A project of developing my own modular headphones [DIY, 3D printed]

Discussion in 'DIY' started by Tomislav_L, Jun 21, 2020.

  1. Tomislav_L

    Tomislav_L Rando

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    Hello everyone,

    I've been working on a DIY project of designing and building my own headphones for quite a while now, and I'm at a point where I feel like I have some interesting material to share, maybe get some feedback, opinions, criticism, etc., and maybe even have other members of the community get involved. The project is not finished, it's still evolving, but it's kinda grown way past the size and depth that I've originally planned for it. I hope you'll like it and have as much fun exploring it as I've had working on it, and I hope the material I'll share will at least partially show how much passion is behind the project, as that's what DIY is all about.


    DIY headphone project:

    I won't spend a lot of time talking about the project background, because I'll talk about that and more about the project itself in more detail separately if there will be an interest for it, but it's something I've been working on for more than three years at this point, completely alone, in my free time while not busy in medical school. So, I'm not a part of some company or some big team of people, I'm just a single guy with a lot of passion for headphones, with quite a lot of previous experience with headphones (owned multiple flagships, tested a bunch of them, written reviews, etc.), and with a crazy goal of designing and building my own headphones in exactly the ways that I want, lucky to be living in times where modern technologies actually enable me to invest creative energy into this hobby and end up with something real. It also helped me to kinda run away from the daily university routines, and it's been sort of a transition from drawing/sketching style of design that I've been into since I can remember, to a more 3D/CAD style combined with 3D printing. So please take that into consideration, as everything in this project has been done "on the side", with a very limited budget, and by teaching myself how to do things from scratch as I went along, so not everything about it will be perfect, although that's something I strive for.

    I've designed multiple headphones during this project as a part of the learning process, but I'll present three models for now, or their "proof-of-concept" prototypes. Over the period of these couple of years, I've invested over 2000 hours into the project itself, so it's quite big at this point with a lot of depth and aspects to it on top of just the headphones, including detailed testing of state-of-the-art additive manufacturing technologies and materials, post-processing raw printed parts to look great, etc. I have a lot of material I can present or talk about regarding those topics, if there will be interest for it. I think the most interesting part will be the concept of modular headphone platforms that I've spent most of the time working on. Two of the models I'll eventually present are entirely built around the concept of a modular headphone platform, with all of their parts individually replaceable, suited for use with multiple drivers and with various sound tuning options possible.

    [​IMG]

    You can see the render of these three headphones side by side, obviously just a virtual representation of how I'd want them to look one day, the prototypes look a little different because of different materials, but they are based on these actual designs, meaning these renders are of actual solid, fully designed headphone assemblies with actual functioning parts, they're not just pictures. :)



    V1 PROTOTYPE

    For now, I'll show the V1 model in more detail, yea I know, it's a very boring name. :)

    [​IMG]

    I also don't want to post too many large images here to clog up the thread, so I uploaded them to imgur instead, as public galleries that you can check out if you want. My signatures are watermarked on the pictures because they're all public, but if you want a specific picture raw for whatever reason, let me know.

    V1 4K render gallery

    V1 prototype v.1.0 (silver)

    V1 prototype v.1.0 (black)



    About the headphone:

