Material comparison for plate (PE) foam mod (with my tests)

PE foam mod – one of the most known keyboard mods. At least that’s the mod that you hear all around the web. I’ve made a detailed guide to help you both understand the nature of this mod and perform it yourself. You can read it here – ARTICLE PE FOAM MOD

I’m writing this article to help you choose the right foam for the PE foam mod, or as I like to call it – plate foam mod. Let’s get right into it!

What foam should you use for the PE foam mod?

Do you know what’s the best thing about this mod? You can choose a foam yourself. That with the custom method I talk about in my article about PE foam mod enables you to make your keyboard unique. Entirely special.

But before you start experimenting a few important aspects that we need to talk about:

The foam that you choose can’t be hard. It needs to be easy to pierce by the keyboard’s switch’s delicate pins. Ensure that the material you choose is somewhat similar to PE foam in softness.
Don’t use materials with strong adhesive. It’s better if the foam you’re using doesn’t have any glue at all. It will be safer and easier to remove if you don’t like the result.
Be careful. It is very important that you perform this mod with a lot of caution. Especially when experimenting. It’s easy to bend your switch’s pins and damage your PCB if you rush or push the switch too hard.

With that being said you can find a great foam yourself. The one that YOU like the most.

Now, I don’t have the tools or resources to test the foam material myself in a scientific way. But I will talk about a few materials that you can use in my own (a bit less scientific) words.

PE foam

First, we need to talk about the PE foam. This is, in fact, the material that this mod originated from. For that, I will use the information discovered in this scientific study – PE FOAM STUDY

In the document, you can read the whole process of the PE foam material examination. Here I will give you an important graph that represents the results of this study:

This graph is taken from the study paper by Universiti Tun Hussein Onn Malaysia Publisher’s Office and belongs to the authors of this paper

This graph shows the frequencies which PE foam tends to absorb as well as the frequencies it tends to strengthen.

Let me put this information in a simpler way to understand. This means that the lower sounds of your keyboard switch get suppressed. The middle sounds are stronger and louder. And again, the higher sounds are suppressed a bit less.

PE foam makes the keyboard’s sound shift towards the middle frequencies – less high-pitched sounds and less low-pitched sounds.

That’s why PE foam makes the keyboard sound a bit like marble. PE foam is for you if you want to raise the sound of a low-pitched switch or lower the sound of a high-pitched switch.

Acoustic foam

Acoustic foam – this is my favorite material to use when modding a keyboard. I’ll do my best not to be biased. I will present this material in an objective way so that you know if it’s the right one for you.

There are a few studies of the acoustic foam sound absorption coefficient depending on the frequency. Here I will show you one of the graphs that represent the properties of this material:

On this graph, you can see that the acoustic foam doesn’t absorb much of the lower frequencies and it absorbs more and more as the frequency raises. But what does it mean for us? For this particular mod?

Acoustic foam will make your keyboard’s sound shift toward a lower end. Thanks to the suppressing properties of acoustic foam for higher frequencies your keyboard’s sound will shift towards lower frequencies making it sound more “bass”.

I like keyboards that sound low. That’s why I love acoustic foam. This material is not fittable for people who like the sound of clicky switches, it will make them less clicky. Acoustic foam fits mostly linear and sometimes tactile switch builds.

However, a bit downside of this material is that it’s not very reliable. You can easily squish it too much because it’s quite soft. Sometimes, depending on the particular acoustic foam that you buy, you might need two layers instead of one. Or a thicker piece.

Acoustic foam with aluminum (on the bottom)

Now, that’s an interesting material. Combining acoustic foam which tends to make your keyboard have more bass with the sound-absorbing properties of aluminum foil if placed next to the source.

A quick tip for you: you don’t need to buy „acoustic foam with aluminium on the bottom”. Most of them have this metal on top. You need to simply place it upside-down.

This material has great use in our plate foam mod. Aluminium has in theory around 80% sound cancellation rate if placed near the sound source. This means that you can prevent the sound from ever entering the lower parts of your keyboard using this material in this keyboard mod.

This also means that acoustic foam with aluminum will reduce the effect of any mods placed below it. Mods like tape mod or case foam mod.

Acoustic foam with aluminum used in plate (PE) foam mod will reduce the effect of any mods placed below the material. It will also reflect most of the sound. It affects the keyboard’s sound the most if the aluminum is on the PCB side.

Imagine that sound-reflective aluminum is on the PCB side. In such a situation the sound that the switch produces goes through the acoustic foam once. Then the sound waves hit aluminum and most of them get reflected back through the acoustic foam. It filters the sound two times!

Acoustic foam with aluminum is an amazing material that strengthens the properties of acoustic foam (if placed with aluminum on the bottom). Thanks to that your keyboard will sound lower (just like with acoustic foam) and quieter. However, this material will greatly reduce the effect of any mods below it.

There are limitless materials that you can use as foam in the plate (PE) foam mod. I encourage you to try a few yourself. Especially if you have some lying around already. A packing foil for example.

I can’t test some of those materials. Well, I could but a packing foil is different every time you purchase something. It’s better (and hopefully more fun) if you check a few materials yourself.

I developed my original PE foam mod method that lets you test multiple materials without committing to one of them for a whole keyboard. It’s also safer. You can read more about this method here – MY PE FOAM MOD METHOD

I wish you safe experiments. And if you don’t want to try materials for yourself you can always use the PE foam. Just be careful when performing the PE foam mod on your keyboard. It’s easy to damage something.