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In the Forum: Horn-Loaded Speakers
In the Thread: The absolutely “best” material for horns construction.
Post Subject: Structural flaws with polymer concrete when dealing with large and complex shapes; stress fractures and reinforcementPosted by Monette on: 5/25/2022
"Other uses for polymer concrete have spun out of its use for counter tops, which can be large enough that cracking becomes an issue. Hearths, sinks and even Roman style tubs have been constructed of this material. Variations in the aggregates, reinforcements and polymers have resulted in a fairly stable material that might also be used for speaker enclosues, and mold shapes keep getting more elaborate. There is no doubt that this stuff could be used for horns to good effect, and some aggregates treated right might yield surfaces that required mimimal further finishing. At the same time, it is possible to build up this material, so fine tuning - in the + direction at least - would likely be pretty easy. Grinding it is possible, too, but not so simple. Shrinkage of modern polymer concrete is minimal to negligible. Lightweight aggregates are also in widespread use, along with ground glass and other materials chosen to enhance finished appearance."
It might work to have polymer concrete base with something along the lines of a shaped metal reinforcing or perhaps a composite materiel outer shell. Perhaps after the concrete has cured a layer of fiberglass or CFRP could be layered over it, using the inner mold of the concrete as a structural support, during the vacuum bag and autoclave process. It would leave the internal finish and all the desired properties of the concrete while maintaining a light weight but strong supporting shell. There are some self curing reinforced composites that could make it easier to produce as well. This would also have the advantage of allowing the actual concrete section to be overall lighter as it wouldn't need to be so thick to support its own weight, which would improve the lives of speaker designers more than anything as the horns would be easier to mount. It would add difficulty to the manufacturing but might be worth it.
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