Super-thin 3D printed DIY speaker

[mcdn]

In my study I have a TV with a Sonos Ray doing audio duties. It's OK but I thought I could do better so I designed something to fit my needs:

• Less than 50mm (2") deep
• Stereo pair to go either side of the TV
• No more than 80dB/1m average SPL needed. the room is 4x3x4LWH and the listening position is about 2.5m from the speakers
• Wide dispersion, this is a personal preference but it also helps in the small room to avoid rear wall reflections being too much of an issue if the sound power isn't being beamed in a straight line to the MLP
• F3 50Hz @ 80dB/1m

I chose the Dayton LW150-4 shallow woofer for duties from 50-400Hz. 400Hz and up is handled by the Tectonic TEBM35C10. There's no passive crossover, these are active speakers with external amps and DSP. Simulation in VituixCAD shows the goals should be met with these drivers.

The enclosure is a bit of a challenge being so slim. After prototyping with my small home 3D printer I was happy enough to send a full sized job off to JLC for printing in resin. It's 5mm thick so will have some challenges with resonances. I will be gluing aluminium sections to the front and back panels to increase the stiffness, and will post before and after measurements.

Stay tuned!

 

[kemmler3D]

I think this is a fascinating project, and I've thought often about 3d printing a speaker, maybe my username is a clue...

It would actually be really interesting if you could take a measurement with and without the aluminum panels. I would be wondering about the 5mm thickness and resonances / cabinet vibration myself, so I'm curious if my concern would be justified and how much so.

If there are issues I guess you could always print some braces and glue them in place, so in the end i am sure this will come out great.

Any plans for a paint or veneer finish? Or maybe you'll go for electroplating?

 

[mcdn]

I think this is a fascinating project, and I've thought often about 3d printing a speaker, maybe my username is a clue...

It would actually be really interesting if you could take a measurement with and without the aluminum panels. I would be wondering about the 5mm thickness and resonances / cabinet vibration myself, so I'm curious if my concern would be justified and how much so.

If there are issues I guess you could always print some braces and glue them in place, so in the end i am sure this will come out great.

Any plans for a paint or veneer finish? Or maybe you'll go for electroplating?

Yeah your username is a bit of a giveaway, I love your diffuser project!

The aluminium sections are 12x12x1.5mm U shapes, which glue very nicely onto the resin parts with superglue. I have an accelerometer to measure panel resonances before and after. The difference when I measured with my home-made parts was huge - Aluminium is just ridiculously stiffer than any kind of plastic. @RickS has a thread about panel stiffening which is what inspired me to go light on the prints and add stiffening after.

As for painting, yes, the resin is slightly yellow in colour. I'll spray a plastic primer, white enamel, then semi-gloss clear coat.

 

[Roland68]

Yeah your username is a bit of a giveaway, I love your diffuser project!

The aluminium sections are 12x12x1.5mm U shapes, which glue very nicely onto the resin parts with superglue. I have an accelerometer to measure panel resonances before and after. The difference when I measured with my home-made parts was huge - Aluminium is just ridiculously stiffer than any kind of plastic. @RickS has a thread about panel stiffening which is what inspired me to go light on the prints and add stiffening after.

As for painting, yes, the resin is slightly yellow in colour. I'll spray a plastic primer, white enamel, then semi-gloss clear coat.

That is actually already a thing of the past.
In the last two years, various extremely stable printable plastics have come onto the market that can compete with normal aluminum, in some cases even with 6061-T6.
This also includes nylon or PC with a high carbon fiber content. PPA-CF achieves a stiffness/bending modulus of almost 10,000 MPa, strength/bending strength of 208 MPa and tensile strength of 172 MPa. In addition, it is heat-resistant to over 200 degrees.

We already use a few materials in production and it is astonishing how many places aluminum can be replaced.
Above all, you can have much more influence on structure, stiffness and resonance optimization when printing.

 

[kyuu]

This is an interesting project, thanks for sharing. I wonder if the combination of 3D printing and active crossovers can overcome any of the issues with extremely small/thin enclosures. Even giants with excellent engineering resources like Kef haven't been able to get them to perform well.

Also seems like if the cabinet needs reinforcement to prevent resonances you could just print a new one with the reinforcement integrated rather than having to glue in separate pieces.

 

[kemmler3D]

That is actually already a thing of the past.
In the last two years, various extremely stable printable plastics have come onto the market that can compete with normal aluminum, in some cases even with 6061-T6.
This also includes nylon or PC with a high carbon fiber content. PPA-CF achieves a stiffness/bending modulus of almost 10,000 MPa, strength/bending strength of 208 MPa and tensile strength of 172 MPa. In addition, it is heat-resistant to over 200 degrees.

We already use a few materials in production and it is astonishing how many places aluminum can be replaced.
Above all, you can have much more influence on structure, stiffness and resonance optimization when printing.

This is true, but for home users it's harder to work with these filaments, and they are expensive compared to "standard" stuff like PLA or PETG. I think OP's print was probably done in nylon on an SLA printer but not sure. If I were going to build a speaker myself, I would not go for nylon / PC or CF, I'd just make something out of ABS, add a void to fill with concrete to improve stiffness and mass, and stick with that.

That said, a CF filament for a speaker enclosure is an interesting idea. Homemade magico-level performance?

