I don't disagree with you on this one. A horn 'can' indeed disappear. I was specifically referring to a small directivity horn.I disagree. Good horn system can "disappear" like any omnidirectional. Problem with horn system is that
Firstly, most of them have horn only in upper midrange and treble section. Below that frequency it is a normal box speaker, so if diffraction can not be controlled well then the "disappear" quality is lost.
Secondly, if the horn is big enough to cover midrange frequency as well (from 800-1kHz up) then the c-t-c between horn and woofer is big and will need a long minimum distance so that the sound of horn and woofer can blend together, unless it is a big MEH (multi entry horn). If listener is at too close position, the "disappear" quality can not exist.
Cheers!