For a vocal range horn, use the Delta 10 or JBL 10 inchers.

So I'd love to see an illustration of what you are talking about. At high frequencies where a boundary becomes a reflector, it would stand to reason that making the reflector so that the angle of reflection directs sound towards the mouth would be best if you wanted to promote HF energies. Or make the angles of reflection to direct sound into an absorbent material or device if you want to attenuate HF. Curved reflectors would seem to do a little bit of both, so I'm interested to see examples of what you're talking about.

Maybe you're talking about something like the diagram below?

Cant do much about the areas in the angled bit really, where length is above 40cm... but I think it'll be ok. It's a little more even than before.

I get 2.8m dead down the middle, probably like 2.9m considering the length is more towards the outter bits so I'm happy with that.

I remember seeing that diagram when I was in yr 8 or 9 highschool doing physics :P

At low frequencies, say 200 Hz or less where the wavelength is 5 feet long or more, the wave doesn't see the bend as an obstacle at all, so a reflector serves no purpose. Problems generally arise in typical cabinet sizes at 400 to 500 Hz, precisely where other designers have run into problems they've tried to cure with flat reflectors with varying degrees of success. Most have thrown up their hands in defeat when they couldn't get usably flat response above 500 Hz from folded horns, blaming their woes on the supposedly insurmountable 'mass rolloff' obstacle. This is really a cop out, as the Fhm calc has nothing to do with folded horns per se anyway, but if you tell a lie often enough sooner or later it takes on the ring of truth, right?

At high frequencies/short wavelengths where the bend is an obstacle you don't want to 'bounce' shorter wavelengths off reflectors, as your illustration shows. This is what Huygens postulated, and he was wrong. If you imagine the wavefront as a group of particles across the width of the pathway, rather than one particle as you show it, what happens after they bounce off a reflector is that they lose their cohesiveness as a wavefront, emerging at various angles of phase and cancelling each other out, killing HF response.

With rounded bends, specifically with large inner radii, the bend doesn't reflect at all, but instead serves as a true waveguide that allows the wave to pass through relatively intact, rather than being broken up. Again, I don't have an illustration of how it works, but Sheerin has some very good ones. Oddly enough, after he posted those at the AA forum, the outraged cries from one source in particular that my folded horns couldn't possibly work as advertised ceased.

Still waiting to hear from Ed Dell on the question of permission to reprint my articles, otherwise I'm ready to go on the site.

Wayne, I think you're referring to the pics on John's site that show waveforms passing through a 'square' bend off a flat reflector. Yes, the angle in equals the angle out- just like playing pool- but, if you trace the path of each of the point source particles that comprise the wave you'll see that once they reflect off the bend a large percentage of them will smack into other particles still on their way to the reflector, and those colliding particles would then take off helter-skelter every which way, rather than going towards the mouth in a cohesive fashion. This concept doesn't necessarily duplicate precisely what happens when a wave is fractured into smaller wavelets at various angles of phase, but it's pretty close and should be easy to visualize.

What I was referring to was a series of posts that Sheerin put on AA with sims of round bends, showing how they allow passage of a wavefront intact, without any reflection and thus fracturing of the wave into wavelets. This is one of his pictures, and it shows an entirely different scenario for passage of a wavefront as compared to a reflector. Assuming, that is, that I managed to get the URL right this time.

When wavelength is small in relation to duct size, propogation is more like this: