My method for a quick single or pair is to build rectangular. You can build a horn like this in a very long weekend if all the steps have been carefully planned...
but how to cut that complex curve that is the intersection of the curved wall and the straight wall??? extremely difficult to plot... and even if we can plot it, how many of us have a large CNC 3D router?
so I cut the straight side walls out of 3/4" plywood or even doubled up to 1.5", depending on panel width... I then screw in a brace that is right down the middle... this is easy to plot as it is just the center axis of the horn expansion... you can remove the brace later or keep it in if you want.. your choice..
when you drop a yardstick/meterstick across the face you will instantly see the complex curve... how will you ever get a piece of bending ply to fit properly on that uneven surface? simple. make it flat...
I do this with a "contraption"... that is southern for homebrew tooling... jig... doohickey-thingamajig... whatever... belt sander screwed and clamped to scrap wood... pictures tell it all...
brace in place:
contraption:
I clamped and screwed the sander to a piece of wood:
The actual setup for sanding.. you want this horizontal as your arms will be tired:
check your progress with that meterstick:
not quite:
yep, got it:
close enough.. remember that on a midbass horn, a cm or inch of error is lost to the wavelengths in use... do not go crazy with trying to keep extreme accuracy... quality of build is much more important! stiffen... listen... damp lightly... brace... lacquer... love.. listen... that is how you make great midbass horns.. and do not be afraid to say "that sounds terrible" if it does.. that is only motivation to make it better...
adding layers in the next installment.... i tried to start and finish on Father's Day weekend... I lost... so maybe one late night this week...
Peace,
Me
Posts
thank you... would love to see the next steps as it progresses... have thought about how something like this would go together but could not wrap my head around it..
ReplyDeletecheers,
matt