Bass/Sub Bass Cab

yeah they do but they prolly can be cured, have you considered hd15 x1 and x12? [or similar ish arrangement] 

you could definetly design something that wil get you down to at least 30 hz with a v-18 in say a block of four [m~horn should do it] maybey some module horns [speakerstore] and some hd15s and mid top.

or even just four module horns and a pair of x-tros should do what you want.

30hz is not unrealistic! , lab, x1, almost most of the band pass subs on this site will do 30 if not 32hz] er, module horn will do 35hz with just two cabs, so with four youd see 30hz at a guess,

i recon minaximal had the best idea, design a horn thatl do 30hz with something like the v-18 or pd1850, or use a m~horn/lab horn

and do a kick cab to play 80ish hz up [will depend on what youv got on exact freq] and some sensible mid and top.

if you know what your doing maybey? [i dont so i cant say for defo, but if done scientificaly enough and endowed with a decent driver and an apropriate back cahmber something like that may be done, dont quote me on that]

maybey you could extend the 1850 / 186 horn [or basicaly design some thing new but this would be a possible starting point] and whack a serius horn length.

minaximal knows a fair bit about 18" getting down to 30 hz and a bit lower, afaik his terra horn does this, and he proly wont give you the design , but hel prolly tell you how to go about designing your own [hes already posted a few pointers] go on design your own, something like a 186 thatl get down around the 30hz maybey 28/29 hz in a group of 4/8 might not have the output of a lab [might do though] but it should defo be doable, maybey if a few peeps threw you some pointers you could get yourself a rather nice, 30<100hz sub horn, like a true lab rival.   if you got the ability to design, you can prety much garaunty some one on here will help if you get a little stuck, i can imagine a few peeople would like to see them too! [i would] go on go for it! you know you want to!

sometimes bandpass horn hybridscan produce better results indoors.....

i dont know...