Matt McCutchen's Web SiteMaximum noise isolation for truly wireless earphones  (Top, Introduction, Design overview, Usage, The adapter, The mold, Bottom).  Email me about this page.

Maximum noise isolation for truly wireless earphones

This page describes my procedure to modify the Doppler Labs Here One and Bragi Dash (and Headphone) truly wireless earphones for maximum noise isolation.  You can try it for yourself; read on for details.  A few photos to pique your interest:

Assembled Here One earpieces: view of the side that faces out of the ear.
The Here One earbud, mold, adapter, and foam tip spread apart.


I appreciate earphones with excellent noise isolation: they make it possible to hear audio in good quality at moderate volume, and I can leave them on with no audio playing just to block outside sound, since I'm easily bothered and distracted by noise.  (I prefer the in-ear form factor for the light weight and portability.)  I was lucky to stumble upon Comply P-series foam tips in 2008 and have used them with compatible earphones ever since.  Since 2012, my preferred wired earphone model has been the Shure SE115 (and its successor the SE112) for the excellent fit and isolation at a reasonable price.  As lightweight wireless earphones began to become widely available, I was interested in their convenience, but the prospects for achieving the level of noise isolation I wanted did not seem good; part of the problem may be that my ears have an unusual shape.  In addition, putting on earphones with foam tips takes both hands and about 15 seconds to get a proper fit, and it felt tedious to take the earphones off and put them on again if I wanted to hear the outside sound for a brief period such as a transfer between two segments of a public transit trip.

Finally, the Bragi Dash emerged in February 2016; it is "truly wireless" (two earbuds with no wire between them) and has the ability to feed through the outside sound ("transparency"), which can be switched on and off without removing the earbuds.  I decided the advantages were compelling enough that I would buy a Dash and attempt a custom modification to get the level of isolation I wanted: 3D-printing an adapter for Comply tips, as suggested by a commenter on the forum.  I made significant progress toward a satisfactory long-term solution for the Dash, but before I got there, I moved on to the Doppler Labs Here One for its additional noise filtering features.  With a little further development, I reached a solution in late May 2017 that has served well enough that making further improvements has fallen down my priority list.

I'm excited to publish my procedure to offer what I hope will be a good solution to people with similar needs, while we wait for manufacturers to prioritize providing maximum isolation for a wider range of ear shapes out of the box.  This page describes both my current design for the Here One and my design for the Dash at the point that I stopped working on it; I confirmed that the Dash design also applies to the Bragi Headphone since it is the same shape as the Dash.  As of 2018-04-14, the Here One is no longer being manufactured or supported by Doppler Labs, but plenty of units are still available for sale online.  The Dash has been succeeded by the Dash Pro; I presume the Dash Pro is the same shape (so the Dash design would work) but have not confirmed this.  Similar techniques may work for other earphones, though if you don't specifically want the features of the Here One, Dash, or Headphone, I'd suggest you look for an earphone model that meets your noise isolation and other needs with off-the-shelf parts before attempting a custom modification.  New options are bound to become available over time, but unfortunately it isn't trivial to find them; as of 2017-06-24, the Comply web site doesn't have a way to browse all the earphones compatible with P-series tips.

I've described the main pitfalls I'm aware of, but use of this procedure is ultimately at your own risk.  My experience so far suggests that you should be prepared for several rounds of trial and error at a cost in time and money, though hopefully fewer than I went through.  Good luck, and please let me know how it goes (by email or on the Here One forum thread) so we can provide better information to future users!  I have a stockpile of old parts that I would consider sharing, and I'm open to arranging "group buys" of parts if it makes sense.

There are various easier modifications described on the Dash forum (and as of 2016-10-08, a compatible Comply tip model), which may provide enough noise isolation for some people, but I assumed they wouldn't be good enough for me and didn't try them, so unfortunately I can't report on the comparison.

Design overview

As I understand it, once an earphone blocks direct airflow into the ear canal, its (passive) noise isolation is determined by how tightly it grips the ear canal.  Incoming sound waves cause the whole earphone to vibrate, including the side that faces the ear canal, transmitting some sound into the ear.  The tighter the grip, the less the earphone vibrates and the less sound is transmitted.

