GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.

Post Subject: Nude Descending a StaircasePosted by Paul S on: 6/25/2010

Romy, Looking at your cartoon again, I wonder if you are showing manufactured trusses inside the horns?

If not, what does the shading that looks like trusses mean to show?

If so, your carpenters are either very good, very optimistic or very hungry.

Are you currently planning to do two curves per horn, or are you down to one?

If the "bottom" side that sits flat down on (or under) the existing ceiling joists/lower truss cords is more or less "triangular" in shape, then the "pitch" of the "sloped" side will change from the mouth to the throat, and the slope will not follow existing framing, apart from, perhaps, the mouth of the horn. If you plan a curve along the hypotenuse of the triangle, then the sloped side will also be a twisting curve, and I doubt it could be done with 3/4" birch ply, unless in many jagged "steps", like Duchamp's "Nude Descending a Staircase".

Unless your house is very old, the framing members are probably 12", 16" or 24" o.c., and most sheet goods for building reflect these standards. This might or might not be a consideration if you built a separate frame to receive the ply, where one might start with supports running nominally perpendicular to the joists and rafters and then add any necessary backing wherever it needed to be to reduce waste.

By far the the most dense birch ply I am aware of comes from Finland. It is resin impregnated, very very solid and strong, and it comes in MANY sizes. It is used primarily for production concrete forming. I don't know what it costs from a lumber yard these days (a lot...). Big commercial and industrial builders used to "yard-up" on this stuff when it was "cheap", and you might be able to find some someone who's slowed down and wants to get rid of some. Or, some might be available to scrounge from used forms.

Apart from the usual lumber "dealers", there are lumber "brokers". Normally, they would not talk to you; but these days, who knows. The big builders who "yard-up" on stuff like this often buy through the brokers...

Best regards,
Paul S

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