Have you ever taken post Optimizer sweeps using REW to see how well your subs interact together once Trinnov calibration is done?
Not since I first set it up, when the measured results closely matched the "post" curves the SDP-75 (Trinnov) produced, and about that time a Windows update took out my HDMI driver and I've never fixed it (that was maybe three years ago; life got busy). A reminder to self that I really need to get that driver working again...
Definitely getting a lot of input on the AVS forum that if I'm using two or more subs I will only get a good result if I use REW and either a MiniDSP or the Active Crossover section of the Trinnov to either EQ all the subs together as one input or apply post correction PEQ+delay+trim.
Yup, that is the usual advice, but I was violating it before getting my SDP-75 and since. It takes some futzing around either way, and chances are I ended up manually doing what a miniDSP might do, but my response has always been decent. My plans were to take measurements and compare MSO to SFM and such but I just never had the time and/or strong enough interest. You can run something like MSO and manually enter the filter coefficients into the Trinnov -- that was my plan, since I have enough channels to put each sub on its own channel. Ditto with SFM (Harman's Sound Field Management). Trinnov has always claimed their way worked just fine as-is, though also claimed to be working on a more advanced scheme (I have lost track, again free time has been nil the past few years, or I've been too tired to tackle it).
I'd suggest setting it up and running it first, see how it does, then look into alternatives if need be. You can always do it later, and it is not all that hard to run once you have all the pieces in place (UMIK-1 and REW plus the connection to the Trinnov, then run MSO or whatever and enter the filter coefficients into the Trinnov, miniDSP, etc.) From what I have seen, bearing in mind I have not kept up, results are pretty widely varied and a function of the room, natch. Some have seen great improvement going the miniDSP route (or similar), whilst others have had good response straight from the optimizer. I am sort of in-between; I ran the Optimizer then tweaked sub and SDP-75 settings to dial everything in for the best bass response (focusing on the crossover region). I did the same with MCCAC and Dirac Live when I was using them. It took me a few afternoons spread over a month or two as I had the time, though I was able to get it pretty close the first day or two I set it up (I was able to set aside a weekend to play with it).
I am the perfect candidate for a miniDSP, Accourate, etc. -- if not for an insane work schedule and too many other things going on in life. I got mine good enough for now and will tweak when I have more time for it.
But do wade through the other thread that
@Olli referenced -- there are a lot of measurements there and a wealth of discussion. I have found what works to be very dependent upon room, speakers, and listener's goals so do not believe there is a single solution best for all. Multiple measurements and using MSO/SFM/etc. is probably best for frequency response and such, but the trade is the effort (HW, SW, and time) to achieve it. I have always planned to expend the effort, but what I have now is "good enough" that I have not felt the need in the face of other obligations. I did spend a couple of weekends tweaking it in to get what I consider good response, but have not done much since except rerun the Optimizer as things changed. I hope to retire soon (a moving target) and have more time to play.