Subwoofers with room correction built in?

I’ll echo the last two posts and add that even the cheap 8033 from Dspeaker, which is only meant for subwoofers, works well, particularly if you dial in the woofers as much as possible (placement, crossover, gain, phase, etc.). I run such a unit from an additional line out on my line stage to feed the Dspeaker, which controls a pair of Rhythmik 15 inch subs. Those subs are not crazy money and really blend well with my hybrid horn set up. Note that the 8033 sums the bass for two outputs so no stereo subs (unless you have two 8033s or buy the fancier Dspeaker unit mentioned above). I don’t really care about that because I’m mainly playing LPs most of which are summed bass anyway and I'm rolling off the subs at 55hz on a 24db/octave slope. Pretty cost effective way to get synergy with a horn/hybrid that does not sound like two systems playing at the same time. It is seamless.

@redwoodaudio said: "This is an interesting option from Underwood hifi by DSpeaker: 8033 SII subwoofer equalizer. Just for the subwoofer."
That’s the unit I mentioned upthread. It is inexpensive, comes with a calibration mic, allows you to do repeated cycles with different mic placement and enables you to DSP just the subwoofers. That’s what I use with the 15 inch Rythmiks. I run it through another line out on my line stage. The main speaker system is not getting any signal from it and remains entirely unprocessed.
Very effective, both in terms of performance and cost, especially since I’m running those subs very low-- as mentioned, roll them off at 55hz on a 24 db/octave slope. The trick is dialing in the main speakers and woofers once the DSP does its thing- manually adjusting gain (including through use of a good SPL meter), phase, roll-off of the main speakers, their crossover point, etc. Still takes time and effort, and no remote, but it works well for me.