When I first started learning about custom keyboard construction, I was taken aback by all the different terminology and what they all meant. Even with guides like Deskthority’s Custom Keyboard Construction wiki entry, it was hard for me to get a grasp of everything and understand how that translated into the actual performance of a keyboard.
This, along with ‘gatekeeping’ by elitist collectors and the general lack of understanding about keyboard construction pushed me to write this guide. I want to preface with the fact that people have different preferences for typing feel and sound — some people like flexible plates, some people like very stiff plates, some people like something in between and some people like everything. Also, note that case construction is only one part of the typing feel and sound equation for a keyboard — switches and keycaps are equally important parts.
Hard Plates v. Soft Plates and Vibration Science
The main factor affecting typing feel is how hard the plate is during bottom out. All plates will bend/flex to some extent, but some more than others. From my 2nd year engineering classes, I learned that the amount of deflection/flex is a function of the material’s Young’s Modulus (think stiffness), position of supports (how the plate is mounted) and moment of inertia (think the distribution of the plate’s mass). Thus, all else equal, the lower the Young’s Modulus and moment of inertia, the greater the deflection/flex of the plate.
Understanding the physics behind vibration science is crucial in our discussion about sound production. In general, the denser a keyboard part is, the higher the pitch produced because sound waves travel faster in denser mediums and higher speeds produce higher frequency sounds. Also, the more volume a keyboard part has, the more singular the sound produced as the sound waves have more material to travel through, dampening the sound produced.
In the early days of keyboard group buys, steel and aluminum (with brass a little later on ~2016) were the only options we could choose from. Recently, we’ve seen an uptick in different plate materials like plastics (ABS, acrylic, polycarbonate), carbon fibre and FR4. I’ve also been hearing chatter about titanium, PBT and copper plates being offered. Suffice to say, the plate material is the case element that we’ve seen the most experimentation in.
Understanding the performance aspects of plate materials is relatively straightforward. In order of most stiff to least stiff, the plate materials rank: steel > brass > aluminum > acrylic = polycarbonate > plateless (not to be confused with PCB mount — that refers to the switch bottom). As mentioned in the previous section, the stiffness of the plate is linked to the Young’s Modulus of the material, with steel having the largest Young’s modulus of the common plate materials. While the Young’s Modulus of materials does vary a little based on their alloying, the order of stiffness mentioned is usually accurate.
While it may seem intuitive to min-max a certain plate feel (offer only steel for hard plate setups and only plateless for soft ones), there are many people who prefer aluminum as the perfect middle ground of having flex but still retaining a more metallic, singular bottom out sound.
With that being said, one thing I’d like to see more of in keyboard development is a PCB with mounting tabs for a top-mounted plateless keyboard like the JER-A06. We have seen the opposite end of the stiffness spectrum fully explored with stainless steel sandwich mounted plates, so it’s about time we got some love for the flexy side of things.
In terms of sound profile from bright and singular to deep and reverby, it follows similarly: steel > brass > aluminum > plateless. However, from my experience, brass has a special sound signature to it that is deeper and more musical than both steel and aluminum, which makes it special as a plate material. Not to say that keyboard sound signatures are nearly as significant as trumpet sound signatures, but this is why brass is the material of choice in certain musical instruments.
1.5mm plates have been the standard plate thickness since the old Cherry days of keyboards and has worked well for us all this while. Besides the acrylic custom community in which 5mm (the maximum possible for Cherry) acrylic plates have been around by necessity, plate thickness wasn’t really something that custom keyboard designers intentionally messed with.
In the last year or two, though, boards like ZealPC’s Zephyr and RAMA’s M60-A that use the thicker 5mm plates has sparked a lot of discussion about its viability. Some keyboard enthusiasts have even called 2018 the ‘Year of the 5mm Plate’. That aside, thicker plates are stiffer and have more material for vibrations to travel through, making for a harder bottom out feel and a more high-pitched, singular bottom out sound.
Flex cuts (universal plate, intentional flex cuts, fixed layout)
For the purpose of simplification, plate flex cuts are through cuts made to the plate on top of the minimum needed to put switches in. By this definition, a fixed layout plate has no flex cuts, whereas a universal plate that takes away material from the plate to support multiple layouts does. The more flex cuts a plate has, the smaller amount of material it contains, providing for a more flexible typing feel and a more reverby, deeper bottom out sound.
