Acoustic Geometry for 3D Printed cases - Geekhack

Hello all.

As you may or may not be able to tell by a couple of my earlier threads, I have a bit of a focus on 3D-printed keyboards and designs.

I'm getting things together to offer a new throughole kit design, but I'm still experimenting with some design elements inside of the case. After opening up the lower case cavity to accommodate the PCB (and not having a handwired matrix to dampen the sound), I'm experimenting with the lower case model for different ways of diffusing the sound as it bounces back.

Has anyone else played around with this sort of thing? I'm wanting to find a way to take the edge off of the sound without the level of efficiency/print time sacrifice of just adding a bigger block of plastic to the bottom of the case. My initial thought is to add slopes/wedges to the lower case, but I've also considered smoother shapes like waves/curves, and even blocks of varying height. I'm looking to acoustic panels and padding to inspire these ides, but with the different materials, I think that's something that should be practiced with some reservations (at least for the results expected).


Thanks in advance for the discussion! It's too many variables.
You're dealing with several dozen of points of sound origin, not even accounting for how the switch body itself  and the pcb and plate will effect it. Worse, 3d printing isn't creating flat surfaces, the movements are digital, not analog and then you have a pulsing effect from the extruder, that would be a good thing were it not for the fact that it's all rounded off rather than squared off. Don't forget you have to account for how you print it as well, any changes to the bottom can effect the angle of the inner surface print and then you get into free space, infill, plastic type, etc... It's too many variables, all of which could be thrown off just by using the wrong slicing software.

In my experience, you're better of focusing on eliminating free space, plastic and infill type and amount to alter the sound, it's much simpler and won't compromise the external look.

help fill the empty space in a more material-efficient manner.

Honestly, the plastic in 3d printing is about the cheapest, most efficient method of filling that empty space.*

Foam or cotton works but that takes human time to do, can also be messy and not as nice looking to someone buying. Casting a silicone block looks and works well but go look up how much just the silicone will cost compared to the plastic it replaces... TONS more money and you still need mold release, cups, stir sticks, scale, and if necessary a degassing chamber, and it will increase shipping costs due to weight.  In total it adds a LOT of cost. Worse still, none will likely have as much effect as different plastics, infill % and infill style. They would still help, but those really only help mitigate other bad choices, they shouldn't be the first choice.

Plastic is cheap, and yes, it will take a few more hours but they are machine hours and if you're talking an extra 3 hours on a 24-36 hour print, it's a negligible amount.


*Before you get too far down this hole,
Do some testing because this is one of the traps of 3d printing people often fall down. Draw up a simple cube, check how long that print time is now punch a hole through it and check print time again. We think of holes as reducing material because you're working from the perspective of it being solid, in a honeycomb object traditional "lightening" methods are out the window because every wall means extra plastic. I know it sounds counterintuitive but until that wall removes more than the infill, infill is faster and cheaper and you'd be surprised just how efficient that infill really is. Any time you try and reduce print time or plastic make two versions and run them through slicer, often the difference is negligible at best and sometimes it's better to give up a little plastic for a much faster print.

help fill the empty space in a more material-efficient manner.

Honestly, the plastic in 3d printing is about the cheapest, most efficient method of filling that empty space.*

Foam or cotton works but that takes human time to do, can also be messy and not as nice looking to someone buying. Casting a silicone block looks and works well but go look up how much just the silicone will cost compared to the plastic it replaces... TONS more money and you still need mold release, cups, stir sticks, scale, and if necessary a degassing chamber, and it will increase shipping costs due to weight.  In total it adds a LOT of cost. Worse still, none will likely have as much effect as different plastics, infill % and infill style. They would still help, but those really only help mitigate other bad choices, they shouldn't be the first choice.

Plastic is cheap, and yes, it will take a few more hours but they are machine hours and if you're talking an extra 3 hours on a 24-36 hour print, it's a negligible amount.


*Before you get too far down this hole,
Do some testing because this is one of the traps of 3d printing people often fall down. Draw up a simple cube, check how long that print time is now punch a hole through it and check print time again. We think of holes as reducing material because you're working from the perspective of it being solid, in a honeycomb object traditional "lightening" methods are out the window because every wall means extra plastic. I know it sounds counterintuitive but until that wall removes more than the infill, infill is faster and cheaper and you'd be surprised just how efficient that infill really is. Any time you try and reduce print time or plastic make two versions and run them through slicer, often the difference is negligible at best and sometimes it's better to give up a little plastic for a much faster print.