    The V1 headphone is my take on the Grado-like DIY headphones, and is the simplest of the three separate headphone models that I'll show. As you know, it's a very popular type of headphone in the DIY community, and there are a lot of drivers and ear pads on the market designed specifically for them, so they are quite fuss-free to build, which is one of the reasons I've decided to work on this model in the first place. However, I didn't want to go down the usual route of making wooden ear cups, or sticking with the standard design approach. I've decided to do something different, not just for the sake of making it different, but to offer me more possibilities with a more modern design, and to change certain things I didn't like about that style of headphone. The design is simple and I think quite elegant, with a nicely curved and angled cup that transitions into a chamfer around the grill through two soft edges. The grill sits 3 mm deep below the outer edge of the cup, and is concave in shape, so it gives a nice appearance of depth to the cup, which doesn't quite come across fully on the pictures. I believe it's quite a pretty headphone, but that's obviously subjective. There are no fasteners visible on the cups, no assembly clues, and the individual parts fit together very precisely with no gaps between them, giving the headphone a very smooth feel, while still leaving me some room for customization through use of various materials and finishes. Below the surface the headphone is more complex, and features a modular construction. It can be an on-ear headphone, or a full-sized around-ear headphone, depending on the ear pads used. When it comes to ear pads, I've kept the way of attaching them identical to other similar headphones, meaning that all ear pads on the market that fit on any Grado, or Grado-like headphone out there, fit onto the V1. That is not to say that a different attachment mechanism couldn't be easily designed if there was ever a need for it, or if I ever try to make my own ear pads, which I didn't yet. As for the drivers, the standard 46 mm diameter cutout on the baffle will accept any Grado-mod driver out there from famous brands like Elleven Acoustica, Symphones or Nhoord, but will also fit smaller diameter drivers with a special adapter.



    Design and feature highlights:

    This headphone features certain unique solutions for a headphone of this type:

    Entirely modular
    – Every single part of the headphone is individually removable, in a completely reversible way, specifically designed to be easy to work on and to give me room for customization, which should be the whole point of a DIY headphone. For example, I can easily replace the grill for a different one, either because of sound tuning or aesthetics, or both. The cup itself has been designed with a removable outer shell, which is the part that's painted, and can obviously be used to customize the look of the headphone. The entire rear part of the cup assembly can be removed from the driver baffle without removing the driver or even unplugging the cable, for easy access to the rear acoustic chamber and playing with acoustic treatment options. At the same time, because the tolerances between parts are so small (<0.05mm) and everything fits together incredibly precisely and tightly, once the parts are assembled, the cups feel rock solid. Monolithic is the term that could be used, I guess, since the whole thing feels like it's a single solid piece, and not multiple pieces assembled together. This is something I've worked really hard on and have spent a lot of time playing with various prototype parts.

    Angled drivers
    – It might sound weird to put the drivers at an angle on a headphone like this, but it actually has two benefits. First, it makes the driver slightly more parallel with the angled ear, instead of the rear part of the driver being closer to the ear than the front because of how the L-cusion ear pads sit on the ears, which is positive in terms of sound, and second, it leaves a bit more space for the earlobes when using L-cushion ear pads, so the drivers press on the ears less. Anyone who's ever tried Grado's with L-cushions has probably experienced that uncomfortable feeling of the hard driver cover squeezing their earlobe. I've designed several baffles with various driver angles/forward offsets. The ones seen here are angled at 5 deg (silver headphone) and 2.5 deg (black headphone). The angled drivers also led to an overall angled internal cup design, with the entire rear acoustic chamber being at an angle. This complicated the design, but on top of already mentioned advantages, it also led to certain structural benefits, making the fit between the baffle and the rear part of the cup much tighter. I can explain how and why if someone asks.

    Removable drivers
    – Instead of going for an approach of permanently gluing the drivers into the baffles, or press fitting them in so tightly they're almost impossible to pull out again, I've decided to go for an approach of a combination of a pretty tight fit (but not overly), combined with 6 small screws that can additionally hold the driver in place. This way the driver is securely held in the baffle, but I can still easily remove it if I have to. It also allows me to adjust the driver-to-ear distance by using printed spacer rings which can be put under the driver and basically control how deep in the cutout it sits. Also, it means that a single baffle is compatible with all Grado-mod drivers, since some of them are thicker than others. Each just needs a specific spacer ring. Obviously, smaller diameter drivers would fit as well, with specific adapters.

    Hidden hinge yoke mechanism
    – The yoke is tightly integrated inside of the cup, with 12 degrees of rotation around a horizontal axis, and 360 degrees of rotation around a vertical axis, while nothing is visible on the outside of the cup, except the headband slider being connected to the cup. The issue I've always had with Grado's is that they have a very limited range of cup rotation around the horizontal axis, since the yoke itself sort of presses into the ear pads and can't rotate towards the head. That always led to the ear pads pressing the tops of my ears very hard, which is especially painful in combination with glasses. So that's something I absolutely wanted to avoid and fix. With the increased range of rotation around the horizonal axis, that issue is completely gone on the V1.

