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jessie.dazzle wrote:

Resonant frequency  : I did not try to measure it. Can anyone confirm the following : I assume this parameter is most easily determined by playing a series of tones at constant signal strength (volume setting) while measuring the SPL; the frequency of a tone that gives the highest SPL is the resonant frequency of the assembly. Is this correct?

Well, it is a bit incorrect way to determine resonant frequency as it will be “colored” but other factors.  The easiest way to get the resonant frequency very accurate and very prices of connect resistor of a few Ohm   in series to a mounted driver and to drive the driver with generator, sliding frequency up and down, measuring the highest voltage rise on the resistor. It will be very prices as the peak will be very sharp. Now, it is simple to move resonant frequency up and down but to associate the moving consequences with subjective sonic results is way more complicated as it will greatly depending from the positioning of you horn, filters and many other things.

jessie.dazzle wrote:

Filters :  Initially I ran the horn full range, without the other horns. I was immediately sort of horrified at how high (in frequency) it would play. I then stuck a 5mH coil in front of it, so as to low pass somewhere around 200Hz (really could have used a 3.5mH coil, but didn't have one on hand). Next I made a band pass filter to give a theoretical operating range between 90 and 185 (normally I'd let it go higher, to around 250Hz but again, I didn't have exactly the right stuff sitting on the shelf... Used a 150µF cap followed by a 10mH coil; driver measures around 6 Ohms). In case its not clear, the filter is first order. So now with things reined in a bit, I sat down to listen, both with and without the other horns.

I think you will eventually end up with second order filter, consider the rest of your system. BTW, for this particular midbass channel if you stay with speaker-lever filter you might have inner-debate what to chose – the use of lowest possible series DCR or use air-core coil. Both are great but they are mutually excessive.  I went both ways: had high inductance air-core coils with 8ga wire and have some metal-core low DCR coils. My vote goes for lowest DCR and huge air-core coils with ultra high sensitively spacers is in a way a recipe for various problems.  In my time, when I was experimenting with speaker level filters (before the DSETs), I paid a LOT of money for custom-made low DCR C-Core toroidal Inductors. Nowadays they are available and none expensive:

http://www.parts-express.com/14-gauge-c-core-toroidal-inductors.cfm

jessie.dazzle wrote:

Sound :  First, I may be totally off here, as I was extrapolating potential from a situation where the horn was about 15 ft out in front of the other horns, so any evaluation in the context of the rest of the system is to be taken lightly. Given that disclaimer, I will say that I was satisfied in a very basic way. This may seem obvious; I sought first to confirm the presence of real mid-bass as compared to what happens when filling in for the absence of this horn as I had been doing, by running the other channels beyond their ideal range (running the 115Hz horns down lower than they should go, while running the lower bass enclosures up higher than they should go... For this session, I did go to the trouble of changing the filters on those channels, moving their operating ranges out of mid-bass territory). Well so do I now have real mid-bass? At this point I can only say that this bass differs in that it is not as constrained sounding, but more weightless and relaxed... Somewhat a contrast to the way the horn looks. Next I would say that despite being way out in front, in the context of the rest of the system, the sound of the additional channel did not call attention to itself; my neighbor however, listening from his apartment, did ask if I hadn't changed something... To me, the system did not seem any louder. Removing the horn from the system (to make space for creation of the second one) turned out to be difficult, and not just because of its mass; given the horn's position, I know how silly this will seem, but momentarily disconnecting the channel had already confirmed that its contribution would be missed; the result was that it stayed there for about a week. I will post more observations once I get the pair of them up and running.

You might want to get yours a test crossover to found a good configuration between midbass upper knee and upperbass lower knee. I might be complicated each time take the turns from coils or to solder caps. You might rent in your local pro shop for a weekend some kind of digital crossover or but it for 100 used.  You will not get good sound from it but you will have a good modeling tool. With some experience you will be able to prototype the results. It might be a bit tricky as low-path at line level and low-path at speaker level always sound and act slightly different, so it needed some time to learn and use to the difference. Still, the test crossover is a good tool to see if you move to the right direction…

jessie.dazzle wrote:

Weight : One horn without driver, rear chamber or supporting chassis and wheels weighs around 900 lbs. Heavy yes, but not excessive; with music playing at live listening levels, one's hand is enough to detect whether or not the horn is working. The assembly comes apart in quarters split along the horn's firing axis (see clamped flanges in photos above). A single multi-layer lamination (about 1" thick) over the forming tool or buck yields one pair of mirrored quarters, or half a horn. I will post photos of the construction process some time in the future.

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