortable.
  • Sound Isolation of silicone CIEM is better than acrylic.
  • Completely filled case offers better isolation. Hollow shells cannot be made with silicone because of the final hardness of the material. It is too flexible. (Acrylic is hard and silicone is silicone)
  • DIY cost of acrylic is similar to silicone. Buying silicone CIEM from a manufacturer is 200$ more.

Bad:

  • Harder to position electronics. They have to be precisely positioned in the mold, before filling it completely with silicone. With a hollow shell, drivers and wires arrangement can be modified before sealing the cap, which is not possible with silicone. This means perfect frequency response cannot be guaranteed by modifications from a frequency analysis (There are possible solutions to this).
  • If electronics fail or are not properly positioned, they can only be salvaged by destroying the silicone.
  • Silicone CIEM are known to be less durable than acrylic CIEM.
  • Detachable wires are less frequent with silicone CIEM.

Part 1: Silicone Ear Plugs

Material

All required material can be bought from oundLink. SoundLink is a shop on AliExpress and they know their shit. I contacted Grace many times to make sure I was getting the right stuff and she was always helpful.

When we bought bulk material, our total cost was around 400$ USD, including shipping.

Ear Impressions

Refined Impressions

  • X-Acto or sharp knife
  • Wax (people had good results with basic candle wax (plain paraffin wax)).
  • Small metal container with bain-marie or system to heat wax
  • Toothpicks

Negative Mold

Silicone And Lacker

Drivers and Tubing

Ear Impressions

ear impressions

There are single use impression kits available online. Including shipping to Canada, they cost the same as SoundLink's bulk material. We used Detax green eco.

DDetailed instructions can be found here. Everything ear impressions is further explained on this page. I suggest you read the first document, at least.

Make sure you are relaxed and your ears aren't swollen. (Mine are sometimes swollen after a shower and I can't fit my CIEM)

Ideally the impressions will show at least 2mm of the second bend inside the ear canal. The material should completely fill the canal. You might feel some pressure while it expands a little.

  1. Insert foam tip as far as possible inside your ear using a Q-tip. I inserted mine until it started to hurt.
  2. Bite on bite block.
  3. Mix the two parts together and fill the impression syringe.
  4. Insert syringe in ear and make sure to release the material deep enough to fill the canal completely.
  5. Completely fill outer ear.
  6. Repeat for second ear.
  7. Wait 10 minutes (follow your impression material instructions)

If you bought your CIEM, here is where it stops. Send your impressions by mail to the manufacturer.

Molding putty
foam block inserted
15 minutes later
diy ear impressions result
diy ear impressions result
diy ear impressions result
diy ear impressions result
diy ear impressions result

Refined Impressions

refined ear impressions

Extra material on the impressions can be trimmed with a knife, but you should keep as much as possible. Especially when molding for silicone CIEM. It is better to keep more material because we can later trim the shells before the final lacker application.

You can chop the tip of the ear canal but keep around the second bend, keeping the angle of the bend. Keeping the angle allows us to position the tubing to point deeper. Most CIEM do not have a deep canal because it can hurt. In our case, we can later chop the silicone while trying it on. You'll be able to maximize depth and minimize pain.

I initially did not trim the ear canal on mine and later had to use a bigger contained to create the negative mold. This makes it harder to remove from the negative mold, which eventually broke it.

Also, as you can read below, silicone ear plugs with longer ear canal doesn't necessarily deliver better sound isolation.

Furthermore, the outer ear can be shaped, making sure you leave enough volume for the cable plug. This is important. You'll be able to trim it more later when working the silicone.

At this point, you can try on your impressions, to help trim the extra material. Be careful to not break them. I had never heard about people trying their impressions on. We did and there were no problems. It is not required but it helps to trim.

It is harder than you think to put CIEM on for the first time. Impressions are even harder, mostly because of the long ear canal. By safely trimming the canal up to the second bend you should be able to try them on.

