Originally Posted by TheZaha
Don't plan on having Atmos (upgrading receiver) any time soon, so for the time being exploring upgrading from 5.1 to 7.1 as i move to a new room (currently using the S in dipole). I know the imagine S can be set to dual monopole - just not sure where best placement is once it's wired? Alternatively, thinking of using the imagine S as bipole and getting imagine mini for sides (or vice versa?)
I read back a bit, and I see your new room will be 15x25 (is that 25' length?). I've had a rooms somewhat similar to yours in the past: a 23x17 multipurpose room a few years ago where I wound up having to have the sofa about 3' from the back wall. And due to room layout (windows on one side, and too short a wall on the other), I couldn't do both sides and rears, so I picked up the Imagine S and tried it in dipole and dual mono modes. I ultimately used the S in dual mono to get 7.1, and it "worked" in giving me separate imaging, but the sides and rear sounds were sometimes smeared due to being physically too close to one another. When I measured them with my old Sherwood R-972 Trinnov Optimizer, the sides and rears were electronically at about 120 and 130 degrees respectively, which is too close for meaningful separation. Unless you have no choice, I'd stay away from dual mono if I could.
Personally if your room physically supports it, I'd do the Imagine S as the side surrounds in dipole (both driver faces firing, one towards the front and the other towards the back of the room, but the jumper connecting both sets of binding posts) ahead of bipole (the same, but the jumper disconnected so that you'd be powering each driver face independently). I don't think bi-amping these passive speakers will gain you much. But dipole might help make the front/side and side/rear transitions more seamless in a 5.1/7.1 world.
And in a room this big, I'd get the Imagine XB over the Mini if you're watching budget, since the Mini has a smaller (4") woofer/midrange and the power handling will be considerably less than your other floor speakers. I think the Mini is more expensive than the XBs, but you're also paying for the cabinet.
The XB have the same size woofer (5 1/4) and an identical 1" tweeter to the Imagine B, which is/was a bigger sibling to the Mini. But since you're using the speaker as a rear or side, the more robust construction isn't going to matter as much as when they'd be upfront mains in a small room.