Here's a versatile high sensitivity design. It works with either the Eminence DeltaLite 2512 or the Eminence Delta 12A, and can use DE250 driver or either of Erich's "clones". You can put together a remarkably high end speaker for pretty cheap. You WILL want a subwoofer with this, though (like all non-huge high sensitivity designs).
Measurements here are with the 2512, at about a meter, indoors, on the tweeter axis, 1/6th octave smoothed. Woofer and waveguide are on the same mounting plane, so if you inset one very much, inset the other by about the same amount (or you can vary the insets to direct the vertical lobe a little).
BTW, on these type designs I'd recommend getting the tweeters up away from furniture height for use, to minimize near reflections off of it all -- sounds better, I set mine at ear level.
And if you aren't going to toe them in, then you probably are better off NOT making a controlled directivity waveguide speaker. Without toe-in the sweet spot will be narrower
than with an omnidirectional or wide dispersion design; with toe-in toward a point in front of the center listener, sweet spot will be much wider than with other type designs. Some time I'll write up a diatribe with circles and errors showing why that is. Anyway, if someone tells you they've heard an Ewave type speaker set, but they weren't toed-in.... then they didn't hear an Ewave type speaker set!
This version uses relatively simple crossover for me (though it has my finicky tweaks on the waveguide). Parts Express part numbers are shown on the schematic as well.
For the 33uF capacitor, an inexpensive NP electrolytic will work fine, but if you plan to have the speaker passed down through generations of your descendents, you can use the $13 film cap instead. Use film type caps for the rest (polypropylene or Mylar/Polyester) since the values are somewhat critical.
Horizontal Curves, 0 to 90 degrees in 7.5 degree steps:
The dark blue trace (the 7th trace) is 45 degrees.
Horizontal Polar Map:
As Erich mentioned, the woofer hole was cut too low, so CTC is about an inch and half further than it has to be. Anyway, here are Vertical (Up) curves to 30degrees. Flat response is a bit narrow in the vertical, but that should be better when the drivers are moved closer together.
Here is the on-axis response comparison using Eminence DeltaLite 2512 (red) and Eminence Delta12A (black):