Why such a low compression ratio? Not a good idea IMO. Compression ratio is basically where most of a compression driver/waveguides improved efficiency comes from. Its that efficiency that is the attraction (that and directivity control of course). Basically with CD you need all the efficiency that you can get at the top end. In my speakers the DE250 is running unattenuated at 10 kHz. Lowering the compression drivers efficiency would require the whole system efficiency be lowered. And for what gain? Lower distortion? Not a good trade off since distortion in a compression driver was shown not to be a subjective factor (see my AES paper on this).
I have no drawings of the DE250. I will try to find them, but maybe Dr Geddes can help with this, as believe he worked as a consultant for B&C and still has good contacts with them.
Some info can be found here:
Red Spade Audio: B&C DE250 1" compression driver - looking inside
Red Spade Audio: B&C DE250 1" compression driver - looking inside
Any picture of K1132? Braces - phase plug is brittle (nothing decisive).
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Sadly I don't have any pictures, but one difference I see is the K1132 phase plug is shallower on the edges, and was designed for a 2" throat. Basically more the shape of an american football when viewed from the side. I do know the designer was treating the area expansion inside the phase plug as part of the horn, but the overall concept is very similar.
My only thoughts with the braces were in consideration to staggering them between rings (which I think the K1132 does), or perhaps looking at the interaction into a rectangular horn to see if there might be any potential advantages there.
