Experience with Emotiva Ultra Sub 12
This is my first post here, and I am not a sophistacted user, so take this for what it is worth. This is a great site, by the way, with lots of knowledgeable people. I appreciate all the time and effort that it takes to keep such an endeavor going.
As part of some work that has been going on in my home, I decided to upgrade my aging home theater setup. The living room is approximately 4500 ft^3, and roughly rectangular in shape. There is a fireplace in the center of one long wall, with the a/v components to the left of it. The right front speaker is to the right of it, so it is a bit unbalanced in layout. Current speakers are all Mirage- M-790's for front, M-490's for surround, center is OM-C3-1, and sub is PS-12-90. Most components are early to mid-90's vintage.
As part of the changes I swapped an old NDA T-761 AV receiver for a Denon 2310, and ordered an Emotiva Ultra 12 sub and their surrounds.
I hooked everything up, using the new sub in the right front corner. Before running the audessey, the sound was good, but not great. After running the Audessey, the sound was amazing! The trebles and mids had new life to them, great depth, and I felt totally immersed in something incredible that I had never heard before.
The bass was musically perfect. With the old setup I could sort of feel the lower bass, but there was no definition to it. I could hear low tones, but there was no shape to them, and I couldn't distinguish what note was being played - it was just generally 'low'. That had pretty much been it for years now, and I had decided that my hearing had deteriorated enough that I wouldn't be able to distinguish low notes. Even more, I had decided that that all the clamor about subs was pretty much marketing hype.
All of a sudden, I"m hearing bass with precision and clarity. The sub, however, had just disappeared. Did I mention that I was rather unsophisticated at this?

) Another thing I didn't mention was that I have bi-amped the front speakers, which really did breathe new life into them.
On movies, though, I was a bit disappointed. I didn't feel the visceral impact of the bass in my chest, which I was hoping for from a new sub.
So, I congratulated myself on having the foresight some years ago to buy such great speakers and the new receiver, and decided the sub wasn't really adding anything, and packed it up and shipped it back to Emotiva.
Big mistake.
That evening, I hauled out the old sub and hooked it up, thinking that it would provide a bit of impact for movies and little else. The bass was back to the old muddy sound, and the mid-bass had lost some of the depth. The highs still sounded good, but the overall experience was many notches below what it had been. It is still a good sounding system, but without the tight sub it is not at all exceptional. My wife, who is not all that excited about the whole thing, also commented and asked me what was wrong with the sound now.
So - conclusions. The Emotiva sub has an amazing sound, but is not quite powerful enough for the size of this room. I'm continuing my online sub shopping, now looking primarily at 15" subs with a bit more power to give me that desired impact. The ones that I'm considering include:
Hsu ULS-15
ED A7S-450
Rhythmik 15" subs
Epik Empire.
All of those are out of my price range, but I will stretch if I think there will be a significant impact.