I have qs8's and qs4's . Originally started with the 4's then moved them to my bedroom and bought the 8's for my theater room.
I originally had them down low but was advised to move them up to about 2/3's and a bit forward of LP. When I moved the 4's to the bedroom I put the about 6" from the ceiling and that turned out to be a really good spot for them. I have the 8's also about 6" down and it works great. I was able to localize the sounds from them before but now they blend in well with the rest of my system. If you can try them in various spots to find what works best for you. The height of your couch,whether you recline and your ceiling height play an important role. If you have low ceilings or are close to the back wall you may want to ceiling mount and tilt them down though I don't think this type of speaker really requires it. You will have to hit studs if you ceiling mount them which may limit where you can put them.

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