Concrete Passive Speaker Cube




Introduction: Concrete Passive Speaker Cube

About: Hi I'm Linn and on my Youtube Channel I have lots of great videos about building, construction and fun projects. You can also check out my site @

This passive speaker is made out of concrete and wood. There's no wiring, no electronics, it's a pretty simple build, so it's a perfect project if you're looking to make your phone sound a lot better.

I find the concept of a passive speaker really appealing, because it means I can just put on some music or a podcast on my phone, immediately place it in the speaker holder, and that's it. No need to pair it to a bluetooth speaker, and no rechargeable battery to do deal with. Simple. I decided to combine concrete and wood, in some form of a cube shape, that way the speaker wouldn't take up a ton of counter space.

Step 1: The Molds

I'm using a stem glass to create the indention for the mold. At the Dollar store I got a bunch of nice plastic wine and cocktail glasses. I decided to make two new molds, and decide later on what shape was the best.

I'm using my woodworking tools to create the pieces for these molds, but another idea would be to use the bottom of a half gallon milk container or something like that - or why not make a mold using foamboard and glue. There are lots of ways to accomplish this.

Step 2: Drilling the Holes

Next, I marked out the center of the bottom piece and drilled a hole that was about the same as the thickness of the stems. Then I marked out where the screw holes needed to go, pre drilled, and connected the molds together. To prevent the concrete from sticking, I brushed the plywood and outside of the plastic glass with vegetable oil.

Step 3: Mixing the Concrete

I mixed some mortar, which is nice and smooth without any aggregate, so it's what I often use for these types of projects. I created a pretty loose mix, kind of like oatmeal.

Then I placed the glass in the middle, coming through the hole and then added the concrete mix around it. And I tapped it down a couple of times to remove any air pockets and level the concrete.

Step 4: Removing the Molds

A few hours later I unscrewed the pieces, removed the plastic cups, and was left with two pretty nice looking concrete forms. They both were nice, however I decided to use the mold with the wine glass indention.

Step 5: The Wooden Surround

I want to create a wooden surround, I'm cutting up a piece of mahogany, however any type of wood, would be great, whatever you have. I'm creating mitered corners here for a nice framed in look.

The idea is to have the concrete cube in the middle and the wood surround on all sides.

Step 6: Gluing the Support Pieces

I want the phone to sit just above the hole which will direct the sound outwards, so I'm making a mark and then I'm cutting up some scrap pieces. And I'm gluing those one with polyurethane glue which attaches well to concrete.

Step 7: Chiseling the Slot

Next I'm marking out where the phone should sit within the top wooden piece. First drilled some holes to remove as much wood as possible. And then I used a chisel and mallet to clean it up. To round the edges a bit, I used a file and then sandpaper.

Step 8: Glue-Up

Time to glue the wood together. And I'm using this simple technique where masking tape is acting as clamps. Then I wanted to confirm that the concrete piece was going to fit inside, which it did perfectly.

Step 9: Gluing the Concrete to the Wood

Once the glue dried, I sanded the wood, and then glued the concrete cube in place here, again with some polyurethane glue. I also have a piece for the back here and I glued that in place as well.

Step 10: Finishing

Finally, time for finishing. I used two coats of dewaxed shellac first, and then I put on some of my tung oil beeswax polish.

Step 11: Conclusion - Watch the Video

For a much better perspective and to view the final result, make sure to watch the video that goes over the complete build.



    • Tiny Home Contest

      Tiny Home Contest
    • Creative Misuse Contest

      Creative Misuse Contest
    • Metalworking Contest

      Metalworking Contest

    14 Discussions

    great job!

    This is actually a really good looking speaker box and it seems so easy to make even! You could probably do the same on a larger scale if you need more amplification or even just tweak the design to create a pretty stylish storage box for your home! I would definitely explore this idea a little bit more since it's most certainly going to be a fair amount cheaper than paying for an actual huge speaker box set!

    Very nice project. I'm going to build this but with a couple of minor differences. First, I'm going to use a plastic funnel from the dollar store for a more conical geometry, and second, I'm going to mitre the rear cover to give the cub a completely seamless appearance.

    Well done, my only complaint is that Blue Apron isn't available in my area :(

    incredible work, simple amazing.!!

    Hi darbinorvar,

    This is the first video, of yours, that I've viewed. Very, very good job! I have four major points to make about your project and presentation.

    First, I want to compliment you on your creativeness and "thinking outside the box". Most of us, as adults, lose that skill but can renew it by building projects like yours and others who present their ideas on Instructables.

    Second, your project lends itself to experimenting and renewing our "thinking outside the box" skills along with learning something about the physics of sound. One could change the shape, depth, and size, of the concrete cube and its enclosure, on a trial and error basis, to determine which parameters give the best or desired results.

    Third, your mechanical skills are excellent! I like your wooden mold idea and using the veggie oil to prevent the concrete from sticking to the surfaces of the mold and the plastic wine cup. I also like the idea of using the blue tape to assemble and hold your final enclosure together, while the glue dries. Miter joints can be difficult to assemble but you've simplified that step for this project.

    Fourth, your video and presentation, of your project, from your initial idea, drawings, failures and successes, that led to a final tangible working product was excellent! You've included the very details needed to achieve success in duplicating your passive speaker cube.

    I will be making one and experimenting with different sizes and shapes.

    Thanks and keep making more great projects!


    Very captivating video. A great idea. I like that you showed a "failure" too. Awesome!

    Very nice idea - and well done. Thanks for sharing.

    Very nice idea


    1 year ago

    My goodness, an appropriate use of urethane glue! Well done!


    1 year ago

    This project is a neigh for me, but I do like your tape method for clamping...

    Hi Darbin

    One more great invention you have made that it so really cool and fascinating, hope to do one for myself soon. Thanks a lot.

    You have such great inventious and does that in the best way of quality. I've just found your work here and still have a lot to see. Bu I just feel myself already a big fan of you! Keep on doing this amazing job!!!

    Great work, thank you for sharing :)