Aside from layout-bound flex cuts, keyboard designers have intentionally designed plates with additional cuts since the early days of Korean kustom keyboards. Famously, the OTD 360 Corsa (sidenote, but check out this really cool project) had flex cuts all over and around the alpha cluster to promote flex and isolate the alpha cluster from the rest of the keyboard. To my glee, designers like riotonthebay and yuktsi are bringing back the flex cuts with their respective Keycult No.1 and TGR Jane V2 keyboards. The Jane V2’s brass plate-only option defeats the purpose of flex cuts (brass plates are much harder than aluminum), nonetheless I’m glad that designers are not letting this idea die with the old kustoms.
The Plate-Mounting System
Tray-Mounted Plates/Tray Mount
The tray-mounted plate is the most basic and commonly used mounting method of any custom keyboard. Essentially, tray mount keyboards act as a drop-in box with standoffs onto which the PCB/plate combo is secured to. The standard tray mount arrangement originated from replacement cases made for the Poker keyboard back in the day, and has persisted to this day, serving as the bread-and-butter of KBDfans’ custom keyboard business.
For all intents and purposes, this is a perfectly fine way of constraining the PCB to the case. Tray cases are cheap to manufacture but you get the same customizability and modularity as more complicated plate mounting systems. However, because of a mounting post right in the middle of the alpha cluster, there’s a hard spot in between the ‘G’ and ‘H’ keys that makes for a discontinuous typing feel. Custom keyboard makers have fixed this by removing the center post on their tray mounts at the cost of having to use a proprietary PCB. However, as I’ve mentioned in the review of the Duck Raven, a tray mount sans center post, I’d take the far improved typing experience any day.
Top-Mounted Plates/Top Mount
Keyboard cases with top-mounted keyboards generally consists of two main parts: the top case and the bottom case. Top-mounted plates have mounting tabs with screw holes that screw onto the top case, which in turn is screwed onto the bottom case to fully assemble the keyboard. Top-mounting has become the go-to plate mounting system for custom keyboard designers and for good reason. It performs admirably for both hard and soft plate setups, while also being easy to implement as there are many other top mount keyboards to base off.
While I do think top-mounted plates perform very well, it is unhealthy that it has become a default option for most keyboard designers. Top-mounting may very well be the best way to construct keyboards, but we’ll never truly know until we experiment with other plate mounting systems. As such, I hope keyboard designers at least try to innovate in this fundamental part of keyboard construction.
Bottom-Mounted Plates/Bottom Mount
Bottom-mounted plates are similar to top-mounted plates in their use of mounting tabs, but with the tabs mounted to the bottom case instead of the top case. In theory, this should provide for a more singular bottom out sound and a more stable typing experience as bottom cases tend to have more material for vibrations to diffuse through than top cases. How much of an improvement that is, I can’t say for certain. This is because bottom-mounted keyboards are few and far in-between — only the KBD 8X and old KMACs come to mind. So, keyboard designers, try this out and you have my money.
Sandwich-Mounted Plates/Sandwich Mount
Sandwich-mounted plates work exactly how it sounds: the top case and bottom case sandwich the plate between them, and the bottom half is screwed to the top, holding all three pieces together. Because sandwich-mounted plates are constrained continously around the plate instead of at distinct mounting points, they flex less than their top/bottom-mounted counterparts, providing for a harder bottom out. Also, because the plate is connected to both the top and the bottom cases, sandwich-mounted keyboards are better able to dampen bottom-out vibrations, making for a more singular bottom out sound.
More than half of kin25’s TX keyboards use a sandwich mount to excellent results, providing for the hardest plate setups you can buy. As I mentioned in my article on TX keyboards, kin25 wanted the brass sandwich-mounted plates on his flagship TX60 and TX65 keyboards to do exactly that.
Unlike the previous plate mounting systems mentioned, integrated plate setups don’t have a removable PCB/plate combo. This is because the plate and top case are milled out from the same block of material. As a result, similar to how sandwich mounts are constrained, integrated plates are constrained continuously on their perimeters. This provides for a hard bottom out feel like the sandwich, just less so because it’s only constrained on the top side and not on both sides. Integrated plates also tend to be louder and more reverby because they’re usually attached to the lighter top case.
