Unsound wrote:
"Macrojack, why would 'Horns have a greater potential than any other approach.'"?
Well I'm not Macrojack, but I did stay at a Holiday Inn last night...
Okay, my design experience is limited to systems that use a direct radiator woofer and a constant-directivity-horn (or waveguide)-loaded compression driver. Focusing on the horn section, here are a couple of inherent advantages as I see them:
1) Well-controlled radiation pattern, which results in a reverberant soundfield that has very nearly the same spectral balance as the first-arrival sound. Not all horns do this, but constant-directivity ones have this potential assuming you get a few other things right. Live sound sources usually result in very little spectral discrepancy between the first-arrival and reverberant energy, but most speakers fail to preserve this relationship. I think it matters because, in most listening situations, most of the energy that reaches our ears is reverberant energy.
2) Presevation of dynamic contrast due to negligible thermal compression at normal in-home listening levels. This can actually be detrimental if the horn is not paired up with a woofer that has similar characteristics; if the woofer compresses and the horn doesn't, then the system sounds brighter and brighter as the volume level goes up. But when the dynamic contrast in the recording is properly preserved (including correct tonal balance regardless of loudness level), the emotion that the musicians intended is more effectively conveyed because musicians often use dynamic rise and fall to convey emotion.
Disadvantages include:
1) Coloration. This is a complex subject, and briefly all horns produce coloration of some type, but not all horns are equally objectionable in this regard, and some types of coloration can be dealt with in the crossover. The best horns minimize those colorations that cannot be readily addressed by the crossover, and then the crossover does the rest. Unfortunately reduction of coloration to negligible levels by a properly designed and implemented horn cannot be proven in an internet forum post, so this subject is hotly debated. My comment here would be, just as not all cones or domes or ribbons are created equal, so too not all horns are created equal.
2. Challenging crossover design. With rare exception, horns call for fairly complex crossovers in order to minimize their colorations and provide a smooth transition to the woofer section. Those few horns that are exceptions are not constant-directivity types, and thus do not have the reverberant-field characteristics that matter in my opinion. Some people hold that complex crossovers in and of themselves are bad, and this I disagree with; as long as the crossover does its job unobtrusively, the component count has no audible consequence.
If horn colorations can be reduced below the audibility threshold, and if dynamic contrast and the reverberant field really do matter, then a good horn system offers worthwhile advantages over a conventional system. I think the colorations can be rendered insignificant with proper system and crossover design, to the point where a good horn system is quite competitive with conventional systems in the same price range. But I think one has to start with a very good horn to begin with, as most horns have audible problems that cannot be solved by the crossover.
In general smaller horn systems need less distance to "focus" than larger ones do; one of my customers was listening to one of my systems (10" woofer + 10" round waveguide) at slightly more than arm's length, with (to my surprise) no audible problems.
Now it might be possible for a conventional speaker to match the thermal compression charactics of a good horn system, but at a higher price. And I do not know of any low-cost techniques of radiation pattern control that are as precise as what a well-designed horn or waveguide can offer in this regard. That being said, I think a good planar system that inherently has good radiation pattern uniformity can also be pretty spectacular, but that's a different topic for a different thread.
Duke