Assuming your drawing is accurate, your mix position seems to be OK on symmetry. What's important for your ears and brain is that there is symmetry in the front part of the room, ahead of your ears. Behind your ears doesn't matter so much, since sound has to take a longer path around that area before it gets back to your ears, and if your room is treated right the level of that "bouncing around" sound will be at least 10 dB down, and hopefully 15, by the time it gets back to your ears. And hopefully there will be a delay of at least 15 ms to make that trip, hopefully more like 30. If that's the case, then the rear of the room doesn't matter so much in terms of symmetry, since the sound coming back from there is quiet enough and took long enough that your brain can handle it. It's the part of the room between your ears and the speakers that is critical, but on your diagram you seem to be OK there. That's part of the reason for facing the speakers down the long dimension of the room: More distance=more time delay for reflections, and more space for treatment. If you turn your room sideways, in effect you bring the rear wall closer to your head, shorten the distance/time for bouncing waves, and have less space for treatment behind you. So even though symmetry might be better, you might be creating other problems that are even worse.
However, if you are concerned about symmetry and the "jog" where the couch is, there are a couple of options: 1) Drastic solution: Build a wall to seal off the window area, so that you get full symmetry. 2) Realistic solution: Build a couple of hard-backed gobo's-on-wheels that you can roll in front of that couch when you need to do critical listening, to simulate a wall to a certain extent, and roll out the way when you need to use the couch.
Here's a question: Do you get a clear, precise phantom center from your current setup? In other words, when seated at your mix position, listening to well recorded commercial CDs, if you close your eyes and listen carefully, does it sound like you have a third "phantom" speaker right in the middle, between the two "real" speakers? Can you clearly here center-panned sources coming from that phantom speaker
only, (such as vocals, snare, etc.), rather than from the left and right speakers together? Can you clearly point to the position of each instrument on the "stage" in front of you? If not, then you have an imaging problem. If so, then there's no reason to move your room around. If you get a good, clear, precise sound stage with a phantom center, then you are fine, from the symmetry point of view.
But even if that is fine., you might still have other issues with your room. Have you run an acoustic analysis of that room, to see what problems you do have? You said:
I currently have the room treated well with floor-to-ceiling bass traps in 4 corners and 703 on the walls (and ceiling directly above listening position),
I'm wondering if you might be killing the highs too much like that? Maybe you can post some photos of your treatment and your room in general, to get a better idea of what you have. I'm also wondering about your speaker setup, both in terms of the physical mounting method, and also in terms of geometry. There may be an issue with the way you have them set up. Once again, photos would help to figure that out. Also, what speakers are you using (make/model)?
If you haven't already done so, download REW and run the tests. Post the results here, along with some photos of the room, the treatment, and your speaker / desk / chair setup.
- Stuart -