Mario, never mind trying a diagram; describe where the left QS is in relation to you. Just saying rear wall doesn't narrow it down enough. If it's on that wall, but still about as far to your left as the other QS is to your right, then if the left surround is just a couple feet farther back that wouldn't be a very significant problem with the very wide dispersion QSs.

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Enjoy the music, not the equipment.