I'm currently using PSB Image B15 bookshelf speakers on stands for the L/R/C channels and rear surround with Image S50 Bipoles on the surround sides just behind and to the side of the couch. This is used in combination with a Definitive Technology Powerfield 1500 (15" 250 watt) subwoofer (brought over from the previous system I had that used Carver ribbon mains with Def Tech Bipole surrounds; the Carvers have since been used in a 2-channel fully analog system in my newer house complete with turntable, custom active crossovers, etc., although I recently added Klipsch surrounds to get 4.0 (with an old outboard Technics DD/DTS decoder so as to not have to ditch my separates fully analog Carver C5 Sonic Holography pre-amp) and the Klipsch speakers bounced off the side walls (mounted low on the floor by the main chair) match much better tonally to the Carver ribbons than the Def Techs did. That room has a 48" plasma mounted on the wall above my piano which sits between the speakers (combination music listening room and recording studio and now can watch TV/Movies as well).
Anyway back to the primary theater room, the Def Tech sub crosses at 80Hz. This is used with an Epson 3100 1080p/3D projector (formerly with a Panasonic PT-AX100U 720p projector) and a 93" screen with the main seating location about 10 feet from the screen (projector around 12-13 feet away mounted on the drop box center beam (2 feet below main 8' ceiling). There's about 12 more feet to the back of the room with a B15 Surround (the center speaker matched 'pair') in the rear center position (6.1 speaker configuration). I've attached a rough diagram thrown together with Photoshop and an older photo of the room (Panasonic projector in place).
I'm currently looking at upgrading my old Yamaha receiver to a newer one and I'm considering possibilities for Dolby Atmos and DTS:X. The old "Image" line is gone ("Imagine" seems to be the current thing) and I'm wondering just how tonally compatible some of those speakers are. The Imagine XB seems to have very similar specs to the B15 (similar size, bottom end and crossover points). The Imagine B seems somewhat similar to the old Image B25, although it doesn't go quite as deep and certainly the Imagine S Surround looks quite similar to the S50 surround but with the tripole wiring/switch capability to do dipole and separate monopole "7.1" modes.
One non-Atmos related issue I've had with this setup is that the optimum subwoofer setting to blend for 2-channel music is about 4dB higher than the setting needed for most "x.1" LFE soundtracks (at least to my ears and the room walls shaking versus music sounding proper). Unfortunately, the Yamaha receiver makes no distinction between the volume setting for the subwoofer for fill-in bass with satellite speakers and the LFE channel. I'm wondering if other newer receivers have separate settings for this adjustment. I was even considering a PSB tower speaker (e.g. X2T or X1T) to give me better stereo bass so the sub setting would largely just be for the LFE channel. Ebay seems to have several available slightly used for reasonable prices. But how well would this match with the B15 still used for a center channel? Would I need a pair of Imagine XB speakers to get an exact tonal match? I expect the room shaping and parametric equalizers most receivers have (even my current Yamaha has parametric with a mic to even out response between speakers) could probably get them reasonably close even if there are some differences. Certainly, just having the S50s on the side walls changes their character to some degree despite matching drivers.
That brings up the question of the S50 surrounds. They're bipole, not dipole which at the time of the transition from Dolby Pro Logic to Dolby Digital in the 1990s, they seemed the best compromise between Pro Logic's high mounted dipole non-directional surrounds and the more direct pin-point imaged Dolby 5.1 type sound. Probably close to half my movies are either Mono, Stereo or Pro Logic (I have a large 1930s-1950s movie collection including 70...yes 70 Humphrey Bogart films; all that I could locate as I'm a big fan) plus quite a few movies from the 1960s to the present as well (around 700 movies total) so I'm not totally keen on ditching the S50s bipoles which do a good job with older Dolby Surround soundtracks and yet still image surprisingly well with 5.1 and 6.1 soundtracks (I'm not really buying some of the comments in this thread about the PSB side surrounds being worthless with Atmos as they are quite good at imaging stereo surround just the same (I've got a lot of DTS and SACD surround type music albums as well and I think I'd notice if they were as bad at pin-point imaging as some people imply. What probably doesn't work so well is the Dipole mode on the Imagine S speaker that looks like the S50. That would be nebulous sounding, but bipoles aren't nebulous when fed stereo signals, only somewhat so with mono signals (hence the nice compromise for Pro Logic and Dolby Digital type soundtracks). I'm not saying they're optimal, but trying to get a perfect system for Dolby Surround, 5.1, 6.1 (EX/ES), 7.1, Atmos, DTS:X and Aurosound 3D all in one room might be a bit challenging. Some layouts are close to each other, but I don't think any speaker setup is "perfectly ideal" for every one of those. Whether one would even notice without direct comparisons is another matter.
