Building Buschhorn MKII for 12 CM driver

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Thanks Holdent, can you reassure me that the only differences between the fist plan and the revised plans are the extended speaker board and the rear diffuser ?
would the slightly different construction at the rear of the compression chamber make much difference ? (its just boxing in the step that was on the original plans)
 
Regarding the differences in Ron's plans; if you can make out the numbers in the revised drawing you'll see that the radii of the turns and the lengths are just a wee bit different. I'm building off the A126 (last modified iteration). I am constructing the "rear diffuser" to be adjustible. By modifying the interior horn sections and building a rectangular box I was able to make the CC adjustable in volume with a finished cab. I wish my photographer (read daughter) didn't have such a busy social life, I could post a pic.;) Ron suggested to get a full size plan for the construction but I do not have access to that. The differences in the "last iteration" and the modified are actually fairly negliginle, IMO. The use of a 12+" baffle is the trade off for larger CC size.
 
First a "re-look" at the MKII:
I have had a chance now to look in much greater detail at the MK II horn shape. Its not linear, is not conical, and seems closest to some kind of hyperbolic-exponential expansion with an expansion rate of much less than 1. Frankly I can't figure it out so I can't reliably model it. Thus, the earlier simulations I posted may be way off.

Next the A126:
I agree with Westend -- there were modifications from the original bitmap drawing of Ron's initial design that appear to small changes in the lengths and widths of the sections. The design evolved as Ron fine-tuned it. I believe that the drawings are all dated on the right-hand side -- you should be able to start with the newest and work on back.

Not surprisingly, I agree with Westend's decision to change the design to make it easy to modify the CC volume! I be very interested to see what was done.
 
Chrisb and Planet 10 have some pics in the Fullrange driver forum of how they modified the CC size in the A126. I chose the adjustable route to accomodate a driver upgrade or replacement as well as tuning the CC size to the Fostex 126e. WRT Buschhorn MKII, I would maybe add some height to the overall enclosure to accomodate the bigger driver and to gain volume in the compression chamber. Since the MKII is built with such a long CC I would think that would be fairly forgiving in modifying the volume. Dr. Busch posted on the German audio forums that the CC size of both the MKI and MKII should be increased, especially, to handle the newer drivers.
 
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