Greg used it in a 4.2 cubic foot volume tuned to 32 Hz and yes, WinISD does yield smaller volumes with less bandwidth.
I do have a pair of enclosures in progress that are something like 3 cubic feet tuned a bit higher for more impact. The AutoCAD drawing is on my laptop which I don't have access to at the moment. All the MDF is already in the garage stacked next to the table saw and, true to form, it's been there for months.
My plan was to build "B4" volumes with the option to tune them as "B6" volumes for response to 25 Hz. I figured that was as low as I wanted them to go.
I'm not sure what volume/tuning 1audiohack evaluated a pair in. I'm not sure what volume/tuning RobH3606 plans on evaluating the same pair in. I'm not sure what volume/tuning hlaari plans on using. Jerry Moro wanted to know how we all used them and whether or not we liked them. He mentioned that he didn't have a whole lot of experience with system design so he was interested in our feedback.
The 1500AL in the 4.6 cubic foot volume tuned to 28 Hz is a real work of art. The 1501FE won't beat it, but it should be very nice in its own right. Plus it isn't as heavy or expensive, albeit just as impossible to obtain. Rather irritating actually. To this day neither Greg nor Jerry seem to be able to fathom why it is impossible to get these transducers or their recone kits. I've read some of their internal emails and they seem totally perplexed. I suspect Harman simply doesn't want to stock anything and that means not building spares.