  1. Trim ear canal
  2. Trim outer ear
  3. Heat wax
  4. Dip impressions in wax using toothpick
  5. Wait 10 minutes

The goal of dipping in the wax is to cover any imperfections.

This is harder than it seems because the wax did not stick much to the impressions. I am not sure if this is worth it.

ear impressions
Roughly trimmed external material
I chose to trim the canal later
ear impression in ear
ear impressions in ear
Bowl is way too big but we can reuse the wax
melted wax
Impressions safely resting on banana
refined ear impressions

Negative Mold

Boiling a certain algae produces agar, which we use as a duplicating material. There are different materials available but agar is cheap, reusable and does the job.

Ear impressions in agar

Piercing holes in the inverse mold with a small drill bit will allow the silicone to completely fill the mold. We don't want any air pockets! It is easy to chop the extra silicone that escapes through the holes when filling. Drill holes wherever air pockets could form. Our best mold had as much as 8 air vents. Make sure the agar isn't too hot, otherwise the was will meld and mix with the agar when you poor it on the impressions.

  1. Get liquid agar by heating to around 90°C
  2. Let it cool to 45°C
  3. Place impressions in cup, external side down
  4. Pour agar in cup, completely covering the impressions
  5. Remove bubbles with toothpick
  6. Wait until agar is solid. (Around 30 minutes)
  7. Use a small drill bit to pierce holes in the agar
  8. Make sure no agar residues are in the mold
Solid agar
Liquid agar cooling
Mine were too big to fit. The second time we did this I cut the canal and it was worth it
This is hard and took a while but don't worry, you can melt it again if the mold breaks
Drill bit size
air vent in agar
Result. Extra silicone is easily removed

Silicone And Lacker

Silicone ear plugs lacker curing

This step is optional but it's a good introduction to silicone.

Get an injection gun. It is impossible to get the silicone our with your hands. Soundlink does not sell the cheap gun we used (yet). You can find them on ebay or Aliexpress for less than 10$.

The silicone cartridge can be sealed for later reuse. No need to empty it on first use. we had enough for 2.5 pairs with a single cartridge.

Also make sure you have the right mixing tips! Double check with Soundlink. They did not send us silicone mixing tips.

For this step, you'll definitely need a silicone impression gun.

Soundlink only has detax softwear silicone lacker. The lacker's viscosity is a bit higher than the wax.

  1. Insert silicone cartridge with mixing tip in the injection gun
  2. Inject silicone
  3. Let cure 2 hours
  4. Remove ear plug from agar
  5. Trim silicone
  6. Dip in lacker
  7. With toothpick add lacker droplets where there are imperfections
  8. Let cure for 24 hours to get rid of the smell
Get the right mixing tip
Get the 10$ injection gun
First ear plugs we made
Jaybird upgrade
After mixing two pairs of ear plugs. We reused this to make the smaller ear canal only plugs
Detax Softwear dip coat
Jaybird upgrade with antennas from holes
Silicone ear plugs fresh out of their agar inverse mold
needs to be trimmed
not trimmed yet
second batch: Ear canal plugs and jaybird upgrade with different angle. Notice silicone usage
second pair of jaybird upgrades
Dip in lacker
Curing stand
Result ear plugs. Ear canal + regular CIEM size. I sleep with those
DECENT!
Final result
Really proud
comfortable for sleeping

Part 2: Silicone CIEM

Drivers and Tubing

Soldered drivers

Driver selection is up to you. There is an infographic out there that I can't find anymore. It explains the popular driver combinations.

We chose to use a set of drivers sold by Soundlink for around 60$ each. They are the triple driver set GK-31732. Recently they added these: quad driver set GV-32830. I would get those.

The dampers we chose are BF-1861 (on tweeter) and BF-1921 (on woofer). This setup was recommended on multiple forum posts.

Spreadsheet of drivers used in popular CIEM on the market

Great visual reference on how drivers work

Knowles dampers reference

After choosing your drivers or schematic, solder it up to the cables.

