Originally Posted by mwmkravchenko
What happened to 6?
Version 6 I'm holding. It is pretty much v7, only it is still in the old format. I'm holding it should this one not go over well. It also only has the PAR, and EXP math. It took me a bit longer to get the right CON outputs.
Originally Posted by maxmercy
Isn't a rectangular cross-sectioned segment of horn with two parallel sides best modeled as PAR vs CON? I have not thought the math through, but I thought this was why McBean added the PAR profile in the first place...
PAR is the best choice for some, but not all. If you are doing a single flare horn, and are only building with a single rise/run then it is best.
It's all about how close the total volume in the sections are in reality, to what you are modeling.
Here is a demo with a super curved target horn, to make things stand out better. This is what we are after.
OK, now let model it with a single flare rate with CON, and PAR. Then export the horn, and draw it up in a 3D program of some sort, and compare to the original. PAR-black, CON-green
Both leave a lot to be desired, and they will both contain a pretty different volume. If you used the CON(or EXP) flare here you will not get what you simed exactly.
OK, lets go with two flare rates. This is what most HR sims really are. The small changes at the throat some use are a drop in the bucket really. My spreadsheet four section TH defaults are more like this. The others, are the former.
Now the difference isn't so great, and the two different styles of getting there are a lot closer.
What if we used a less ideal center point? Here are two examples.
As you can see this makes a big difference, and is where most trip up. This is what you have to alter in order to get all three flare types to work the same in HR. - Now if you are building a horn around a PAR building style, and are siming the FR to taste, then of course PAR is the best choice.
Let's add one more section.
As you can see, both are pretty good approximations by this point.
All you have to do is understand where/what you are compromising, and then choose from there.