A good grip starts with the use of a long foam tip such as the Comply P-series tip in the ear canal.  Then the earbud itself has to be secured tightly to the foam tip with an adapter that holds the earbud in the desired place in the ear.  (The tips of the Here One, Dash, and Headphone are too wide to fit into a Comply P-series tip directly, and in any case, the angle would be wrong for my ears.)  For the Here One adapter, I added a wide, rounded surface that presses against the bones inside my ear to tighten the grip, similar to the way the body of the Shure SE112 does, and this noticeably improved the isolation.  (My adapter for the Dash does not have this feature, but I see no obstacle to backporting the feature.)

Finally, a custom mold secures the earbud in the concha of the ear.  I found that when I use the wide adapter base, adding the mold improves the noise isolation only marginally, but it helps avoid pressure points and distracting looseness, and I like the more secure fit.  Without the wide adapter base, the mold does significantly improve noise isolation.  (The Dash fit sleeves serve the same purpose as the mold, but they won't fit as well as a custom mold, and in my case, all of the provided fit sleeves hold the earbud in such a position that the adapter doesn't fit in my ear.)

You can try a custom mold in combination with silicone or foam tips that fit directly on the earbud (such as the supplied ones), and for a relatively low cost in time and money, you may get somewhat better isolation than with the tips alone.  I needed the adapter to get the level of isolation I wanted.

Here is the full set of photos for the Here One:

The side of my head with the assembled Here One earpiece.
Assembled Here One earpieces: view of the side that faces out of the ear.
Assembled Here One earpieces: view of the side that faces into the ear.
Assembled Here One earpieces: view of the side toward the back of the head.
The Here One earbud, mold, adapter, and foam tip spread apart.

And for the Dash:

Assembled Dash earpieces: view of the side that faces into the ear.
Assembled Dash earpieces: view of the side toward the back of the head.
The Dash earbud, mold, adapter, and foam tip spread apart.


With the assembled Here One earpieces, casual tests in different noisy environments suggest that I'm getting isolation close to that of my standard, the Shure SE112, though I haven't tried to get access to the equipment to make precise measurements.  The earpieces are comfortable enough to wear for at least a few hours at a time.  Viewed from the front of my head, the earpieces stick out of my ears a bit more conspicuously than the stock Here One, which could be considered poor style.  It's a trade-off I've been willing to make for the greater isolation and more secure fit; I might be able to make the earpieces a little slimmer, but I haven't made that a priority so far.  Your results may vary based on the shape of your ears.

The adapters and molds have to be removed each time the earbuds are put in the case for charging and reattached when the earbuds are used again.  (The foam tips can remain on the adapters.)  You can store the extra parts in a small drawstring bag or case, as may come with earplug-related products.  The assembly and disassembly gets tedious, but compared to maximum-isolation earphones that don't support switchable feed-through, your trouble is paid back as soon as you use feed-through once or twice in situations in which you would have taken off the other earphones and had to reinsert them properly.

To reduce the assembly burden, when you take the earpieces off, you can leave them assembled outside the case.  There is currently no way to turn the Here One off outside the case, which presents several issues:

The Dash presents similar issues, though I don't remember all the details.  In contrast, the Headphone can be turned off, so it works nicely with custom parts.

I don't use the Dash activity tracking seriously and can't speak to the accuracy of the sensors when the Dash is fitted with the custom parts.

The adapter

The 3D-printed adapter consists of a base that snaps onto the flange on the tip of the earbud and a nozzle that goes into the core of the Comply P-series tip, holding the two in the correct relative position and orientation to fit your ear.  As mentioned above, the current version of my Here One adapter also includes a wide, rounded base that presses against the ear bones to tighten the fit.  In a previous version, and in the Dash adapter, the base is just large enough to cover the earbud tip.

To produce your own adapters, you can start with my CAD files (below), which have the correct shape of the base and the nozzle, but you will probably have to change the parameters that control the relative position and orientation of the base and nozzle to fit your own ears.  Finding the right parameters is a guessing game; be prepared to go through several iterations to get an adequate fit.  I initially had ear impressions made by an audiologist, hoping that by looking at the shape of the impressions compared to the earbuds, I could make a reasonable initial guess of the parameters.  However, this didn't work very well, in part because the impressions don't extend as far into the ear canal as the Comply tips need to.

The other tricky issue with the adapter is that it needs to be tight enough on the flange of the earbud to get good noise isolation, but it needs to be able to go on and off repeatedly without wearing out either the adapter or the earbud flange.  For most of my time working with the Dash, I used Formlabs Tough Resin, which fit tightly at first but ultimately wore down the flanges to the point that no adapter would stay on the Dash.  When I moved on to the Here One, I used Formlabs Durable Resin and tuned the parameters to a point that seems to work.  I suspect Formlabs Durable Resin may also work well for the Dash with the right choice of parameters.

