Here's a couple of pictures with a bunch of screen caps that show a few interesting things. They also show how I prefer to compare different alignments. I'm not implying you did it wrong, simply that I do it differently. I prefer to compare max spl with the same low knee. Usually I do it with the same low knee with high pass filters in place but in the instance I did the same low knee without the hpf in place to make a point with row 3 and 5 in picture 1. There are a few points I want to get across and I wanted to do it without 200 screen caps. None of these designs are ideal but I didn't want to spend more than 15 minutes on this.
- Hornresp inputs for a ported box and a front loaded horn, both with same driver
- Schematic showing these designs are the same size (the ported box needed a massive vent to keep velocity down and it's still at 18 m/s at xmax which is a bit high)
- Acoustical power of each design at xmax
- Diaphragm excursion, just shown to show I am playing fair
- Acoustical power of both designs overlaid to show that when the designs are the same size there isn't much difference in output at the low knee - this is true of most resonant vented designs including tapped horns
- Acoustical power with hpf in place
- Diaphragm excursion with hpf in place
This shows pretty clearly that there isn't much difference in output at the low knee when the ported box and front loaded horn are the same size and have the SAME low knee. Once the hpf is in place the ported box wins by a bit. This also shows that low tuned ported boxes often have problems with port size and resonances inside the passband due to velocity issues.
Horns need to get exponentially larger as tuning decreases if you want flat response and ideal loading. A 30 cubic foot box with a 16 hz low knee as shown in the first post is extremely undersized, but as shown, even with this extreme limit some amount of gain is possible. Approximately the same amount of gain as a tapped horn of the same size with the same low knee.
Now let's look at the other extreme, the same ported box compared to a much larger front loaded horn. The horn still isn't large enough to be ideal size for the tuning but Hornresp has a mouth size limit so I did what I could. At over 14000 liters this isn't a practical living room design but it does show that massive gain and flat response are possible with massive enclosure size. While this design isn't practical it does become more practical if something like this is broken down into multiple units with multiple drivers and used in a large space. Multiples do work and if enough are used they will add up to an ideal full size horn, assuming the original design was an ideal full size horn with multiple drivers.