    Different headband adjustment mechanism
    - Lastly, the entire geometry of the headband size adjustment and the relation of that to how the cups sit on the ears has been revised compared to similar headphones. I'm using a Beyerdynamic pro headband spring steel, which is IMHO one of the best on the market in terms of evenly distributing the force, and has an ideal amount of clamping force for what I wanted. As you can see the sliders are not straight, they're curved at a very specific radius, their initial angle relative to the headband spring is different than on Grado-like headbands, and the connection of the slider to the yoke is at a slight angle as well. I've experimented with these variables A LOT in order to ensure that the clamping force would be as even as possible at all headband adjustment positions, and to make sure there was enough horizontal cup rotation available in each position, so that the yoke is always sort of in the middle position as far the range of rotation goes, giving the cup some "wiggle room" to rotate and sit on the ears comfortably. Essentially, all these aspects are making the headphone more comfortable and stable on the head, without a clamping force as strong as it's typical for similar headphones, and with the forces on the scalp and the ears distributed more evenly. I can wear these headphones for hours, with original L-cushion ear pads, and not feel any discomfort on my ears or my scalp.



    How it was made:

    All of the parts for these prototypes have been produced with HP Multi-Jet Fusion machines, out of a PA12 plastic material. This state-of-the-art industrial additive manufacturing technology is highlighted by incredible dimensional accuracy, virtually no design rules, and the ability to produce very complex parts, very quickly, ready for use straight out of the machine. Note that comparisons to the more common FDM 3D printing are pointless, as this method is entirely different, with MJF being vastly superior in every regard, sometimes even in terms of cost of use. The entire technology has been developed specifically for engineering purposes and is mostly used in automotive, aerospace, motorsport and similar industries, with the machines costing between $100k and $300k.

    The material itself is an extremely strong, rigid, durable, wear-resistant and chemically-resistant type of plastic meant specifically for highly demanding engineering purposes. Also, it has great elongation at break properties, and it's really impact resistant. It also has great vibration-damping properties. In many ways, it's an ideal material for headphone parts, and quite superior to other plastic materials such as ABS, which is usually used for headphones due to being very cheap. In the future, I will make some parts of these headphones out of Carbon fiber reinforced PA (as I've done for other headphone prototypes in the past), using Selective Laser Sintering technology, and might even experiment with CNC machining aluminium parts, which would make the headphones look like on the renders.

    The general philosophy of designing the cups was to make them as rigid and acoustically inert as possible, and these materials are ideal for it when combined with complex part designs, with a lot of bracing, supporting structures, etc. I didn't want to use wood to make the ear cups for multiple reasons that I'm not gonna get into now, but simply put, there are just too many design limitations and drawbacks when using wood, with only questionable benefits.

    Some of the headphone parts are raw, without any post-processing, and have a very fine and pleasant texture on the surface, while others have been post-processed by me, all done by hand, including hand-polishing up to a highly glossy finish. I've had to experiment with post-processing quite a lot and basically teach myself all about it from scratch, as when I started doing this, there was absolutely no sources on how to post-process SLS or MJF printed parts. It took a lot of time and testing to develop a method that allows me to achieve a perfect finish, but I've managed it. I've even written and filmed a detailed guide on how to do it, in order to help others in case they'll make parts out of these materials.

    [​IMG]

    I'm using original Hirose HR10A series connectors for the detachable cable, while the cable itself is a Sommercable Peacock MkII (same as used originally on Beyerdynamic T1's), with a Neutrik NP3X-B 6.35mm jack. All the fasteners and attachment accessories, including the brass threaded inserts, are Swiss-made by Bossard.



