I am not ‘lucfm’ and I hope he will reply to you but I would like to pass some of my observation that you might find useful.
In my past when I discovered Fane Studio 8M I went over a number of 5-8 inches. At that time I used AG’s Trio upperbass horn and I was looking for something more interesting – the default AG’s bass driver was quite poor. I had very specific requirements to the driver and tried quite a few of them, predominately vintage drivers, as the today’s driver did not necessary comply with my prejudges about “proper cone structure” and “proper suspension”, not to mention their low sensitively and their aiming for the port-like exertion….
I hardly see how T/S characteristics affect the actual sound of a driver loaded in horn. People do modeling, circulations, spared to each other “smart” theories about the driver-enclosure interaction. I know all of it but I care less about it as I feel it in one way or other work for boxes but as soon you load the damn driver into a horn, them all the rules are off and only God knows how it will behave.
I mean - the behavior of the driver is still predictable IN TERM OF PRESSURE IT WILL DEVELOP but nothing know in term HOW it will Sound as soon the horn loads the driver. There are so many none algorithmable variables in horns, drivers and rooms that from my point of view as soon a diver hits belong 500Hz all calculation or theories should be tossed away and the channel should be actually heard and assessed with proper (objective) listening evaluation teachings.
So, why the upperbass driver in a horn does not comply with any theories we know. Now let go to the ugly part: I feel that the answer is because all our upper bass horns are eventually a half-ass crap by the nature of our design because we are greedy dudes….
Make an experiment, and I will simplify the case quite assertively. Take a typical compression driver, cross it at 800Hz, second order and load it into a proper contemporary horn (Tratrix or JMLC) of 300Hz. Listen that horn, you will get some sort of sound that let accept as OK Sound. Now begin to very slow lower the crossover point and keep listening the channel. While you lowering the crossover point, somewhere around 550Hz (I took this number purely arbitrarily as it would depends from VERY MANY circumstances) the horn will begin to demonstrate what I call “choked sound”. The “choked sound” is HOW HORNS SOUND IN 99% OF ALL HORN INSTALLATIONS OUT THERE – people just too damn to deal with it. The “choked sound” is the satiation when Sound produced by a driver can’t be “processed” by horn. In this “choked mode” a horn produces the “sonic boom” that was made by the horn’s bell and that “sonic boom” screw up the enter band-pass of the channel - the game is over. Increasing of the crossover point for ¼ octave (for instance) will fix the situation - so we have approximately one octave between horn’s rate and mix crossover point…
Now, apply the very same excrement to the upperbass horn. You spent a half of your vocation, pile of money, huge amount of useful livable space, gallons of blood and weeks of arguing with your homemates, your played the real-estate acrobatics to ingrate all installation and eventually you defeated everything and made your damn-proper, upperbass horn. You did not cheat and your made it with a proper small throat, perfect driver and a full-profile opening. Not you need to decide where to cross it. If to do it PROPERLY then you need to cross it at ~180Hz. You look at mirror and ask yourself: “I am out of my mind to make 600 pound 50-inch horn and to use it ONLY down to 180Hz!!!!????!!!??!?!?!?!?” Well, we all were there and we all know the answer: no, you will cross it much lower to get the “horn bass” under 100Hz. If you very smart then you even build a back chamber to get come bass boost hear the horn’s mouth rate. You are not a fool – you can recognize the signature of the “choking sound of the sonic boom” in your horn that I described above but you juts close your eyes to it and declare that it should be this way….
I can go on and on but you get the picture – our uperbass horns are conventionally are crap (I do not even mention the bass horns) and when we talk about the sound of one or other better drivers loaded upperbass horn we are talking about the sound of a given driver under the barbarian condition of the “choked sound”
Well, the described effect is not as horrible as I would like it to portray but the “choking sound” of out badly made horn installations should not be taken out of consideration.Rgs,
Romy the caT
"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche