3d Printed / Poured Concrete enclosure concept

[lunchmoney]

Hey there Tech Talk,

I'm looking to make some small, wall mounted surround speakers for my home theater... I will eventually create a proper thread in the Projects Gallery, but for now want to get your thoughts on the basic concept here.... This design will be based on the Chito HT design, using the using the RS100-4 woofer and ND16 tweeter.... big thanks to Navy Guy for the hard work on the Chito. See the link here for more info....

http://techtalk.parts-express.com/fo...0-4-and-nd16fa

My idea is to 3D-print a double-walled vented enclosure that I will then fill with concrete. No mold to remove or anything, just fill it, let it cure, and it's done.

Overall dims are 10.5" tall x 8.25" wide x 4.25" deep. The volume is 1.7 liters with a 1.125" x 6.5" port, as per Navy Guy's specs. It's not quite a cylindrical port as you can see; although the cross-sectional area of the port is exactly the same as a 1.125"....

The overall thickness of the wall is 5/8", with 3/8" of concrete at it's core, and .5" of concrete on top.... I think it should be feasible, based on small DIY concrete flower pot projects that I've seen....

The first few pictures show the 3D-printed enclosure before the concrete pour. Note how the port is formed right into the enclosure, so no need to add a port.









Here you can see after the concrete is poured.... note how the concrete is poured from the top, shown in light gray here...











Here you can see the bottom of the enclosure, with the 3D-printed cover in place (yellow, no screw holes yet)... the crossover will be on the top of this cover. for easy access.



Other thoughts:

• The inside walls with be lined with 1/2" foam.
• It will be crossed with a big 12" sub at 80 hz, so low-end performance is not super critical... that being said, it should play fairly well full-range, as it is the correct
• 4 beefy eyelets (not shown) will be designed into the back for secure wall palcement.
• Terminals will also be on the bottom cover.
• The port does have a slight flair at either end, although I don't imagine this will be terribly meaningful for such a small speaker.

So.... what does Tech Talk think? Am I barking up the wrong tree here?

Thanks

Dan

[Billet]

Seems like a good idea to me. Should pass the "knock" test.

How much will it weigh?

[3rutu5]

I might have missed something but is this a concrete filled 3d printed project or is it just the cast?

[lunchmoney]

I might have missed something but is this a concrete filled 3d printed project or is it just the cast?

It's a 3D print that's filled with concrete. Both the print and the concrete are part of the finished speaker.

[lunchmoney]

Seems like a good idea to me. Should pass the "knock" test.

How much will it weigh?

About 9 pounds without drivers or crossover.... shouldn't be too bad.

[tomzarbo]

What kind of concrete do you intend to use? Most of the redimix stuff has aggregate of around 3/8" or a bit bigger... Maybe mortarmix with some added fiberglass fibers for strength? Not questioning, I'm sure you have a good idea if how to do it, just curious.

Looks like a pretty cool project. You control the look on the outside, the concrete creates extreme rigidity inside. Someday I'm gonna get me one of those 3d printers!

TomZ

[Chris Roemer]

I'd be curious as to how this would compare to one filled with (expandable) foam?

[scholl]

Multiple schools of thought. Build dense heavy boxes to sink vibration. Build light boxes to dissipate vibration quickly.

[lunchmoney]

I'd be curious as to how this would compare to one filled with (expandable) foam?

My assumption is that the higher density of the concrete would be preferable... would it not?

[lunchmoney]

What kind of concrete do you intend to use? Most of the redimix stuff has aggregate of around 3/8" or a bit bigger... Maybe mortarmix with some added fiberglass fibers for strength? Not questioning, I'm sure you have a good idea if how to do it, just curious.

Looks like a pretty cool project. You control the look on the outside, the concrete creates extreme rigidity inside. Someday I'm gonna get me one of those 3d printers!

TomZ

I'm not sure exactly what kind of concrete to use, but it seems like it would be possible, based on a gazillion small concrete flower pots out there, many of which are DIY. Looks like a fun hobby actually, there are lots of premade molds you can buy.

[lunchmoney]

Here it is with the drivers in place.... is the spacing between the woofer and the back wall ok? I'm assuming so, based on how I've seen some drivers packed into some micro monitors these days... the PE Passive Aggressives come to mind...

[gregrueff]

Based on augerpro/Brandon’s recent experiments on CLD, it’s interesting to think of filling it with a foam or rubber or caulk. The controversial and interesting character Xmax did this before he passed (caulk as I recall).
cement with fiberglass chopped matte sounds sexy too. Or maybe a rubber aggregate.

whatever you decide Lunch, I look forward to your stellar thread as always.

By the way, that spacing looks fine to me. Plenty of room to breath with you backside chamfer.

Cheers,
Greg

[randyohoh]

Standard silicone caulk has acetic acid in it and the fumes are corrosive especially in a contained space. There are electrical grades which are acetic acid free but I don't know if the big box stores carry it..

[randyohoh]

You might consider using mortar as the base material since there are no stones in the mix and structural strength isn't a major concern. DIY gardeners who make their own large homemade pots make something called hypertufa which is a mix of one part mortar, 1-1/2 parts sphagnum moss, and 1-1/2 part perlite plus water. This significantly lightens the mix up. I have also seen people grind up styrofoam packing material into pea sized pieces and mix it with mortar to lighten up homemade pots. I'm not sure of how that would work acoustically but the materials are all inexpensive and the mix could be tweaked if necessary.

[lunchmoney]

Sounds like there's a number of options for a suitable fill material, and I've got some research to do... an important factor no doubt will be "how well does it pour".

Weight is not really a concern here, as they're so small. Even if I used concrete they should still be under 15 pounds.

Thank for the feedback everyone. I think I'm gonna go for it.

[Rory Buszka]

I'd be curious as to how this would compare to one filled with (expandable) foam?

Expando-foam will expand and separate the layers of the 3D printed form. It expands with a considerable amount of force, enough to split plywood.

[Billet]

Sand?