Keyboard Cases: Stuffed or Hollow?

[Hypersphere]

Do you prefer to keep your keyboard cases hollow or to stuff them with foam or other sound-deadening material? I suppose it depends on many variables, including case design, case material, switches, and a preference for a hollow reverberation vs a deadened sound.

If you do use foam or other sound absorbers, what particular material do you use and how do you use it? For example, do you fill the case so that it is under noticeable tension when putting it back together?

Before and after audio recordings would be most welcome!

[fohat]

do you fill the case so that it is under noticeable tension when putting it back together?

Putting a plastic case under almost any amount of tension will cause it to deform and not sit properly flat. Even Model Ms warp with surprisingly little internal pressure.

[pyrelink]

In most of my plastic case'd keyboards I add some drawer liner into the bottom shell, under the PCB. I have some in my HHKB even. It is just a single sheet so its not putting the case under any amount of tension. Generally I find the result to be pretty small, but it does seem to eliminate a little bit of the reverberation. I could try to take some before and after sound clips though.

[Hypersphere]

Some time ago, I put a KBP V60MTS-C into a TEK CNC aluminum case, which is merely a metal tray with virtually no potential for reverberation. It looked nice, but the aluminum case made the Matias Click switches sound higher-pitched and dead at the same time. I ended up going back to the stock plastic case, which has more hollow spaces and thin walls capable of some vibration. The keyboard sounded much better in the cheap plastic case, which also doesn't look all that bad.

At the moment, I am typing on my newly refurbished LE DC-3014 blue Alps board. I did not put any foam inside, and I rather like the hollow reverberations, which are reminiscent of the celebrated "thock" of Topre-switch keyboards. I might try adding some interior foam later to see which version I like better -- stuffed or hollow.

I do, however, like quiet spacebars. To this end, I replaced the slider and click leaf on the spacebar spring with the corresponding parts from a Matias Quiet switch. I also put rectangles of thin polyurethane foam (0.5 mm) under the spacebar where the stabilizer inserts hit the plate. I didn't use the original pads because I replaced the spacebar and stabilizer with a 7.00x black spacebar from Matias -- the inserts on this spacebar are wider apart than on the stock LE. Result -- a spacebar with an agreeable low-pitched thunk and no rattle.

[Wodan]

I did some experiments with pouring liquid, hot wax into keyboard bottom shells. In my experiment, it was a simple, cheap Chinese 60% case. The biggest problem was closing the obligatory opening in the bottom for the reset/dip switch.

It did work pretty well though, next step would be placing a bunch of beefy metal nuts in the bottom case and then pour the wax over them to create a heavier, solid bottom weight. This method can be used to fill the bottom case till just under the pcb and then just add a very thin layer of foam/cotton.

[Hypersphere]

Paraffin-filled keyboards sounds rather messy, but in the end, you would also have a nice neutron moderator!

[fohat]

http://imgur.com/a/I17XX

[Khers]

When changing some switches in a keyboard of mine, I gave some thought to how the case affects the sound of a keyboard. I had an Alps custom built with linear-modded dampened creams put in a Tex acrylic case. As the linear-modded creams are about as silent as a mechanical switch will ever be, a keyboard built with them is pretty much case-agnostic when it comes to sound. However, swapping some SKCM blues into that keyboard highlighted some serious short comings of the case's resonance chamber when coupled with more vocal switches.

Since I already had a 60% built up with blues, I knew roughly what to expect; a sound signature that is surprisingly bassy. What I found was instead something sounding discomfortably close to MX blues. (This should be taken with a rather generous grain of salt though as it was quite some time ago that I sold my last MX blues - the reason being I couldn't stand their atrocious sound signature.) As the switches seemed fine outside of the keyboard (they sounded like any other SKCM blues I had on hand), it was quite clear that the case was at the root of the unpleasant sound. As Hypersphere points out, the resonance chamber beneath the PCB on these Tex cases is infinitesimal and, while I'm neither a musician nor a sound engineer, my guess is that this small volume is incapable of amplifying the full sound of the SKCM blues.

I didn't try any dampening material in this case, instead I swapped the board into cheap Poker 2 case clone I got off of Aliexpress. While the sound was better, it was only marginally so. The sond gained some of that bass that is what you want from an SKCM blue, but it sounded very tinny. As it seemed to me that most of what I wanted was present, but tinny, I though that I could mitigate that by adding some dampening material. Searching through the house, I took whatever I thought would fit the bill and two pieces of thin shelf liner I'd gotten from the hardware store. What a revelation. All of a sudden, it sounded like the rich SKCM blues I was used to hearing, but with a little inconsistency between the different rows, so that'll need further tweaking.

Now the funny part of this is that the SKCM blues that I'm used to hearing are in a hammer-clone aluminium case with a resonance chamber only fractionally larger than the one in the Tex. Despite this, they emit plenty of bass. Hence, the resonance chamber can't be all there is to it. Material certainly plays a role as well, though, with Hypersphere's testimony of an aluminium Tex and Matias Clicks, it's more than unclear to what extent.

[Hypersphere]

@Khers: Interesting. I recall that when I put my V60MTS-C into the TEX aluminum case, the switches sounded like Cherry mx blues. This was quite irritating, and so I promptly moved it back to the stock plastic case.

Imagine the sound of your keyboard in this room:

insideviolin1.jpg (82.17 KiB) Viewed 7034 times

One of the ultimate sounding boards -- the inside of a violin.

It is easy to imagine that paying more attention to the design of keyboard cases could have a major impact on the sound of the keyboard. Perhaps rather than trying to dampen the sound, we should work on tweaking the case to get the desired acoustic effect. However, acoustics is still a complex mixture of art and science. We still don't exactly know what makes a Stradivarius sound like a Stradivarius (in the hands of an expert violinist).

As far as I know, not too many violinists elect to stuff their violins with foam.