VintageTechnologies wrote:
Apart from the issue of correct theoretical construction, do you suppose a large enough horn finally reaches a point of diminishing returns or even regression?
Another fascinating question ! I would not pretend to know the answer but logic and instinct might suggest that, so long as the correct exponential or logarithmic curve (another complex debate on its own) is observed, the spherical wave front (in the case of a circular horn) will continue to expand ad infinitum but way beyond/beneath the hearing capability of the human ear. If the curve is correct, the quality of sound should not deteriorate but volume might, depending upon the driving force of the soundbox/reproducer design. Matching of components has been found to be relevant and important.
The largest
period horn I have listened to "in the flesh" is the Expert All Range which has a bell mouth diameter of 36 inches. It produces an impressive sound as does its slightly smaller cousin the EMG Oversize at 33 ½ inches. The output of both can be described as "holographic" but the expansion of each follows a slightly different exponential curve thus each sound is slightly different. The Expert also has fewer bends in the conduit. I have also heard both Nimbus horns, the first with a mouth diameter of some 40 inches (approx' 1 metre) and the second with an outlet of approximately 2 metres from memory ! The expansion rates of both the latter are very different compared with either EMG or Expert, thus the sound is also different again. Additionally, the largest Nimbus horn was driven by a parallel bore thin-wall (from memory) tonearm which, in my opinion, could be a mistake. Certainly, when the smaller Nimbus horn (now in my custody) was mated to an original cast brass EMG tonearm, the quality of sound output was pretty good. However, it always has to be borne in mind that the whole debate is very subjective and opinions will vary according to taste, age, musicality and hearing ability etc. Personally, I was not over impressed by the performance of the 2 metre horn, the sound from which had to be augmented with modern loudspeakers at a public concert.
For me, a horn (and the necessary system that goes with it) has to project the somewhat indefinable "holographic" effect of giving the illusion that the performers and/or instruments are actually in the same room as the listener. This seems to define the real "magic"---for it is such---of what it is all about.