What you're hoping to do is something I've been evolving for 30 years starting with passive components and 10+ with digital XO starting with a Minidsp 4x10 to do XO, time, EQ and SPL corrections to the diverse drivers involved in a 3-way XO + subs. FYI, Minidsp hardware Sharc processors are pretty limited with what you can do in bass frequencies and the basic Dirac they offer is also pretty crappy by comparison. I do it all via computer now which allows far greater flexibility.
I built these HUGE monkey coffins based on the "golden mean" dimensions in all the speaker building books back in the 80's following all the T/S guidance available at the time and they are dimensionally huge sealed enclosures (I'm committed, 180 liter, 6.4 cubic foot) to adequately cover the frequency range of 30-20kHz I was hoping for. In retrospect, in futility. The enclosures have remained huge but have undergone massive internal changes over the years as well as speaker drivers as I learned better practices, gained access to better software tools and trying to understand half of what some of the really smart people here know.
I know you're looking at 80-120Hz zone but if you want to activate the room and reinforce the presence in that frequency range get some subs. I'm in a 16x20x11', 3500 cubic foot space and XO my 15" woofers to two subs at 65Hz because it works better in MY space and speaker placement.
My goal has been to have an even sound throughout the room (it's my art studio, I move around) instead of a specific listening position so have added some absorption and diffusion for my specific needs.
Some things not mentioned often enough when going active. Sorry if obvious but I learned the hard way.
- Pay specific attention to the sensitivity of your W/M/T combination with the intent in advance that you're applying EQ and DSP which will automatically reduce your overall SPL.
- Also, very important, the input sensitivity and voltage gain for the amps you want to use for each driver speaker pair. No use really having a stellar SINAD for your tweeter amp if it only has 13dB of gain and now you have to pad down your 89dB sensitivity woofer to get to your 94 SPL/w/m tweeter audible.
- With larger midrange drivers (5" +) they start to beam at lower frequencies off axis. Be aware of this depending on the directivity you are hoping to achieve with your build.
- Impedance of driver selections in harmony with each other and the amplifiers that are driving them - voltage limited vs power limited.
Current configuration of drivers to fill in what's not in the sig:
GRS 15PT8 15" woofers
B&C 6md38 6.5" midrange
Audax two34xo 1.25" dome tweeters
15" Dayton rss390hf-4 sub + a SVS 12" SB1000 in opposite corners (not ideal but necessary)
currently using LR4 XO at 65, 350, 1500kHz but one of the subs uses a gentler slope on the HP because it integrates better somehow with MY room in SPL and phase.
Good luck! Have fun! I know you will, I have. It will, eventually, sound awesome!