dual 15 inch loaded sub

hi

recently have become fascinated with the concept of designing my own bass horn. it appeals to me because I yearn to do something other than just build a public domain 18inch Flh and stand out from the hoards of other rigs. Im slowly working my way through all parts of the dinsdale horn guide combined with loads of other reading material and while doing so, I became intrigued by the possibility of designing a dual loaded 15inch horn exponential horn. 2 15 inch drivers would yield more acoustical output and power than a single 21inch while also being cheaper so it seems strange that no one has done this. am I wrong? is this a concept worth perusing? really any input from more experienced horn designers would be helpful here.

I will do. I stumbled across the Lab 15 driver and I belive it is the perfect contender for this sub. This box is going to be huge, 1340 (to fit flush with ES218) by 1220 by 700.

You will still need 1.5m free space after the door to make a turn

And the door has to fully open