This link suggests using the Dayton ND20FB in a simple horn loaded configuration that allows a crossover point of 1.3kHz w/ a horn a little over 3" wide. That calculates to almost 10" CTC spacing for the mids I believe. (start reading about 1/2 way down):

http://www.diyaudio.com/forums/showthread/t-101908.html

I don't know much about horn theory or application but it seems like a good idea unless something obvious is being overlooked. My questions would be along the lines of how the horn loading effects the raw driver specs such as Fs, distortion, and power handling. The raw driver Fs 1,700 Hz.

This link is also provided in the info above but it sums everything up nicely:

http://www.diyaudio.com/forums/attachment.php?postid=1194160&stamp=1177617133

With the current sale price of $4 a piece for the ND20FB-4 the price works out to about $31/foot. The ND20 tweeters already have the reputation of being an excellent performer for the money:

Let me know what you think.

Thanks,
Aaron

• ND20FB-4

Additionally you have to use the "A" model not the "B" model since you won't get the proper c-to-c distance without cutting the flange almost to the start of the fabric dome itself. If you cross at 2500hz, and you cut the flanges then you can put off comb filter distortion to around an inaudible 15,000 hz.

But if you use the 3/4 inch domes, then you have to use a three way system, and you can't use a mid range with a c-to-c exceeding about 5.25 inches.

Personally, I prefer the dome sound to the alternatives. However, you have to be much more careful in your design if you use them, and you will have to add a large woofer to each side to cover the bass since the small speakers you might use for mid-ranges will not go low enough.

See the pictures of my system below.

Other people may have other solutions.

Marlboro

• Marlboro's Calipso Speaker system

Dayton PT2C ~ $35 in bulk. I think you can get it closer to $30
if you call and place a larger order.

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=275-085&ctab=10

This is about $60 per foot, double the price of the small domes,
but there is less drama.