The rear sliding glass door and half bath limit my ability to put a direct firing speaker on the left rear side of the room without blocking the doorway. This is why I went with a rear center (6.1) configuration (plus you can only buy B15 in pairs so I would have needed yet another pair to have 3 for L/C/R plus 2 for rear surround). I'm also not keen on mounting speakers on the ceiling so I'd be looking at a bounce "Atmos Enabled" type speaker for height.
The configurations I've considered given the layout relative to the existing setup shown in the diagram and described above are:
1> Remove rear surround and put a pair of Xb speakers behind my couch pointed to either side wall to get stereo rear side surrounds in combination with side S50 along couch. Add Xa Atmos enabled speakers on top of left/right front speakers and put a pair in the back of the room (can't get them too far apart due to the back door) so it reflects off the ceiling back to the couch from front/back accordingly.
2> Change PSB S50 side surrounds to Imagine S surrounds and use the 7.1 mode to get side/back surrounds that don't block the back doorway. I'm not convinced this would sound very good, though since there's very little separation between the front/back ends of the speaker. I have the feeling that Xbs mounted below ear height behind the couch pointed to side walls would reflect back and simulate rear side mounted surrounds where I can't put them (option #1)
, but this would certainly be cleaner looking (less speakers all over room). I can't really play with the position too much, though becuase I already have wall mounts installed and there's a drop down "box" in the middle of the room (center beam of house and what not) that limits position (makes for a slick place to mount the projector, though as you can run white wire molds along the back and not show wires without trying to get it through the ceiling).
3> Use a 9.2 receiver and have the Xa height speakers in the front only and maintain current "6.1" rear surround in the back of the room for non-Atmos 6.1 ES/EX and 7.1 soundtracks while Atmos would have a 6.1.2 configuration.
4> Get a 7.2 receiver and configure Xa in the front for a 5.1.2 configuration and give up rear center (I only have a half dozen or so DTS-ES soundtracks anyway plus another 12-16 "7.1" DTS-HD MA soundtracks and a mere 6-12 (?) TrueHD + Atmos "7.1" soundtracks at present. Frankly, if they keep EXCLUDING Atmos from regular BDs (as some studios are starting to do like Sony's Ghostbusters 2016 that ONLY has Atmos on the 4K disc but not the 3D BD or 2D BD, I don't know how much Atmos I'd be seeing in the future. My Epson 3100 is 1080p/3D, not 4K and I'm not crazy about spending $30 for Ultra4K discs that are just going to be down-converted to 1080p when the 1080p versions are often $10-15 or less these days JUST to get an Atmos soundtrack that SHOULD have been on the 1080p BD as well (seems to be done purely to "encourage" people to buy Ultra HD players; well I just bought a PS4 not an XBox 360 so I'd need another UHD player to even use the discs. The only one I have is Ghostbusters because the 3D BD only came with the 4K set (and it was on sale for $15). Does Sony think I don't want to hear Atmos on the 3D version (and it's pretty darn nice in 3D so it would be hard to choose between 3D and 4K even if I did have a 4K projector and a large enough screen to actually see 4K resolution...but now we have HDR/WCG to blur the lines even more as they are 4K "features" but have nothing to do with the extra resolution itself.... (sigh).
Dolby's site promises Atmos support on Vudu, but I'm somehow guessing they will magically only appear on their 4K titles (despite the fact it's just Meta data and even DD+ can carry it). The industry will do anything to force 4K type sales, it seems.
Anyway, I'm curious for any comments on how the PSB Imagine S Surround sounded in 7.1 mode (saw one comment already and it wasn't so good) and how the Imagine line sounds compared to the Image line, etc. I don't want a tonal disruption nightmare on my hands.