I haven't had a chance to post my impressions on the F18 I ordered. When my roommate first saw it after installing the sub into my HT, he seemed worried and thought I was going to blow out the neighborhood! It's definitely a sub that looks like it could bring down the house. Having said that, once I integrated the sub into my system with MiniDSP and the UMIK, I was surprised by how quiet the sub is. When I say quiet, I don't mean that the sub isn't as loud as it should be, but rather how well it performs its role within the system without drawing unnecessary attention to itself.
My Philharmonitor BMR's already play pretty low (~25Hz), so the Rythmik isn't necessarily giving dramatically deeper extension than what I'm used to. Right now, if I switch between "Direct" and "Stereo" mode on my receiver, which switches between Full Range 2.0 and 2.1, it's difficult for me to tell if the subwoofer is even on unless I listen very closely. When I did some REW measurements of my system without the sub, I was surprised to see how flat my bass response is for my Phil BMR's. It was very flat from 25Hz all the way up to 300Hz, with a dip (likely caused by my room) at 80Hz. Even below 25Hz there's "audible" (or felt) output.
When I hooked up my sub, the first thing I had to do was get the volume output of the subwoofer relatively in line with my speakers. To achieve this, I had to set the output volume of the sub within MiniDSP all the way to -18dB. Using this and the EQ (following advice form everyone in this thread), I've created for myself a generous house curve. After re-measuring, I'm very impressed with how flat the response is along the curve I've aimed for. Most of my music listening isn't done at high volumes, but if I'm cranking the volume then I've found myself turning output volume of the sub as low as -28dB.
I watched Edge of Tomorrow on VUDU. Based on what I was reading, I was under the impression there would be so much bass I'd find myself changing my pants. I heard a lot of deep bass, but aside from maybe a helicopter passing by in the beginning, I don't particularly remember being blown away by the amount of bass. Perhaps, if I turned the volume back to normal on my sub just for the sake, I would imagine there would be an uber amount of bass, but then it would excessively louder than my speakers. I suppose the point is that I thought, even in a system with a balanced response, the bass was going to be dangerously loud. I thought I would need the limiter and Rumble Filter on, considering the Rythmik guide specifically mentioned using these for this movie, but I'm having difficulty figuring out why I would need it. Are these protections exclusively for people running serious theater-sized rooms? If I'm running my sub at -18dB, does that mean I'm not really making the sub sweat much? Frankly I'm tempted to not worry about it that much because it's very rare there's a bass-heavy Blu-Ray that I want to see.
I'm sure I'll be spending a lot more time working on my EQ curve and moving around my 6 GIK 244 bass traps before I get the best sound out of the sub. At this moment I'm very satisfied. The low-end hits with much more ease and authority than it did through my BMR's. It also sounds like BMR's sound tightened up all-around now that they aren't on bass duty anymore, which is nice because I'm running them with a lot less powerful of an amp than what Dennis Murphy recommends. I've been using the cheapest Denon Bluetooth receiver from Accessories4Less for a few years now, so there's a lot more power now going into my system with this 900w sub
I'm sure in the near future I'll come back with pictures of my measurements and ask for specific advice or recommendations, but for now I'm very satisfied.