I started making three "real" SynergyDIY horns, and redid the spreadsheet for a more efficient (and neater-looking) shape. This spreadsheet is for a horn in which the inside of the "mouth" extends all the way out to the full height and width, without the useless outer lip. Like this sketch:
Here's the link to the new spreadsheet: http://www.libinst.com/SynergyDIY/V3/Synergy%20Calc%20v3.xls
BTW, I downloaded the free open-source spreadsheet program "GNUmeric" and my horn spreadsheet opens just fine in it! So, if you don't have Excel, no worry, just download and use GNUmeric for free: http://people.gnome.org/~mortenw/gnumeric/gnumeric-1.10.16-20110616.exe
And now, for some pictures of the build, to try to coax you into trying it (if I can make them, you can. I'm an abysmal cabinetmaker with cheap tools!).
After cutting the boards to their outside dimensions and angle cutting the ends, ready for the marking up with guide lines for making the slanted cuts. The beer bottle is an essential tool for this part:
A view of a "sled" jig for making compound angle cuts. Just a board, something to guide it on, and some clamps to hold the work down in the proper place. Pre-cut the jig board, then line up your work board to the cut edge, run it through again. You get perfect cuts without a sweat or much cost. Harbor Freight has the clamps for about $5.
Some will have to be done with a vertical sled jig, just butt two boards together to make a sled that holds the work perpendicular to the saw table.
After those are all done, more guide lines to figure where any offset drivers (midranges, woofers if you're going 3-way) go:
For the first expansion "throat" section, I used wood screws to dry fit the pieces together, and then to hold he pieces while the glue dried. Get the pieces lined up right on the outside edge, it will make for less filing and sanding later (I wish I had on this first horn, but it still wasn't hard to clean up).
To attach the "mouth" pieces, I couldn't get screws to attach things right, too hard to position while drilling or putting in the screws. In the end, I just used good old duct tape to hold stuff till it dried. It actually worked, though a more elegant solution would be nice....
Here's how you'd like the outer corners to look (sorry for the out of focus shot). My other 3 corners weren't so tight right away, but are close enough. (Edit: not a great photo -- the "mouth" of the horn is upwards, thats the other side of the open mouth you see across the top...)
Here is the front view, before any filing, sanding, or filling. Came out reasonably decent, and verifies the spreadsheet calculations:
I had to jump ahead and see what it was going to look like with all the drivers glommed onto it:
The midranges will have back chambers (mailing tube sections) and the woofers will work into a box for bass. According to HornResponse, it should work (the horn of course won't load the woofers at bass frequencies, but I'll get all the drivers playing from the same acoustic center -- a point source.
Here's a view of the other side, without drivers yet, showing the tapered port holes for the midranges and woofers. I may still need to put in plugs to fill in the midrange and woofer cone volumes, will see how this works first.
I'm writing this up while glue dries on the tweeter mounting board. I'll update when I can get drivers really mounted and can make some measurements. I still have some work in store to figure out how to mount "super driver" into an enclosure (planning on a tower type for the L and R, a long horizontal box for center channel).
The dimensions of this horn, BTW, are 24"W x 15.3" high.