The efficiency I'm most concerned with is the printing time - Turning up the fill density isn't off the table, but I'm hoping to keep myself under a 36-hour ceiling between the top and bottom prints to give me the best opportunity for print turnover as well.

No such thing as “acoustic foam” despite what the crooks at auralex marketing department tell you. You should be using oc703 or rock wool for acoustic treatments. Burlap or muslin for covering fabric. Anything else is a waste of time and money.

Yes. I'm aware of rock wool but don’t want to mess with that.
I might consider OC703 (looks less messy to work with).

We did actually a very good job over a friend studio using same method (foam in panels), we used polyurethane foam at a density of 30 kg per cubic + the sealing was covered with Melamine foam panels (no frames), the results were sufficient, the room is dry enough and quiet.
Both his room and my are made of concrete walls, the bass waves and overall feel is not good and you need to play loud to hear the guitar well, when practicing over a backing track it's even worse, all sounds like a mash.
Since it worked for his room to my taste and the rooms are more or less the same size, I decided to go with the same solution over my place..
I'm not looking for a recording studio quality, I'm not recording any vocals over there, this is only for practice / sketches.
Thanks.

Start with the corners, then do first reflection points. You need to get the low end under control, that means mass in the corners.

Interesting…..even if all the corners in my studio are packed?
I got the working desk on one corner, a 2 door closet on the other, the door to the room is on the left side of one of the walls (that’s the 3rd corner) and all my amps and cabs on the other side of the wall (the 4th corner).

There isn’t any corner exposed, unless you mean the sealing?

I used Ready Acoustics to provide an acoustics analysis of my room. I can't recommend this service enough. Especially for the low fee they charge.

Why invest all of that time and money only to be left with a sub-standard result. Assuming your knowledge on the subject is less than theirs of course.

https://www.readyacoustics.com/room_acoustics.html

They can sketch it up for you using images, dimensions, etc that you provide. I opted to sketch my room using Google Sketchup Free and send it to them. They then analyzed my room and sketched in the panels I would need for my room.

I then built my panels using Ownens Corning 703. I would second Matt's suggestion of purchasing their fabric. In fact, anything from RA that your budget will allow will make the project much easier and less time consuming - if not more effective (depending on the materials you purchase and use yourself).

Here's a snapshot of the Sketch they provided. Keep in mind, the Sketchup file you would get from them is 3D and modifiable. That program is very user friendly.



Here's a couple of pics of my treated room using the design they provided. I did not hang the 2 panels by the window on right so I can access window. I just position them when mixing.



Looks very nice and inspiring.
I'm not located in the US so buying their panels and importing it, make no sense for me.
I love doing these things by myself, the results are not always 10/10 but still it's something that looks good and hopefully will be effective.
I'm on a tight budget and as the materials are cheap, I prefer to do it by myself, I enjoy it so why not.
However, I might use their service for designing the panels according to my room data, I think I will give that a try.
Thanks.

Looks very nice and inspiring.
I'm not located in the US so buying their panels and importing it, make no sense for me.
I love doing these things by myself, the results are not always 10/10 but still it's something that looks good and hopefully will be effective.
I'm on a tight budget and as the materials are cheap, I prefer to do it by myself, I enjoy it so why not.
However, I might use their service for designing the panels according to my room data, I think I will give that a try.
Thanks.

Thanks Roadrunner.
I understand, not being in the US does make purchasing from them more costly. I agree, using their design service would be beneficial to your project.

If you find it helpful, here's how I built my panels.

http://vivretteguitaracademy.com/studio-remodel-february-update-week-2/

http://vivretteguitaracademy.com/studio-remodel-february-update-week-3/ I purchased the fiberglass boards today, the frames are ready too so tomorrow I will get the fabric and the plan is to finish all the frames during the weekend.
I gave it some thoughts, the front of course will be covered with some good light / breathing fabric but what about the back of the frame?
I saw a lot of good examples where they cover the back with a simple fabric.
Does is matters which material you use for the back?
I have a lot of thick nylon sheets which I can use for the back, what do you think? would it effect the results compared to a fabric back?

Just use the same fabric, it's much easier to get it taut. Are you using staples?

The fabric cost $$$ and the nylon is free, I already go it.
Using the nylon will reduce the fabric cost into half, I have 12 frames to build (I might build few more), most of them are 1 x 1 meter, thats alot of fabric .
Yes, using staples, i got a good electric gun for that, doing the job fast and tight.