@erik_squires wrote:
- You can’t get high output AND low distortion without a midrange driver.
This rings true with direct radiating dome tweeters in 2-way designs, but when you load a fitting, relatively low fs down tweeter with an 8-10" waveguide you can lower the crossover to below 1kHz and have rather flat power response at the crossover, while also relieving the dome tweeter in its lower band (even crossed that low) to such an extent, that the real limitation in output is more likely to be the woofer/midrange driver (example: S.P. Technology’s Revelation speakers (sadly discontinued) sports a ~10" waveguide on a 1" dome tweeter and two 8" SEAS woofer/mids in a d’appolito configuration, and they’re true full-range speakers down 20Hz. They might be a standout, but nonetheless they’re 2-way, full-range and no less SPL capable than many comparably sized 3-way designs).
Another advantage here is that neither an 8, 10 or even 12" woofer/mid would see no significant beaming issues crossed below 1kHz. With a curved waveguide profile (to save diameter size) that doesn’t amplify linearly it does typically equate into a more complex crossover design (active config. would come in handy here), but if size isn’t an issue you can have yourself a fairly straightforward approach.
Horn-loading a compression driver makes for an even more powerful combo compared to using a dome tweeter, and maintaining a 2-way design becomes a matter of finding the proper balance combining lower range energy at a given crossover point with upper end extension. Using a 4" diameter compression driver - while having excellent lower range output in a fitting horn and very low distortion numbers even at prodigious SPL’s - will be a challenge above ~10-15kHz, but with a proper motor structure in particular can alleviate severe drop-offs here.
Myself I find crossing 15" woofer/mids in the 600Hz range to large format constant directivity MF/HF horns to be very well sounding, and the dispersion pattern match at the crossover between the woofers and horn is excellent. The EV compression driver sports a 3" titanium diaphragm with a pre-fitted 1.4 to 2" exit snout adapter. Flux density sits a 2.1 Tesla, so a large horn is necessitated to properly load such a powerful driver. In any case this combo handily combines very high output with very low distortion - even more readily so with the main 15" woofers high-passed above 80Hz, but that’s trivial in this particular context.
Also worth mentioning here is the advantage of having a single point source from ~600Hz on up, and thus while augmenting with subs for an effective 3-way design for all intents and purposes what’s at hand is 2-way.