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jessie.dazzle wrote:

After observing a pair of AK151s operating in free air, though only lightly driven, I just don't see how they can possibly generate so much pressure, as the cone barely moves!

Why shout they move? One of the idea of using horn is minimize excursion of the diaphragm and let it do not move a lot. Still it might be possible le that this Vitavox will not be the best chose for your horn, with LF horns you never know. It all depends what kind horn you will be making and how are you planning to use it. Even then Sound of this thing might not be predicted and should be observed after everything is gone….
 

jessie.dazzle wrote:

As for geometry of the bass horn, I am not yet at the point of needing to define the curve ... I have smaller horns to build first. But in order to plan for room placement, and physical relationship with the smaller horns, at this point my main concern on the bass horn is the central axis; Option "J" : Straight (vertical) for most of the length, curving 90° before the mouth. Option "C" : One big continuous curve (a sort of mega "Horn of Plenty"). As the C curve has a less sharp bend, that to me seems the better choice... but it does take more space.

I think J-horn is more practical as it has smaller footprint. It looks like one single J0curve does not create a lot of problems sonically. Still you are entering a railm where no one can say anything defiantly. Sill if I had space I would go for a straight horn. If your real-estate can afford C-horn then you can afford a straight horn…

jessie.dazzle wrote:

Low Pass Filtering : I am certainly ignorant here (an advantage when undertaking major projects... otherwise I probably would not be attempting any of this), as I don't see the problem... I had simply planned to use a large induction coil with each AK151. ???

Yesm I know but there is a catch in there. Those drivers: 515G, AK151, AK15/40, D130 and alike do reproduce some HF over 300Hz. The problem that it is not good sounding HF and it might screw up your lover MF solution. So, to resolve it you might need to go for second order. Religiously speaking the second order is not good but it might be the only solution. If you go for smaller drivers size (10”, 12” or 14”) then the problem would be even more. If your horn was 40Hz horn and you would like to kill it at 120Hz then you need even sharper slope. Once again you need to put this thing in use in order to say anything. It is possible that some drivers, in some application might be working fine “together”, handling the same frequency range with both channels. I have seen those satiations and did use them myself.

jessie.dazzle wrote:

Time delay : Um yes... This to me seems the most threatening issue... But as I mentioned, these horns will be on wheels, free to move independently of the other horns. However, my room may not be large enough to accommodate the necessary staggering. This could lead to a near-field listening situation that would be out of scale with the horns.

Welcome to the club. In the near-field environment the time dealt from 10” horn is a mortal issue. People out there use digital time delays for the rest spectrum and try to convince themselves that it sounds acceptable. I despise those efforts and generally do not even go to listing horns with digital delays (uselessly they use digital crossovers as well). My observation is that those horn installations with digital delays/crossovers sound extremely poor. I know, I know there is an army of D-horn people that disagree with me but I feel that they hardly know what they talk/hear… There is another option. Last year, or even before, when I was bitching to Dima about the very same subject he proposed a time delay processor that would do the delay “differently”. He meant to do it without digitalizing of sound, using modulation and de-modulation, storing the UHF signal at temporary memory. The idea looks very-very promising and Dima proposed to make a prototype to try it’s transparency.  At this point I do not know how acceptable it might be. If it was then the FM delay processor might be available from Dima.

jessie.dazzle wrote:

Which could in turn lead to me looking for another house.

Here we do… Still, even with a large room 10” is hardly manageable. Let pretend that your horn has 60” by 70” mouth. With 10ms delay and J-horn you would need to position the J-horn way ahead of your MF/HF horns but with suck a large mouth you would find yourself on deep reflections. Long time ago I come up with a scenario how I would like to do it if I go for 50Hz straight horn but I have no real estate for it. Here is how I thought to make it:

Until I have the correct room my drivers sit in my storage….

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