is foam in a keyboard good?

Photos taken in house by alex

Ah, foam. The perennial topic. Not only is foam a common topic to discuss, the discussions are often the same: “It ruins a keyboard!” with the common reply “No, it doesn’t!”

Before I get too far into this, I want to make one thing clear: If your opinion is that foam is bad and you use that opinion to insult others who want to use foam because they like it, then you are a close-minded person. This hobby is all about preference and not everyone has to like what you like.

With that being said, let’s take a look at what foam is used for and discuss whether a keyboard should be designed to require foam?

While I haven’t been building keyboards for as long as some, I have built a lot and I’ve gotten a better understanding of how foam will change the sound created in an assembled keyboard. Foams and films are used to change the way that sound moves around in the keyboard. These foams and films can be in different areas and you can usually mix and match them to create the sound you like best.

Foams are usually used to fill in the cavity of the keyboard (usually at the bottom) in order to eliminate the metal-sounding ping when typing on the keyboard (or even when just tapping the side of the keyboard) and it’s used to alter or stop any sound from bouncing around inside the keyboard. Those sounds, by the way, might be your thing and so you don’t want the foam to stop those sounds. That’s great. It’s your keyboard and you should make it sound the way you want. Period.

My current favourite “foamy” sound signature comes from using the foam in between the PCB and the plate. Typically, placing the foam there offers a slightly deeper (sometimes quieter) sound while still allowing the sound to resonate on the bottom of the case. Bottom foam, described just above, is hit or miss for me. I find it best If a case has a lot of resonance, but the foam usually shaves off a lot of the mid-tone notes I like in a keyboard.

If you’re initially foam-averse, I do suggest you try Poly-Fil (that’s an affiliate link). It’s incredibly cheap and you don’t need to use much in a keyboard to reduce (sometimes eliminate) case resonance and ping.

Should a Keyboard Be Designed to Need Foam?


No. I think a keyboard should be designed to sound good without the use of foam. I know, it’s preference. If the sound out of a keyboard doesn’t sound good to you without foam was it poorly designed? I guess I mean having to rely on foam to cover up shortcomings of the design isn’t a good thing. An example of a shortcoming would be maybe the keyboard needed a weight in it to break up some sound, but to reduce some cost and take a shortcut it wasn’t added. Instead the use of foam would be used here.

Should You Use Foam?

Well, that’s up to you. But I do recommend you try using foam at least once if you never use it. Likewise, if you always use foam, consider leaving it out of a build initially to make sure you really need it.

In the end it’s your keyboard and you should build it the way you want to build and make it sound the way you want it to sound.