Get a decent soldering iron and solder the litz wirers to the drivers. It was much easier to use helping hands than only blue putty. It is harder than it seems to solder the connectors! Apply some solder on them first before soldering the wires. This part is straightforward.

Our CIEM both had problems after 2 weeks. Nic's connectors broke and mine are buggy. They need to be wiggled on the left ear for sound to be good. I suggest you don't use connectors and solder directly to the cable. We chose to use connectors because we did not want to have to lose a set of cables if something went wrong. Unfortunately, both our headphones had problems with the wiring. Both problems were caused by the connectors.

That's why I suggest you just sacrifice the cable. Mold it in the silicone with the connectors. You should probably solder the cables directly to the litz wires. This removes a crucial problem with silicone CIEM. Aliexpress sells decent cables for 30$.

The tubing length can vary, just make sure they are the same between both drivers. We use a smaller 1mm tubing to plug in the driver and to a larger 2mm tubing. The larger tubing contains the damper. The dampere is secured by a second smaller 1mm tube. Keep this one long or you'll have a bad time when filling with silicone.

I believe the damper's side does not matter but just in case, we chose to put them like they are in my Noble CIEM; rounded edge is outwards.

Soldering station
Soldered driver
All drivers ready
All drivers sexy
Litz wire and connectors
Begin tubing
More tubing
All tubing added

Silicone And Lacker CIEM

Filling with silicone

Refer to part 1 for more information.

Make sure the tubing are symetrical on both ears. Drivers should not be touching the agar much.

When filling with silicone, make sure to fill behind and under the drivers!

After this step, the headphones should work but they will be ugly and harder to try on because of the rubbery surface of the silicon.

Chop the extra material on the impressions and cut the extra tubing. To apply the lacker, block the tubing holes with toothpicks and block the connector pins with some tape.

See part 1 for more information on silicone and lacker.

Ready to be filled with silicon
Drivers secured
That is why we need long tubing
Not filled yet
No bubbles!
Filled. Holding the wires so they have the angle we want
Getto setup holding the cables
Silicon used for a set of CIEM, including the mixing tip
Straight out of the mold
Removed extra material. Still ugly without lacker
Nice
Drivers almost coming out of the silicone. Lacker will fix this
Chopped tubing and toothpicks inserted to contain lacker during the dip. Also scotch tape on the connectors
Shape is sexy
Tools used for the lacker application
Clean the CIEM silicone before lacker application
Dipped in lacker
Removing imperfections by precicely adding small drops of lacker
Final result after lacker application

What's next?

The end goal is to build a set of silicone Bluetooth CIEM.

Bluetooth from apple airpods? maybe. (they are great) https://www.ifixit.com/Teardown/AirPods+Teardown/75578

Fine tuning with frequency analysis: https://www.reddit.com/r/DIEMs/comments/5sacyz/iem_tuning_guide_by_sonion/


If you have any questions or want more details, contact me by email!

You can also subscribe to this mailing list http://eepurl.com/du0jdb. I plan to update you on new projects once or twice per year.


References:

Complete acrylic CIEM video tutorial, DIYearphone: https://youtu.be/LJ55BCSwJkg (I asked if he was selling electronic kits again and he replied no december 2017)

Great HeadFi tutorial, zman0225: https://www.head-fi.org/threads/diy-shell-making-re-shell-guide-w-some-pictures-new-finished-ciem-pics.656122/

Impression instructions: https://web.archive.org/web/20170622074802/http://site.earplugstore.com/Making_Your_Impressions.pdf

Knowles dampers reference: https://www.reddit.com/r/DIEMs/comments/5d9d7x/diem_clone_of_etymotic_er4_for_43_parts_list/

Insane collaborative document with lots of information: https://docs.google.com/document/d/1jU37oWefx2dGS8dWw5TVkugEtwJh_bh3fuUBNe2HrQg/edit?usp=sharing/