We’ve covered everything from the basics of custom mechanical keyboards to building from scratch. After you’ve built your own mechanical keyboard, modifying it to perfection is the next evolutionary step. We took care of this with the stabilizer and switch modification guide. This brings us to the last part of the keyboard modification series where we improve the keyboard case and plate. Be sure to read these articles to understand the terminology and basic concepts used in this guide.
Keyboards are percussion instruments
As with stabilizers and switches, buying high-quality CNC machined aluminum or brass housings doesn’t stand out from the crowd. Keyboard cases are mostly hollow, but combine that with the click of the keys, and you have a percussion instrument on your hands. No wonder fans of custom mechanical keyboards are quite particular about their sound.
This is all the more important for expensive keyboards with CNC milled metal cases. These tend to have a higher pitch due to the nature of the material, making them tiny and hollow without proper acoustic treatment. This guide intends to deal with it, that is to say acoustically attenuate the case as well as the plate to improve the sound of your keyboard.
What you need to get started
This keyboard modification guide is quite simple. Disassembling and assembling custom mechanical keyboards is quite simple. All you need for this mod is good soundproofing materials, sharp cutting tools and precise measuring instruments. The list of tools required is not long, but I have included some optional tools that are more precise and / or make the task easier.
1. Sound absorbing material
This comes in different forms. The one used in this guide is Ethylene vinyl acetate foam, which is inexpensive and easily accessible at craft stores. Buy at least a few keyboard-size sheets in thicknesses of 1 mm and 2 mm. This will allow you to combine them to get the correct thickness. If you are willing to spend more, you can get better results with rubber sheets. If your pockets are deep, you can try an alternative made in the USA called Sorbothane. It is used by NASA, so expect it to work best. However, it can very expensive for what we intend to do in this guide.
2. Sharp cutting tools
The best tool for the job is a craft / hobby knife from a reputable brand like Xacto. The sharper the blade, the faster and cleaner your work will be. Box cutters work in a pinch, but they are relatively dull and unwieldy for the type of fine cut needed here.
3. Measuring instruments
While the humble ruler works for two-dimensional measurements, taking internal measurements of complex 3D objects such as a keyboard case requires something more complex, like digital or dial calipers. A tape measure also works if necessary. Making measurement marks on a thin strip of paper is a convenient way to measure the dimensions of complex 3D objects. Simply lay the strip of paper flat when you have finished marking and measure the markings with an ordinary ruler.
Acoustic damping of the plate
Much of the hollow, oily note on a keyboard comes from the metal plate that vibrates with the keys. This is further amplified by the 3.5mm gap between the PCB and the plate acting as an acoustic chamber. We will fill this space with a damping material to reduce the hollow sound. The anti-vibration properties of the material also prevent the plate from generating noise. This should allow the natural sound of the switch to stand out without being overshadowed by the noise of the plate.
1. It may sound counterintuitive, but we start by measuring the dimensions of the case instead of the plate. This applies to all types of enclosure mounting styles, from tray mounting to sandwich mounting, as our goal is to have the acoustic damping material (EVA foam in this case) to protrude beyond the plate to create an airtight seal with the housing. This will significantly reduce internal noise from leaks outside the housing.
The foam conforms, so you can use exact dimensions if you are using precise measuring instruments, or you can add one millimeter to each dimension. It is better to have more material and trim later than not to succeed.
2. Transfer the measurements to the EVA foam sheet.
The gap between the plate and the foam is 3.5 mm on all keyboards. EVA foam is generally found in sizes 1 mm, 2 mm, 3 mm and 5 mm. You will therefore need to use two 2mm sheets or a combination of 3mm and 1mm sheets. The additional thickness of 0.5 mm improves damping. Use double-sided tape or foam-compatible glue to hold the sheets together. This is important to avoid headaches when cutting the sheet.
3. Use the plate as a stencil to transfer the cut lines to the EVA foam. Your cuts will be more precise if you use a fine marking tool and keep the cutting lines closer to the edges of the plate.
4. Use a DIY / craft knife to make all the cuts. Thinner cuts, such as the holes for the switches, will come out clean and precise if you use a sharp blade. Using a dull blade will make your job longer, frustrating and inaccurate.
Tray-mounted keyboards will need an appropriately sized hole punch to create space for the tray-mounted screw studs. You can also cut holes with a blade, but the result is neither as tidy nor as precise as using a dedicated punching tool.
5. Depending on the physical dimensions of your preferred type of stabilizer, you may or may not have to cut certain materials to fit them.
6. Finalize the PCB / plate assembly by soldering the switches to the PCB. See our switch replacement guide for how to solder the switches.
Don’t forget the case
The acoustic treatment of the housing is much less complicated and tedious than the plate. The interior lining of a box with foam is not complicated, but it is very important. CNC milled metal cases are very dense supports that transfer internal noise quite efficiently. Adding a sound absorbing layer prevents this from happening. The actual method will vary very slightly depending on the mounting style of your case. Be sure to read our basic guide on the keyboard if it sounded Greek and Latin to you. This article covers all the basics.
1. The first step is to determine the space between the housing floor and the PCB to determine the thickness of the EVA foam sheet. For tray mounting boxes, this involves measuring the height of the PCB mounting posts and deducting the height of the tallest component that projects from the bottom of the PCB. In the example below, the PCB is mounted at a height of 3.2mm, and the tallest component under the PCB is a shade greater than 1mm, so we can use 2mm foam.
Calculations are even easier for all other types of housing mounting styles. You just need to measure the distance between the bottom of the plate and the bottom of the case. Then subtract it with the obligatory gap of 3.5 mm between the plate and the PCB in addition to the thickness of the PCB and the highest component which projects from it. For example, if the distance between the bottom of the plate and the bottom of the case is 10 mm, the PCB has a thickness of 2 mm and the highest component on the bottom has a height of 1.5 mm, you can use 10 – (3.5 + 2 + 1.5) = 3 mm thick EVA foam sheet.
2. We have already measured the dimensions of the housing, so it only remains to cut the EVA foam inserts to the appropriate dimensions. Tray mounting boxes require pre-drilled holes for mounting posts. Additional cutouts for the USB port should also be measured, marked and cut as shown below.
3. If your case has hollow sections, measure the depth and fill it with an EVA foam cutout with the appropriate dimensions.
4. With the floor of the case treated acoustically, we move on the four vertical sides. Remember the distance from the bottom of the plate to the bottom of the case that you measured earlier? This is the extent of the EVA foam strip you will need to cover the sides of the case. The thickness of this strip of foam must be at least 1 mm for effective damping and must not exceed 2 mm, otherwise the PCB will catch on it.
Top / bottom, seal, and sandwich-mount enclosures will require spaces in this strip, as shown below. Spaces are necessary to avoid clearance issues with mounting posts.
That’s all we can say about it. Assemble your keyboard and marvel at how radically improved it looks.
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