Important note: The latest version of the Here One model has a hole that typically comes out slightly too small to go on the earbud, although this can be affected by variations in fabrication.  I've decided to leave it this way and scrape some additional material out of the hole in each adapter with a pocketknife until the adapter fits on the earbud, in the hope that I'll end up with a good fit regardless of variations in the adapters as fabricated.

CAD details

I designed the adapters using FreeCAD, which is quite buggy but has the advantage that others can get started on the project without the potential barrier of getting access to a licensed version of a commercial CAD tool up front.  Start with the CAD file of your choice:

(For the Dash, I eventually replaced the ridge with tabs in an attempt to make the Formlabs Tough Resin adapters go on and off the earbuds more easily.  But if you are starting out with Formlabs Durable Resin, you may be better off with the ridge, as my Here One adapters have.)

All of the parameters you are likely to need are in a spreadsheet in the FreeCAD file.  Since (as of 2016-07-02) FreeCad has no way to disable the recomputation of the whole document each time a spreadsheet cell is edited via the UI, and the recomputation was getting annoyingly slow, I set up separate params_staging and params_live spreadsheets, with almost all of the shapes defined by formulas in terms of params_live.  You edit the parameters in params_staging and then run an update macro, which copies the parameters to params_live and then triggers a single recomputation.  A second reason the macro is needed is that the design contains a spline (IIRC) and FreeCAD does not support assigning formulas to spline parameters, so the spline parameters are set by the macro.  Place the appropriate macro in your user macro directory, typically ~/.FreeCAD/Macro/:

I approximated the shape of the tip of the Here One earbud as a stack of two elliptical cylinders with aligned axes: the larger one right at the tip is called "stage 2" and the smaller one closer to the body of the earbud is called "stage 1".  The Here One adapter model uses a coordinate system with the origin at the center of the base of stage 1, the positive X axis along the major axis of the ellipse directed toward the top of the ear, and the positive Z axis along the cylindrical axis directed away from the body of the earbud.  Since FreeCAD always uses a right-handed coordinate system, to have coordinates with similar meaning for both ears (which are mirror images to a first approximation), we define a coordinate "out" that equals positive Y for the left ear and negative Y for the right ear; the side parameter in params_staging controls this relationship.  The positive "out" direction is roughly the back of the head.  The adapter base is fixed in this coordinate system.  The most important parameters control the position and orientation of the nozzle in this coordinate system:

In the current Here One adapter, the wide base is simply centered around the earbud tip.  That was the simplest to implement, and my ears happened to be flexible enough that the adapters would fit.  However, it's conceivable that you might need to change the design of the base to get a proper fit.

For the Dash adapter, I approximated the cross section of the earbud tip as circular and made a radially symmetric base.  This means the base can rotate on the earbud tip, though for good noise isolation, it should be tight enough that it doesn't rotate freely.  In that older design, I fixed the projection of the nozzle axis onto the XY-plane to be in the direction of positive X without loss of generality.  Thus, the X axis no longer has a meaning relative to the earbud and there is no nozzle_dir_out parameter, but the other parameters described above have the same meanings in terms of the coordinate system.

I'm not going to take the time to document the rest of the structure of the models now.  In particular, there may be some bug fixes or differences among the model versions above that I have forgotten to describe.  Feel free to send me questions, and I will add the answers to this page as appropriate.

A common problem in editing the models is that changes to parameters change the edge structure of the drilled_body in a way that invalidates the definition of the joint_fillet.  If this happens, the joint_fillet will not update and you'll see a small red error icon on it in the model tree.  To iterate on the parameters, it may be easiest to hide the joint_fillet and just look at the drilled_body.  When you're ready to update the joint_fillet, right-click it and choose "Edit fillet edges".  One or both of the following may have happened:

When you are done changing the settings, click "OK" and see whether the error icon is gone.  If not, you may not have reduced the radius enough or you may have hit a problem I haven't described here.


I recommend making the adapters out of Formlabs Durable Resin, and I recommend the 3D Hubs marketplace for printing services ("hubs").  As of 2018-04-14, I've gotten good results from several hubs, so you can most likely choose any hub that looks good to you.  When I was using Formlabs Tough Resin, I had a lot of trouble with hubs not curing it properly, but this has not been a problem with Formlabs Durable Resin.