Case design also contributes to sound production (just to a lesser degree) as it directly affects the amount of material vibrations have to diffuse through. All of density of material, elevation angle, height, layout, case thickness, bezels and brass/steel weights contributes to the amount of material in the case. This makes designing a case for a specific sound production very subjective and brings up a lot of questions. What is the minimum amount of material the case needs to sound a certain way? What is the point of diminishing return past which adding more material doesn’t change the sound too much anymore? If we’re really to call ourselves quote-unquote designers, these are the things we need to be thinking about.
One example of a keyboard that is designed to maximize vibration diffusion and a hard bottom out is the TX60/65 keyboard by kin25 (yes, again with the TX shilling). While its layout is relatively compact (compared to TKLs, that is), it is VERY chunky and it has a large brass weight on its underside, making it extremely heavy for its 60%/65% size. It also comes with a sandwich-mounted brass plate adds more heft to the keyboard. You can tell that the TX60/65 is designed for maximum vibration reduction and it shows in the performance of the keyboard.
Aside from vibration reduction, case design also affects how hollow the keyboard sounds. The larger the distance from the PCB to base of the bottom case and the larger the distance from the bottom of the keyboard to the surface the keyboard is on, the more hollow the keyboard will sound.
This can be mitigated to an extent with usage of denser materials all around the case. For example, while the LZ GH V2 has a huge space underneath its case, it still manages to not sound hollow as the entire bottom case is made of super dense brass.
In pursuit of the most singular and quiet bottom out sound possible, keyboard enthusiasts have started adding materials with dampening characteristics to their keyboards. By adding stuff lilke sorbothane sheets, shelf liners and vibration dampening mats, hollow sounding keyboards that are otherwise awesome can become truly awesome. For example, keyboards like the M60-A, CA66 and the HHKB are unique and cool keyboards that fall short because of hollowness, but are greatly improved with dampeners installed. Of course, if keyboards were designed well in the first place, add-on dampeners would not be necessary. But, it’s nice to know that if you get a dud of a keyboard, you’re not just shit outta luck.
Another way keyboard designers have been toying around with dampeners is by using elastic material to cushion the bottom out feel of a keyboard. We’ve seen some of this through the psuedo-gasket mount of the Keycult No.1 and the o-ring cushion on both the Hineybush Compact and Windeh’s Reflex/Paradox. While not new, this adds another design element for designers to consider and that’s awesome.
Integration of Parts
While in the previous sections, case elements were described as distinct features, it is possible for designers to combine them in creative ways. While this complicates the physics of it all and makes it more difficult to anticipate how a keyboard will feel or sound, the move towards experimenting in this regard has been an interesting development in keyboard science this year.
One recent example of a keyboard that combines different case construction elements is Quantrik’s Kyuu keyboard. Instead of just using a single plate-mounting system, the Kyuu’s plate is mounted both by sandwich on the top half and by top mount on the bottom. The plate also shows through the sides and top of the case as a psuedo-midpiece accent ala Lin3x’s Dolphin and EM7 keyboards. This breaks all the rules of plate mounting and I find that fascinating.
The Keycult No.1 is another keyboard that combines multiple construction elements in an interesting way. Instead of having separate pieces for the weight and accented midpiece, designer riotonthebay combined the two elements for a weight/midpiece combo that is milled out of a single block of metal. This makes for one HEFTY keyboard that should diffuse vibrations better than the standard rectangular weighted keyboards.
There is countless opportunities for experimentation here because of the multiple combinations of case elements theoretically possible and I’m excited that we’re trending in this direction.
Keyboard construction is such an important part of the typing feel and sound equation of the keyboard, but yet it is one of the least talked about parts of it. From my experience hanging around Discord servers, talk about keyboard cases usually devolves into just the aesthetics of it (which is terrible compared to real product design by the way, but that’s a topic for another time) instead of the ‘why it performs the way it does’.
What I hope for with this is that the overall understanding of how keyboards work improves in the community, When joining a keyboard group buy, all we get is a mere spec sheet with all of this information that tells us nothing about its performance. We can’t tell how a keyboard is going to type or sound before getting it, but this information can at least help us better guess what we’re getting our $400+ into.
I also hope that keyboard designers take this and actually design their keyboards to go for a certain typing feel/sound instead of just ticking the hottest features of the month off a checklist. I want keyboard designers to actually exhaust all their design options and experiment with everything to distill the ultimate version of their design. Basically, I want them to design a keyboard. Like, Dieter Rams or Jonny Ive-level, 900IQ-type design.
Keyboards are great. They can be better.