what difference do curved sections make on a horn

There seems to be a lot of variation in horn designs in regards to whether curves or straight edges are used.

i.e.

Scoop bin vs Hog Scoop

HD15 vs other kicks

Funktion one/ turbo vs Xtro tops. 

Any insights on this ? It seems that angled mouths shorten the path length while curved edges make the transition from the throats compression smoother.   My take on this is it is frequency  sensitive ?

i.e Looking more at the top horn designs care seems to be taken on making the design smooth at the throat, while the exit can be angled, perhaps shortening the path length there decreases back pressure from those crucial high frequencies which are shorter wavelength than these angles.  The F1 phase plug is smooth from behind if taken out, as high frequencies are most sensitive to perturbations while compressed in that slot.

In the scoops or HD15 the smoothing of the horn occurs later in the longest section, where the wavelength could interfere ?

Does that kind of summarize why angles or curves are used in specific areas ? 

burningbush wrote: With subs, I should imagine that the wavelengths we are dealing with render the small differences between curved and segmented as not relevent.  At higher frequencies I think it has a great deal of effect to dispersion.  I am sure somebody more knowedgable will fill in the details...

I am guessing but the the angles in the F1 horn serve to shorten the path length, so when sound exits the horn it just shoots of a couple of sides and out, where as a curved exit may be relatively slower in that regard anyway.   I was reading abridged interpretation of an old paper on compression drivers where the horn flare has to facilitate a fast wave exit as high frequencies can are prone to back propagation into the horn. I think thats what they were trying to say.

So basically it seems like this  inversion of principle.

Low frequency horn : sharp angles at throat = faster attack, smooth exit = reduces phase problems, chuffing etc.. 

Hi frequency horn: smooth at throat = reduced phase problems,  sharp at exit = faster wave exit.

Curved (often exponential) horns give the best loading to the driver, but aren't very useful in terms of pattern control as the higher frequencies tend to beam. A straight sided horn will give a more constant pattern, but can suffer from reflections at the mouth causing uneven frequency response (horn honk). A good compromise (for mid/high) is to use curves for the throat, straight sided middle section, and either a curve or a larger angle straight side for the mouth to improve termination.

As burningbush said, it is relative to wavelength. For bass/low mid there will be very little difference between a curve compared to a series of straight sided sections which approximate the curve.

That's my opinion of it, here is the work of someone more learn'd

http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(1975-05%20AES%20Preprint)%20-%20Whats%20So%20Sacred%20Exp%20Horns.pdf