Charlie:

That's right.

Let's say you have a preamp/power amp chain that puts out, say 5 millivolts of noise constantly. Hang a direct radiator speaker on it that has a 90db efficiency for 1 watt input. It will produce that 5 millivolts of noise from upstream at a sound pressure level of "X". Hang a horn that has an efficiency of 106db for that same watt on it, and it will reproduce that same 5 millivolts of noise a whopping 16db louder.

This also explains why horns sound better with tube power amps. Any crossover distortion, or any other nasties such as the effect of large amounts of negative feedback from the power amp get amplified much more with horns. Tube amps run much 'richer' in class A/B than solid state ones, and also have much less global negative feedback. For my tweeter horns (1,200Hz and above) I've even gone the route of class "A" triode power; no crossover distrotion, and no negative feedback. Of course, you could also use a class "A" solid state power amp, but those are very, very difficult to come by.

[This message has been edited by soundhound (edited November 25, 2002).]