 

[mcdn]

PPA-CF achieves a stiffness/bending modulus of almost 10,000 MPa, strength/bending strength of 208 MPa and tensile strength of 172 MPa. In addition, it is heat-resistant to over 200 degrees.

PPA-CF is amazing, but it's still only 14% of the stiffness of aluminium (10GPa vs 70GPa) and is rather expensive to print with at USD200/kg.

 

[mcdn]

This is true, but for home users it's harder to work with these filaments, and they are expensive compared to "standard" stuff like PLA or PETG. I think OP's print was probably done in nylon on an SLA printer but not sure. If I were going to build a speaker myself, I would not go for nylon / PC or CF, I'd just make something out of ABS, add a void to fill with concrete to improve stiffness and mass, and stick with that.

That said, a CF filament for a speaker enclosure is an interesting idea. Homemade magico-level performance?

It's JLC 9600 SLA resin (https://jlc3dp.com/help/article/photosensitive-9600-resin), chosen mainly because it's the cheapest option and in the same range of stiffness as most other materials whether SLA or FDM. It was still $100 per speaker plus shipping. Experiments on a PLA+ prototype I made at home showed the aluminium channels were very effective at pushing resonances up in frequency.

If you wanted Magico performance from a 3D print you'd be needing 70mm thick walls of the PPA-CF!!

 

[Roland68]

PPA-CF is amazing, but it's still only 14% of the stiffness of aluminium (10GPa vs 70GPa) and is rather expensive to print with at USD200/kg.

Please don't be mad at me, but you're really on the wrong track with GPA (modulus of elasticity) as a comparison.
Copper is definitely softer, more flexible and easier to work with than aluminum, but copper still has a GPa of 100-130!
Just as a hint, MDF boards of 16, 19 or 22mm have a GPA value of around 2.2 and is that enough even for larger boxes?

This could be achieved or exceeded with various printing materials, e.g. PET or PC (but also others) with glass fiber/carbon fiber and 25-40% infill, around € 25-50/Kg.
If the filling is printed with a Honeycomp structure and wall thicknesses optimized for low resonance with reinforcements incorporated in the Honeycomp structure, this should produce significantly better results than any concrete or plaster fillings. And depending on the size of the speaker, 10-20mm wall thickness for the infill is really enough.

I just want to point out to you and other interested users that 3D printing materials are already much more advanced.
Markforged and other manufacturers had already shown in 2021 that aluminum parts can be replaced with FDM printing processes and even surpass them thanks to intelligent construction.
It's not just on Mark3d.com that you can see examples from industry where massive and highly resilient aluminum parts have been completely replaced by FDM printing and have also passed all stress tests.
This extreme strength and stability is certainly not needed for loudspeaker housings.
And as I said, we now print various CF filaments and use them to replace highly stressed aluminum parts in mechanical engineering without any problems.
This shouldn't degenerate into a discussion and since I don't want to pollute your thread any further, I'm out.

 

[kemmler3D]

this should produce significantly better results than any concrete or plaster fillings. And depending on the size of the speaker, 10-20mm wall thickness for the infill is really enough.

I think this is probably true, or at least I don't doubt it, as far as flex / resonances go. However, the transmission loss of a relatively low density plastic panel has got to be less than MDF or concrete, right? I would be (vaguely) concerned about the lack of mass in the cabinet walls letting sound through.

I think CF filaments are great for applications where good mechanical properties are needed... but I think they may not be cost-effective or really needed for most speaker housings.

 

[mcdn]

Please don't be mad at me, but you're really on the wrong track with GPA (modulus of elasticity) as a comparison.
Copper is definitely softer, more flexible and easier to work with than aluminum, but copper still has a GPa of 100-130!

Don't go! This is not a place for anyone to get mad, it's for learning! SpaceX make their engines with 3D printing, and plastic parts can also have astonishing performance. No argument there.

I think the problem with copper as an example is twofold. On one hand it has a really sharp transition between being stiff and being ductile (i.e. between elastic and inelastic deformation). In layman's terms it's hard to bend it, but once you do it stays very bendy. This is because it has a low yield strength but high youngs modulus. On the other hand people are used to copper in small wires or thin sheets or thin-walled pipes. So their intuition is that copper is "bendy" because it is usually used in thin applications. Whereas a 1mm thickness copper pipe is easy to shape into a bend, a 1mm aluminium pipe would just break in two. Copper can both be stiffer within its elastic regime and more ductile, there's no real contradiction. Make a speaker cabinet from 5mm copper and it'll be super stiff because it never deforms.

Therefore for speaker cabinets specifically we really are mostly concerned with youngs modulus (or modulus of elasticity, slightly less well defined and usually around the same number anyway). This article from Audioholics is super useful: https://www.audioholics.com/loudspeaker-design/detailed-look-proper-loudspeaker-cabinet-bracing

MDF itself is attractive mainly because it is cheap, easy to work and "good enough". It still requires extensive bracing even in small cabinets, see the KEF LS50 white paper for an example: https://assets.kef.com/documents/ls50/20-KEF-LS50-Collection-WhitePapers.pdf

That's why I reckon a "good enough" shell with aluminium bracing hits a pretty good price/performance point. We shall see when I measure

 

[somebodyelse]

Have you considered a metamaterial wall instead of an ordinary infill? Probably a lot of work without some software to fit the different length channels in, but the voids in the sandwich are then doing double duty.