In reply to my post:

Romy the Cat wrote:

The epoxy carbon-kevlar and glass fibers staffed with damping? I wonder how more fun would be if they staff these hollow horns with sand, I would…. I had once an idea to have a very soft sand horn using sand-filled air balloons as the horn walls….

 I got an email:

Dear Romy, why not simply use sand?? Have you been to a metal foundry? They make moulds of some resin impregnated sand. Just add a little extra resin, expoxy or something and it would be quite strong and have a surface...

I was thinking about it: what a phenomenal idea!!!

If you ask the folks who build sand sculptures:

http://www.harrisand.org/team_champion_photos.htm

… then they say that water hold sand together. If to substitute water with some kind of glue then it becomes a phenomenal opportunity for horn construction. It will be heavy, cheap, easily made by anyone, superbly damped, have necessary-rough surface. Just made the horn let the glue to solidify, cover the horn with some kind epoxy finish to protect the surface and the … fenita la comedia… The metal frames might be injected into the sand molds easily…

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.

Best regards,
Paul S

Romy the Cat wrote:

... a trip to a beach….

Everyone seems to be forgetting the difficult part of making any horn from a casting. It called a "mold". Making the mold is very time and labor consuming. Every time you want a different size, shape or flare rate you must build another mold. True, once the mold is made it is easier to cast a horn than machine one, but molds don't last forever either. If it was easy, then everyone else would be doing it.

Rgs, JLH

jessie.dazzle wrote:

I'd probably quit my day job if …. The much rumored new/old Vitavox drivers turn out to be good and available.

decoud wrote:

Yes, I should have said modular like your bass horns, but with much smaller segments, e.g. 36 segments of 10 degrees. Assuming one keeps the profile the same, the only difference between different sized horns is scale, so a single mould "capped" at variable lengths could be used to make a large range of horns. But I suppose it would not work if, like in your case, one needed to change the profile to suit other imperatives. (Though at 40Hz presumably one would have to start thinking about changing the house....)

Not to be pessimistic, but I have already visited this idea and it does not work. The problem with trying to “scale” sectioned panels is the amount of curvature in the panel sets the flare rate. Therefore, the flare rate is not “scalable”. The only way to change the flare rate is to change the number of sections. This in turn will change the angle of the mating surfaces along the edge. This then in turn requires a different mold for each flare rate. It is a no win situation.

Rgs, JLH