They already do, the 1802...
No, the 1802 only digs down to barely acceptable Hz levels. 26Hz @ +/- 3dB isn't remotely competitive with other horn or tapped horns, let alone the DD-18s. For music, sure. Great. However, for HT, it's a non starter.
Sorry, but, complementing their CINEMA LINE, is what I was addressing.
It's not truly deep. It's just a common sub. Not even a deep sub.
Just because THX doesn't specify down to the sub 10Hz levels doesn't mean it's not there in a soundtrack. So, talking about THX spec is meaningless and pointless when it comes to HT, which even you further allude to. So, I'm really not sure who you're arguing with. Me, or yourself.
The specs are comparable specs (similar environment). So,Unless it's sub 10Hz they are non starters for me. Praise them all you like. I can hit lower, louder and harder with smaller. I'd like horn but the 1802s just aren't in the running.
I support the horn loaded argument. I'm simply saying it's not practical for HT with current offerings when you want a fair and reasonable space allocation for the sub(s).