    Tuning options:

    The sound of this headphone largely depends on three aspects. The driver used with it, the ear pads used, and the dimensions/openness of the rear acoustic chamber. For that reason, it's a pretty simple headphone to work with and it's very easy to make it sound really good. Even just putting a good driver into the baffle, without any additional acoustic treatments, results in a very good sound. However, there are several tuning options available to play with:

    • The diameter of the rear acoustic chamber can be modified with 3D printed inserts pressed into the cup, or by attaching certain materials of various degrees of thickness onto the walls.
    • The openness of the grill can be modified by changing the design of the grill itself, or by using acoustic filters / stainless steel mesh / fabrics under the grill, and reducing its transparency to a certain degree.
    • The reflective/absorbtive properties of the acoustic chamber walls can be manipulated by attaching foams or felts onto the walls, or by printing inserts with various irregular patterns and textures designed onto them.
    • Controlling the volume itself, primarily the standing waves behind the driver, can be done by partially filling up the chamber with foam or fibrous polyester materials, such as polyfill, which is specifically designed for that purpose when used in speaker cabinets.
    • Finally, the driver itself can be moved closer or further away from the ear by using driver spacer rings of various thicknesses.
    So, there are plenty of options I can play around with and improve/change the sound of the basic configuration, and two examples of them will be presented in the next section.



    Performance:


    After many iterations of V1 parts since 2018 when I've started developing it, and a lot of experimenting with design variables through multiple prototyping cycles, I've arrived at what I'd consider a finalized version of the headphone design. Not necessarily the last one, as I'm always finding ways to improve the design, but it's now well polished in terms of the assembly process, the fit and finish of the parts, the way the build feels, and I'm more than happy with the way it performs.

    I'll show two headphones here, one finished in metallic silver and the other in metallic black. They're 95% identical in terms of part designs, the only major difference being the fact that the silver version features drivers angled at 5 degrees, while the black version has them angled at 2.5 degrees. In addition to that, the black version has a dual-layer grill design, that secures the acoustic filters in place better than the previous version, and it features a different type of acoustic treatment in the cup itself. All of these variables are minor, and both versions of the headphone perform very similarly, but with some noticeable differences nonetheless.

    I'm gonna try to describe the sound of these headphones while being as unbiased as possible. After years of owning or testing a huge amount of headphones, and writting quite a few reviews, I think I can manage it. On top of that, I'm a huge critic of my own work, and if I didn't really like something, I wouldn't have revealed it, but instead worked on it more to fix it or improve it. Trust me, there's a reason why I have whole boxes full of old "failed" prototype parts. ;)

    First about the similarities between the two builds, as both of them are the V1 model after all. They both feature the same driver, the Elleven Acoustica P1. Why? Of all the Grado-mod aftermarket drivers I've tried, I like this one the most, and it's objectively simply an amazing driver, with a great ability to function equally well in various types of headphones, not just Grado-like builds, which is a huge added bonus. They're expensive at almost $200 a pair, but more than worth it in my opinion. That's not to say other Elleven Acoustica models, or Nhoords, Symphones, etc. aren't great, they're all excellent aftermarket driver, but P1's are my personal favorites. When it comes to ear pads, I like the sound of this driver best when combined with original L-cushions, and that's how I primarily use them, and how they we've been tuned and measured.

    It's really hard to describe the sound of this headphone in any other way than saying it sounds very balanced and smooth, from top to bottom, with a little extra sweetness in the mids and sparkle in the highs. People who've used the P1 driver probably know what I'm talking about.
    This configuration has a very focused, tight, fast and highly detailed sound, but with wonderfully sweet and full mids, one the best I've heard from a dynamic headphone. Not just in terms of how full they are, but in terms of how natural and transparent they are. The "shouty" character typical for similar headphones is almost non-existent too, especially on the black version of the headphone with its acoustic treatment. Mids are without a doubt the highlight of this model in terms of sound, and for that reason it's simply brilliant when it comes to vocal and instrumental music. I've used the Beyerdynamic T1's for many years as a reference headphone, but I'd absolutely never pick them over the V1's for any music that focuses on real instruments or voices. In addition to that, the overall sound resolution of the P1 driver is very, very high, absolutely comparable with drivers in most <$1000 dynamic headphones, and some above that too.

