Building a DIY concrete speaker | Cinematic build video

My plan was to build a high-end reference speaker cabinet. The only problem we had was the concrete mixture. The concrete didn't bind properly for over two weeks. The first cabinet we got out of the mold completely broke because of that. The second cabinet has major cracks, which cause instabilities.
I will build this speaker with MDF and start a smaller concrete Project the next time.
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[@marcellominasi41]

To prevent breakage, especially in large and relatively thin slabs, it is better to add a fiberglass mesh in the space to be filled with concrete, as a reinforcement.

[@hififriend4512]

Thank you :) I've only used the smaller glass fibers. A major problem was that it took 2 weeks for the concrete to harden. When we removed it, it was still not hard enough in some places. And then the cracks formed. The next time I will build a bookshelf speaker and try out the fiber glass mesh.

[@Turkeydinner]

It won't stop cracking. It will only stop it from falling apart when it cracks.

[@PKWeaver74]

I'm no expert and haven't tried this myself, however my brother-in-law is a civil engineer who specialises in concrete corrosion (mainly bridges) and tells me one of the main factors that allows water into industrial concrete in the first place is the contractor has added more water to the mix than specified in order to make it easier to work with at the construction stage. Apparently concrete setting is a chemical reaction rather than the water 'drying out' and for optimal results requires an exact ratio of cement/ballast to water. I couldn't help but wonder whether your mix may have been too wet? I hope you don't give up, you showed great attention to detail constructing the mould, good luck in the future.

[@drutt1985]

I read on a forum (can't remember wich) to use plaster reinforced with somekind of fiber instead of concrete altogether. It doesent crack the same way concrete can do. Concrete speakers seem like a good idea, but it's heavy, and highly impractical to work with. I have seen beautiful concrete horn speakers tho maynly horns for mid and high frequency drivers. All materials have they pros and cons tho.

[@hififriend4512]

@@PKWeaver74 thank you for your comment. Next time I will probably try to build a bookshelf speaker, if something goes wrong it wouldn't be as bad😅. We also added a fluid which lowers the waters surface tension an therefore the concrete gets more liquid and easier to work with. It also reduces the amount of water you need, so maybe that's true what you're saying. Another problem might be, that it was very cold at that time of the year (we still had snow) and I left it to rest in the garage. Anyway thanks a lot for your help.

[@elmultimediaschoolofartscu3924]

Not fair. We did not see the end results 🤣🥺 not fair at all guys

[@jonayamaha3215]

hey man, i really like concrete speakers if you can afford the weight (i tend to move speakers around the house so weight for me is a no go), my cousin has a pre molded concrete factory, he says you could make 6 panels with a mesh inside and then assemble it like a wood speaker would be assembled (i'll add that you should use bracing, being concrete doesn't mean that it wouldn't resonate), i'll suscribe because i'm curious to see what project you do next. Greetings from Argentina.

[@hififriend4512]

Thank you for your nice comment :) If got a few projects down the line and will finish them soon. It's a lot of work tho. I really appreciate that you subscribed. Have a nice day

[@lotusmanb3832]

That mix is way to thick for this application.