Thanks for all the good information guys. I'm recovering from surgery, so figuring out some of the specifics of future projects is a good way to keep my brain from eating itself. I've spent the last hour or so trying to figure out WinISD. I think entered the info correctly, but I don't yet know how to read the graphs in order to optimize anything.
The curious things about back loaded folded horns to my thinking is that it seems to indicate that air volume, venting, and materials seem to take a back seat to path in those designs. What does a certain path do? Very curious. I can see I'll probably be starting out with simple closed or vented designs like the uFonken and not trying a back loaded folded anything very soon.
The only reason the folded horns look like a maze is because they are folded, and the only reason why they are folded is to make a cabinet with reasonable dimensions. Unfold the horn and you would end up with a speaker cabinet that would be difficult to fit in a standard room!
cogitech, do you find WinISD to be less confusing then other software design programs? I'm not understanding much about the graphs and calculations yet, but that doesn't frustrate me too much. This is a new thing for me. Really, it more of a break from some of my other projects--a shop made 16" bandsaw and a Hall Taylor rocking chair.
I actually find WinISD to be fairly straightforward, but I didn't necessarily feel that way the first time I used it. There may be video tutorials on youtube, but I've never looked for any.
Basically, once you have your driver T/S parameters entered into the DB and start either a sealed or BR project, select the number of drivers, etc. then WinISD will automagically calculate a box for you. You can play with box volume and port tuning (only in BR, of course) and the graph will change accordingly. It is a simple frequency response graph which shows you the lower end of the frequency response graph (that is what the cabinet is affecting, after all).
By playing with the box vloume and port tuning, you can sometimes stretch the response out to something you think you would like better than what WinISD came up with. Try tuning it lower if you want more bass response, etc. There are always trade-offs. Ideally you have a flat response that tapers off in a nice smooth curve, for the "highest fidelity". Traditionally, one would try to avoid big dips or humps in the curve, as that will tend to result in unbalances low end frequency response. So, as you continue to tweak the volume and port tuning, you can come up with a compromise that you are comfortable with. Aggressively low tuning with some -3 to +3 dB humps or dips? Perfectly smooth curve, but with ultimately less low end? It's up to you.
Then you change the box dimensions to what you want, maintaining the volume you decided on while playing with the graph. Finally go to the port (vent) section and specify a suitable port diameter. The length will be calculated automatically for the tuning you chose earlier. Make sure the vent speed doesn't go too high or you will get vent noise ("chuffing"). If the vent speed is too high, increase port diameter (but be aware that the length will also increase quickly. Find a good balance.
The one thing to be aware of is that if you push the tuning really low on a driver that is not designed for it, you will reach the driver's maximum excursion (Xmax) very quickly. What this means is that you will need to be very careful with the volume control if you push a driver beyond its intended use.
Prime example is the nanoTowers. I have received plenty of criticism from the experts around here (and I am sure it is well deserved) about my design and how the little Tang Bands are not meant to do what I am doing with them. The thing is, I am typically pushing less than a watt through them and even when I do push them harder, they handle it without any perceivable issues. I got lucky with my design. I rolled the dice and it worked out. My next dice roll might not. That's half the fun.