You can expect it to take some force to put the adapters on and off the earpieces, but not a huge amount (I don't know how to be more precise).  If it feels like the adapter is still significantly strained after it is all the way on the earpiece, something is probably wrong.  You may tear an adapter if you aren't careful, so be sure to order spares in advance.

The mold

The mold that holds the earbud in the concha can be made with at home with a "make your own earplugs / ear molds" kit: you mix the molding material and press it into your ear, and it hardens into shape.  I recommend the EZ-Form kit from Ear Plug Superstore (generally a good supplier), which is conveniently available in black (really a dark gray) to match the black earbuds.  To make a mold:

  1. Attach the adapter to the earbud.  Set aside a foam tip to use for molding since it may get dirty with molding material; you can reuse it for multiple molds.  Mount this foam tip on the adapter.
  2. If you are using the Dash adapter with the radially symmetric base (which can rotate on the earbud tip), put the assembly in your ear and adjust the rotation of the earbud with respect to the adapter as desired, then remove the assembly from your ear.  (This isn't foolproof since the joint can get bumped to a different rotation later, but I thought it might help.)
  3. Cover the microphone hole(s) on the outer face of the earbud with a piece of tape to keep the molding material out.  For the Here One, where the holes go close to the rim of the outer face, take extra care to seal the tape over all the holes as best you can.  I just cut a square of tape, placed it on the outer face, and trimmed the corners to the circular shape with a pocketknife scissors.  I don't recommend reusing the tape for multiple molds, as it won't seal well enough the second time.  When I did get molding material in the Here One holes, I was able to dig enough of it out with the tip of a push pin that the microphones worked again, at the cost of scratching the plastic.
  4. Mix the molding material according to the directions and spread the blob of material across the inner face of the earbud.  Spread it around the tip of the earbud in both directions and join the ends together.  Spread it along all sides of the earbud to be at least flush with the outer face.
  5. Compress the foam tip as you normally would and maneuver the blob into position in your ear as best you can.  I was afraid that by pressing on the mold, I would form dips that would remain as gaps against my ear, but this ultimately didn't seem to be a problem.
  6. Press the material around the earbud into your concha so it fills the concha snugly.  Especially make sure to fill the area under the ridge at the top of the concha, including the corner under the flap toward the front of your head (see the Here One photos), since this part of the mold (in combination with the foam tip) will help lock the earpiece into your ear in two places.  Avoid shoving the earbud to a different position, as it's hard to fill in the side of the mold where you opened up space and you'll likely end up with a mold that doesn't snugly fill the concha.
  7. Allow the material to set as directed.
  8. Remove the mold from your ear and remove the adapter.  Trim away material that extends outside of the concha and isn't necessary to hold the earbud; I recommend using a pocketknife scissors.  Cut away the material covering the outer face of the earbud so the earbud can be removed from the mold, but leave the earbud in the mold as you continue trimming since it will help the mold keep its shape.  If you are using the Dash (or Headphone), cut a hole in the inner face of the mold for the sensors; for that step, it's easier to remove the earbud.

One EZ-Form kit is good for two molds (so you can make one for each ear), but it may take a few tries to get a good mold, so you may want to buy two or three kits.

I've found the EZ-Form molds quite comfortable.  The one problem I had with this kit is that the material sets really quickly: after about 30 seconds from the start of mixing, it would no longer join permanently when pressed together.  So it's important to work quickly.  As of 2016-10-08, after several weeks of deforming the molds as I put the earbuds in and out, they are starting to tear and I may soon need to make new ones.  I also tried the Radians kit; it had a more reasonable setting time, but the molds came out uncomfortably stiff.


I applied the Silicote coating sold by Ear Plug Superstore to my molds (after the photos on this page were taken).  The coating is slightly tacky and helps the mold stick to the ear all around to further improve the comfort and security of fit.  The product is short on usage instructions.  I just poured a little bit of the liquid into a small plastic container, held each mold with a tweezers, dipped each side into the coating (only the surfaces that touch the ear matter), and left the molds on a paper towel to dry.  I judged the molds dry enough to use after about an hour or so, though they smelled bad for a day or two until the coating was completely dry.

Matt McCutchen's Web SiteMaximum noise isolation for truly wireless earphones  (Top, Introduction, Design overview, Usage, The adapter, The mold, Bottom).  Email me about this page.
Modification time of this page's main source file: 2018-04-15 01:22:38 +0000
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