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serenechaos wrote:

"I think the ultimate length of the upperbass horn is 3”- 4” throat. With longer horn it would be very complicated to time-align it as the horn will mask out the MF driver."  Is this also why you use tractrix curve for expansion?  To shorten the horn, and keep the centerlines of all horns closer together, instead of exponential?  Is this a guess (length), or have you actually tried both curves, in this frequency range?

The type of curve used for upperbass horn is slightly different subject the slower rate the more bass extension you get but also your horn become longer. With faster opening you have less low end but in some way better quality of the lower end you get. There is no rule there but I feel that approximately 120-150 Hz is the region where the profile makes sense (deepens how you upperbass MacroImbeded in your room) to switch from fact opening (Tratrix, LeCleach) to slow opening (exponential, parabolic). The problem with 80-120Hz parabolic for instance is the size and vignetteing of MF channels in nearfield.

serenechaos wrote:

Where did you come up with these numbers for an "ultimate driver" from?

I presume you meant the "ultimate throat  size" not the "ultimate driver". The answer would be:  Practice of listening, thinking and experimenting with different solution. Do not make a mistake confusing the upperbass horns with midbass horns – they are different animals. For an upperbass horn (70-120Hz mouth) 3”- 4” throat is, all thing considered, is perfect in my view. For an upperbass horn (45-70Hz mouth) I feel a throat of 5”- 8” will be more appropriate.  Sure the people who use a single horn-loaded Lowther, driving with it full range will be laughing. Welcome to my world.

serenechaos wrote:

I don't mind building several horns, and drivers to experiment, but I'm trying to ask as many questions as possible first, to shorten the learning curve.  I've been digging for patents/white papers, and through physics and acoustics texts, but haven't turned up enough to actually base anything off of without a LOT of experimentation, or outright copying.

Robert, unfortunately the “patents/white papers, and through physics and acoustics texts”, equally to pontification of classically trained acoustic systems boulders have absolutely nothing to do with sound you will be getting from horn sand 99% of BS written about hors is juts worthless garbage. I know it sound like my personal attitude but it will take for you a looooong time to appreciate what I am trying to say. If you do not believe me then I would let you know that what I said is actually the private quote from a person why from my point of view know more about horn sound more than any other living person. I do not try to convince you or encourage you to embrace a specific point of view. All that I ask you is that what you found a source that from your point of view construct up a presumptive theory how to get Sound form horns then let me know.

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