I'm glad that I could be of great help here!
Playing around with Edge, you'll find that you get more baffle gain if the source is located more towards the middle than the edges of the baffle (or more towards the middle and then the floor for a sub, because of the "mirrored sub below the floor" in a half space scenario).
I've been fiddling around with hornresp to come up with a cab that is smaller than the 21ipal loaded Skhorn (which is rather huge unless you're a rental company with big trucks and a range of smaller subs than the Skhorn for the times where it's size and power will be too much), that has more frontal area relative to the depth of the cab and the source located at the bottom of the cab (to be able to get more baffle gain both in singles and in multiples), that extends as deep as the Skhorn(for comparisons and good extensions sake), that is easier to build, is cheaper to build(the 21IPAL sure is pricey), that is preferably as powerful(because power), and that rolls off above 100-120hz(to roll off distortion).
I've kept the 6th order concept. It really is a power dense and good sounding design if done right. I've split the cab in half, ie, one 21" per cab, and therefore and for the prices sake I've gone with the 21sw152-4 instead. That is one great driver in price/performance, performance/weight ratios, in (Bl2/Re)/(Le/Re), and it's also 4ohm so they can be run in singles, and wired in parallel with two per amp channel if needed. For comparisons sake I've kept the volume per driver identical.
I've straightened out the 'horn' part of the Skhorn, because I often find in my simulations that keeping ducts straight is more space efficient than flaring them. They're also easier to build.
So, what I've come up with is a regular bandpass cab with a great driver lol. Pretty simple really, but with complex reasoning behind, as usual with us nerds.
Hornresp inputs: (I simply selected quarter space instead of selecting 2 speakers all the time in the tools menu.)
The form factor of the cab I have in mind would be 24" deep, 25,5" wide and about 34" tall. Slot port at the bottom, driver vertically mounted pointing forward in the cab, the hf sections slot port would be just above the lf sections slot port. Two cabs next to each other simulated in Edge would look like this, my cabs in red and a Skhorn, laying vertically, simulated in blue:
Despite having the exact same total volume, my cabs have just shy of 1db more baffle gain down by 40hz, rising to just shy of 2db by 100hz.
In the sims I've tried to subtract the baffle gain from the hornresp response both with the cab design and the filters used. If you add the baffle gain back you'll get a flat response with a high pass at ~100hz. And oh yeah, unless I want to see the raw response to look for warning signs, I always simulate with the filters in effect and try to go for a flat response(if the baffle gain would have been added back) with only the filters in use. The cabs will always be used with filters anyways so it makes most sense to sim it like that, I think.
21ipal Skhorn in black, 2 of my cabs with the 21sw152-4 in grey. Both have 12db/oct hpf and 24db/oct lpf, set at different points to adapt to the different responses, excursion behaviors, and so on.
So, yeah, about the same difference as in the Edge simulation, but inverted. The two responses should match up very well with the baffle gain added.
All in check so far. By all accounts, everything so far is pretty much the same. Response, phase, delay and efficiency is pretty much exactly the same. The excursion differs, but they are both in check. What differs is the power per driver:
The Skhorn seems to need about 40% more power to get the same job done. Now, in my book, that's a huge difference. Especially considering that the drivers in the Skhorn are about 75% more expensive and the Skhorn has to be brought in in one piece whereas half of my option can be left at home if one would want to. My design has no angled pieces, so it's a bit easier to build. It rolls off fast above 120hz to roll off distortion, as shown below:
Now, could the 21ipal be used the same way and reap the same benefits as my cab loaded with the 21sw152? IMO, not practically so. One driver per cab loads the amp with too low of an impedance, so a pair is pretty much the only viable option. Would you like a double loaded cab that is 24" deep, 36" tall and 48" wide? I don't know. I wouldn't. I like to have a bit of scalability.
Areas where my design can't beat the Skhorn is the force cancelling mounting and how deep inside the cab the drivers are buried. I think less power needed, cheaper amps, more scalability, cheaper builds and easier builds outweighs the cons by a pretty good margin though.
Now, I don't mean to take a crap on Ricci's work. The importance of the work he/you have done can't be overstated. I just wish to contribute with my .02$ and to shed some light over this whole directivity deal, and show an example of how one can use it to one's advantage.