    The low end is very quick, clean and tight, with a great "texture" and a better extension than is typically the case with this type of headphone. It's still not an LCD3 or a TH900, but it's definitely not a typical Grado either, because it doesn't have that massive mid-upper bass peak and a sudden roll off at the bottom. This is a bass response that's very even, without an obvious peak or a "one tone" quality, and with an extension that matches most full-sized open-back dynamic headphones with ease, only starting to roll below 1kHz SPL level at about 50-60 Hz. Even below 40 Hz, there's still plenty of well controlled "rumble" present when needed. Using Chesky's "The ultimate demonstration disc" bass resonance track is a really nice showcase of it. That track can sound boomy and uncontrolled with a lot of headphones, but it's super clean here.

    Higher frequencies are slightly accentuated, but nowhere near the point of making the headphone feel bright in terms of balance. Instead, they provide a great sense of clarity and air in the sound, without being aggressive. This can be further fine tuned with the use of various acoustic foams and fabrics in front of the driver. When leaving the driver uncovered, or with just a transparent dust filter, there's a lot of detail throughout the frequency range. I'm not gonna use the "I can hear things I haven't heard before" cliche, because I've heard or owned plenty of high-end headphones, but this is one of those that makes you notice micro-details and fine nuances in music that most headphones mask or don't make nearly as apparent, and I can tell that with confidence because I've been using a certain selection of reference testing tracks for years, and know exactly how they sound with various headphones. At the same time, it's not a headphone that pushes details forward and tries to be overly analytical, and it's not as aggressive or rough in its presentation as the original Grado's are. It makes music involving and fun to listen to, but in a more refined way. It's more of a velvety smooth saxophone than a loud and distorted electric guitar, and that's all thanks to that sweet mid-range. This might actually be the most impressive thing about it, because sometimes headphones with this level of detail, clarity and speed tend to be overly analytical, aggressive or cold, but the V1 with the P1 driver manages to avoid that quite successfully.

    As with all high resolution headphones, a high quality source is a must in order to fully explore what it's capable of, poorly recorded music will have all its flaws exposed, and it's definitely one of those headphones that makes me avoid certain recordings, while really shining with others. On the other hand, they're actually very easy to power, and even just plugging them into a smartphone makes them sound pretty good and with plenty of volume reserve.

    The sound stage with L-cushions is medium in size, but offers good imaging and great separation. Using the P1 drivers in combination with the G-cushion ear pads results in a slightly higher level of comfort and a slightly more distant and laid back sound, with a bigger sound stage and a greater sense of openness in the sound. That being said, I'm not a big fan of that combination, and don't think the benefit of a bigger sound stage is worth sacrificing the rest of the sound for. Primarily, the bass rolls off too much, with a single big peak at about 120 Hz, and the highs become a bit too aggressive. There are drivers on the market specifically designed for use with the bigger ear pads, and these aren't one of them, so I personally prefer the sound with L-cushions.



    Silver version:

    [​IMG]


    When it comes to specifics of the silver V1 build, other than the obvious visuals, this build sort of represents the most basic configuration possible. In terms of acoustic treatment, it only features a 2mm thick EVA foam padding on the walls of the acoustic chamber, and a perfectly transparent stainless steel mesh under the grill, which has no effect on the sound at all. Essentially, it's as raw as the V1 can get with these drivers.

    [​IMG]

    As can be seen, the silver LTA V1 prototype has a pretty smooth frequency response without major peaks or dips. The area from 50 to 2000 Hz is particularly flat, and manually going through frequencies using a tone generator confirms that.

    Note that I'm using the DT770's only as a reference to show how my measurement rig works. I'm not using them as a performance benchmark.


     
  2. Tomislav_L

    Tomislav_L Rando

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    Black version:

    [​IMG]


    It has slightly updated parts, with very minor design changes, just an added second grill on the rear opening of the ear cup that helps keep the filters or metal mesh sandwiched in place under the main, outer grill. It adds nothing to the transparency of the overall opening, as the inner grill design is perfectly aligned with the outer grill.

