Okay, so here we go, my first instructable.
After purchasing some new speakers
(http://dali.nl/producten.html?page=shop.product_de...) I decided that it would be nice to build some new speaker stands. I did this before for my previous speakers, but those stands were smaller and made mainly from MDF.
My new speaker stands will be made out of concrete! The idea is that the heavy concrete will not transfer any vibrations from the speakers to the floor. I dont know if that is really true, but it is a cool project anyway.
I made 2 stands, but the instructable will describe the build process for just 1.
The layout of the speaker is as follows:
- big concrete slab as the floor plate
- hollow concrete tube to get to the right height (hollow because the speaker wire goes through)
- smaller concrete slab to support the speaker
Step 1: Mould for the Top Plate
I made the mould for the top plate from the type of plates that are used to cast concrete foundations (in Dutch: bekistingsplaat). I made this plate first, because this plate is smallest and lightest, and easier to use upside down.
I took the size of my speakers (162 x 220 mm) to make the mould, and the thickness of the plate will be about 30 mm. I drilled a hole in the center of the mould, and placed a 30 mm PVC tube in the hole. This PVC tube is the reason the stand is hollow.
The yellow tacky tape is to create a removable space for the speaker wire to reach the backside of the speaker, coming from the hollow tube.
I used metal mesh as reinforcement for my concrete, and I tried to make sure that the reinforcement bridges the different concrete elements that I was making. There is metal mesh in the plate, and metal mesh around the PVC pipe.
Step 2: Mixing Concrete and Casting Top Tile
I selected a concrete with a smooth surface finish, based on sand and cement. I believe the English word is screed, in Dutch it is zandcementmortel.
Follow the instructions on the bag for your specific concrete. I also added black pigment to darken the concrete. Any damages to the finished stands will be less noticeble this way I hoped.
Pour the concrete in the mould, and smoothen the top surface. Don't be alarmed when water gathers on top of your mould, just keep checking the surface of the concrete stays level. Poke the concrete around a bit with a stick, but be careful not to displace the wire mesh.
Tip: mix enough concrete to fill the mould in one go, multiple castings will not improve the quality of your stand
Tip2: if you carefully weigh out your concrete, you can always add the same ratio of pigment to prevent differences in colour.
Step 3: Prepare the Tube
While the first tile is drying, you can prepare the tube. Again the reinforcement is wire mesh. I used a spare piece of inner pipe to prepare my reinforcement. As you see, I used a small diameter PVC pipe to create a hollow core in the tube and a bigger PVC pipe for the outer diameter of the tube.
The ratio of the inner and outer PVC pipe must not be too small: the resulting wall will be too thin, it must also not be too big, otherwise the part will be heavy.
Note about the length of the tube: I chose the length of the tube such that the total height of the speaker + stand will be 880 mm. This way, the total height matches that of the Dali Zensor 5 floorstanding speakers (http://www.dali.nl/producten.html?page=shop.product_details&product_id=71&flypage=flypage.tpl&pop=0)
Step 4: Casting the Tube
When casting the tube, be sure to have some kind of long thin stick so you can poke into the concrete to get out all the air bubbles.
I tried to prepare the outer PVC pipe for easy releasing after casting by greasing it up with some WD40. Although this failed it is still a good idea to solve this problem, as you will see in the next step.
Step 5: Removing the Outer Pipe
After the concrete had dried, it wouldn't release from the tube, so I had to do some destruction.
With a paint stripper, I heated up the plastic and cut it away with a hobby knife. Beware that heating PVC creates toxic smoke so protect yourselves. I used a 3M industrial mask, which worked great.
Step 6: Casting the Bottom Tile
The next step is casting to bottom concrete tile. The difficult part is to fix the tube with the top tile in a way that it doesn't fall over and stays exactly level with the bottom tile.
As you can see in the last picture, a small part of the inner tube is still sticking out. Drill a hole in the bottom mould plate to stick this piece of tube in. This way you can fix the tube with respect to the mould of the bottom tile, and create an open connection between the top and the bottom at the same time.
Step 7: Finishing Up
After the bottom tile has dried, remove the mould, and paint your speaker stands. As you can see, the black pigment did not really work. I would not use it the next time, also because painting turned out fine.
Finally, add some floor protectors under the bottom tile, and some dual sided tape on the top side to fixate your speaker on.
Step 8: What Went Wrong
Not everything went right straight away. Things I encountered:
- Chipping of corners
- Breaking away a piece of tile: while casting, the wire mesh floated to the top of concrete, so I hammered a nail into the side of the mould to keep it down. Unfortunately, when demoulding I had forgotten about that and broke away a piece of tile with the side of the mould which had the nail.
- not mixing enough concrete for a complete tile or tube. Not a big problem, but mixing new concrete with slightly different ratio might create a weak spot in your product.
- Removing of the outer PVC pipe on the tubes weakened the connection between the tube and the top tile. It still holds, but I think that the concrete is broken and the metal mesh holds the pieces together.
- Use a wooded spatula to create the room for the speaker wire in the top tile, don't do what I did.
- The problem with this order of working is that the sides of the tiles on contact with the mould are nicest and smoothest. In this case, those are the top surface of the top tile and the bottom surface of the bottom tile. These two surfaces are both not visible. The top surface of the bottom tiles are visible, but certainly not as smooth. By making some kind of mould which is closed at the top, the tiles could be produced with smooth top and bottom surfaces.
Good luck with creating your own speaker stands. This project was made in September/October 2015. I'd love to hear any comments or questions.