There's some serious bass capacity at hand here from several individuals, be they an incarnation of direct radiators or horns. It's not that I'm complaining or in a lack of capacity in my own set-up, but ~10-15Hz extension and a radiation area in some cases multiples to my MW's is, well.. impressive. Maybe I'm a bit surprised,
, that you went from 8x18" to a pair of über-dittos "only," but I take it they're doing perfectly fine
Whilst still my main focus is horn subs I'm glad to see any bass principle present here. 10Hz extension from a horn would seem nigh on impossible in most domestic environments, but I'm surprised to learn the DTS-10 tapped horns go that low in-room while not being more physically imposing (not that they're small by any means) - with the proviso that upper end extension is fairly limited, I guess, and that "irregularities" here may affect midbass presentation even with a steep low-pass filter between 50-60Hz (?).
In that regard, unless one is able to house ginormous FLH's, I take it direct radiators are the most obvious solution to achieve ULF territory, without being the size of a house and maintaining a well-behaved and -extended upper end response. The latter in itself, I presume, could be instrumental in midbass cleanliness?
For that reason certainly I've chosen not to go with a tapped tuned too low - that is, not much lower than ~25Hz - and that's also saying that if one wants a more representative picture or a fuller potential of the sheer bass quality from a tapped horn, perhaps the DTS-10 isn't the ideal choice. I'd even wager that insofar the pursuit of ULF is as prevalent as it is (from a tapped horn, not least), midbass quality seems not to be priority numero uno. Perhaps that's why you abandoned the DTS-10's to begin with,
Feels like I'm repeating myself, but I do find horn bass to sound different compared to DR's. Period, end of story. No one has to agree with me (though some does), but I'm not hearing any ghosts here. For sure, I'm won't deviate from horn bass either, and I'll gladly give up 10Hz in the bottom range to have what's provided from >20Hz. Maybe I'd only have to miss out on ~5Hz with a pair of 21" B&C-loaded SubMaximus V3's, but hell, I cant think of how to house them.
It would seem the DR ULF-capable subs brethren find they can have their cake and eat it too (i.e.: ULF and A+ overall bass SQ). I can't say the same lacking infrasonics, so there you have it...