Poron case foam warms your keyboard without deadening it
Poron case foam is the cheapest way to warm up a hollow, pingy keyboard. Its open-cell structure soaks up high-pitched ringing and leaves the low thock alone. Too much of it deadens a board, though. Corsair packed over 200g of foam and silicone into the Makr Pro 75 , and KitGuru’s reviewer called the sound dead.
Key Takeaways
- Poron case foam is the cheapest, easiest way to warm a keyboard’s sound.
- Too much foam kills the sound you wanted.
- Case foam does the most, plate foam fine-tunes, PCB foam stops ping.
- Poron cuts the high ping and keeps the deep thock.
- Corsair’s Makr Pro 75 packed in 200g of foam and sounded dead.
What do case, plate, and PCB foam do?
A keyboard can take foam in three places, and Glacier’s layer-by-layer guide to keyboard foam gives each one a different job.
- Case foam sits in the bottom of the case and fills the empty air cavity. Glacier calls it the big cavity tuner, because it cuts the hollow echo and shapes the overall sound more than any other layer.
- Plate foam sits between the plate and the switches, where it softens the attack of each press and smooths harsh overtones. It also keeps the plate from shaking against the case.
- PCB foam is pocketed right under the circuit board. It stops a thin or flexible board from acting like a drumhead, which is where much of the metallic ping comes from.
Aluminium plates ring bright where FR4 stays neutral , so an aluminium plate needs plate foam more than a softer FR4 plate does.
How foam changes keyboard sound
Every keypress sends a small burst of energy from the switch through the plate and circuit board into the case. Hard surfaces and empty cavities bounce that energy back as echo and high-pitched ping, and some of it lingers as sustain.
Foam turns part of that vibration into a tiny amount of heat through friction, so less of it returns as sound. Glacier lists the audible results as shorter sustain, fewer sharp high-frequency peaks, and a tonal balance that tilts toward the low end. That low tilt is what builders mean when they call a board warm or thocky.
Where the foam goes and how thick it is count for more than how much you stuff in. A layer that soaks up the highs warms the board. One that also soaks up the lows takes the thock away along with the ping.
Why Poron case foam is the pick for warm thock
Case foam can warm a board or kill it depending on the material, and Glacier’s guide sorts the common options like this:
| Material | Firmness | What it does to the sound |
|---|---|---|
| EVA | Medium | Cheap baseline damping, a safe starting point |
| Neoprene | Firm | Cuts the highs well and lasts, but feels harder |
| Felt | Soft | Warmer, more muffled thock, used mostly as plate foam |
| Poron | Open-cell, compressible | Trims high-frequency peaks and keeps the thock |
Poron is the only option on that list that targets the ping and leaves the thock. It’s an open-cell polyurethane made by Rogers Corporation. Rogers says its PORON foam resists collapsing under long-term pressure while still damping vibration. The damping eats the ping, and the resistance to collapse means a sheet squeezed under a PCB keeps its thickness.
Rogers also says it’s the only maker of PORON and that the name shouldn’t be used for generic polyurethane foam. A cheap sheet labelled Poron may not be the Rogers product at all.
Ready-cut modding sheets are cheap and easy to find:
- Kinetic Labs Poron case foam comes in 2mm or 3mm for $9.99.
- Thock King’s PORON sheet measures 17 by 5 inches, in 2mm or 3mm, for $7.95.
- SerpentKeys Poron case foam measures 40 by 13 cm, with perforated lines for 60%, 65% and TKL boards, from £5.75.
Start with the 2mm sheet. You can always add a second layer later, but a board that sounds dead only comes back when you pull the foam out again.
The layering recipes for warm, muted, or balanced sound
Glacier’s guide groups foam builds into three recipes.
| Goal | Plate foam | PCB foam | Case foam | Expected result |
|---|---|---|---|---|
| Warm thock (most popular) | Thin | Poron | Medium | Keeps the attack, cuts harsh highs, adds body |
| Muted and quiet | Thick | Firm | Thick | Good for offices, can go too dead |
| Balanced | Thin foam or felt only | None | Light | Keeps clarity, smooths peaks |
Only the muted build uses thick case foam, so warmth comes from a medium case layer and a Poron PCB layer working together.
Mount type changes how much foam a board can take. Gasket-mounted boards already isolate some vibration through their soft mounts, so Glacier suggests lighter foam to keep the mount’s bounce. Tray-mounted boards screw the PCB straight to the case and can usually take more foam before they lose their feel.
Glacier’s advice is to start conservative and stack layers only when you still hear echo. No source publishes a gram or millimetre target for a given board size, so you set the thickness by ear.
When foam goes too far, the 200g Makr Pro warning
KitGuru’s Carlos Ribeiro reviewed the Makr Pro 75, a Corsair board with a CNC aluminium case and Hall effect switches.
Corsair’s decision to pack the case with over 200g of foam and silicone results in a “dead” sound profile that removes all character from the sound.
He listed the over-dampened sound among the cons of a board that sells for £219.99 in the UK.
Tom’s Hardware’s review counted eight layers of sound dampening in the same case. Sarah Jacobsson Purewal found the sound decent, bright and crisp, and credited the tone to Corsair’s rigid FR4 plate. She added that she prefers something deeper and louder, and that an enthusiast board with similar features will sound better for less money. Eight layers made the Makr Pro quieter without giving it the body people call thock.
How to foam a keyboard for warm thock without deadening it
Set your sound goal
Decide up front whether you want warm thock, a quiet muted board, or a balanced sound. The goal picks your materials and how thick you go.
Cut and fit case foam first
Trace the case cavity onto the foam and mark the standoffs and screw posts you need to avoid. Cut medium Poron with a sharp knife and a straight edge, then dry-fit it. Reassemble and listen to it alone before adding more. Hold it with removable double-sided tape while you experiment, because adhesive-backed foam is much harder to take back out.
Add thin plate foam
Cut a precise hole for each switch and keep the layer thin. Leave the stabilizer areas clear so the foam doesn’t compress them and make those keys feel mushy. Then reassemble and listen for a softer attack.
Add Poron PCB foam last
Pocket a thin Poron sheet under the PCB, cutting around solder joints, connectors and screw posts. This layer kills ping without changing how the keys feel.
Test and compare
Record a short clip before and after each layer, with the microphone in the same spot and the same room. Listen for attack, sustain, ping and thock. If the board starts to sound lifeless, the last layer you added went too far, so thin it or take it out.