    More importantly, this configuration features more advanced acoustic treatment than the silver one. The internal walls of the rear cup chamber are lined with a layer of "dynamat", and then a layer of 3 mm thick acoustic polyester felt on top of it. This makes the cup more inert, and reduces the reflections off of the internal walls. In addition to that, this configuration features something I've been experimenting with for a while, and that is combining 3D printed parts with liquid glass, a special type of epoxy resin used to fill in the cutouts in the components. The reason for doing this is the fact that this resin is extremely rigid and inert, far more than any plastic material, while being only slightly heavier than plastic at the same time. This means that printing components with cutouts, and then filling them in with epoxy resin, leads to more rigid and inert components than they would have been if they were to be printed without cutouts to begin with. The amount of resin used leads to different effects, so in a way, this method can be used to control the resonant properties of plastic parts. The improvements in rigidity will be even more noticeable when I make the raw components themselves out of superior materials such as the Carbon Fiber reinforced Polyamide, which might put them on this level of performance even before filling them with epoxy resin. Another change compared to the previously shown configuration is the mesh used under the grill, which is not a stainless steel mesh, but a SAATI polyester acoustic filter, slightly more transparent than the stainless steel mesh.

    [​IMG]
    Cutouts filled with liquid glass

    In terms of performance, this configuration is a noticeable improvement over the previous one subjectively speaking, not by a large margin, but still definitely an improvement. The acoustic treatment of the rear chamber has led to a slightly more even frequency response, with a 2 kHz peak slightly reduced, and an overall smoother sound, particularly in the high frequencies. On the other hand, the additional rigidity and mass of the components due to the epoxy resin has led to an even tighter bass response.

    Below, the frequency response can be seen again in a direct comparison to the DT770, without any smoothing applied, obviously no EQ, 1/24 oct setting in ARTA, giving the most detailed and raw graphs possible.

    [​IMG]

    CSD Waterfall plot can be seen below, although this measurement is questionable when done on a primitive measurement rig such as mine.

    [​IMG]

    Below, I've added a collection of three measurements with an identical headphone, without being removed from the measurement rig. The only difference is the adjustment of the headband size, leading to slightly tighter and stronger clamping force with each reduction in size. Green line is the lightest clamping force, red the strongest.

    [​IMG]

    In any case, the measurements shown here are the "worst-case-scenario" ones, because of all the possible materials that I could have used to make the parts out of, the most affordable ones have been used to produce these prototypes. On top of that, I can still explore additional acoustic treatment options. Despite that, subjectively speaking I believe the headphones perform very well and I'm definitely happy with their performance/cost ratio, at least if we ignore the costs of actual prototyping and developing, I'm just talking about how much it cost me to put a single prototype together, which is around $600 in this configuration. Obviously, I could have saved some money by not using original Hirose connectors (which alone cost $50) or using cheaper fasteners, primers/fillers/paints/clear coats, etc.


    Future plans:

    The final goal, as with other models I've designed, is to build them in a top configuration, featuring the most advanced Carbon Fiber reinforced Polyamide on functional components, in a combination with CNC machined Aluminium structural and mechanical parts. Several renderings of such headphones can be seen in the render gallery, in various combinations of materials and finishes.



    So much for the V1 model for now. Please if you have questions, ask, anything related to the project or the headphones, the way they were made, painted, tuned, etc.

    Sorry for quite a lengthy post, and I hope it's been interesting. :)
     
  3. Tomislav_L

    Tomislav_L Rando

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    Reserved reply for other models:

    These are headphones I'll write about in more detail separately, but here I'll just leave a few pictures as teasers. ;)

    Both of these headphones are fully modular and can do some things that I think will be very interesting to the modding and DIY communities, mainly the ability to work with various drivers by offering multiple ways to adapt the basic headphone design to suit each individual driver, while also offering ways to tune the sound of each headphone configuration in order to achieve a certain sound signature. It's something I've spent a lot of time developing and making sure it would work in practice, instead of just staying a neat sounding idea on paper. I'll try to come out with more information about them as soon as possible.(next couple of days)

    V2 Prototype

    [​IMG]

    [​IMG]

    [​IMG]


    V3 Prototype

    [​IMG]

    [​IMG]
     

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