Every installation is different so there are really no right or wrong answers to this question, but here is some recommended guidance on ceiling speaker placement. Don't position ceiling speakers too close to a wall if possible. Doing so will create a 'boundary effect' which compromises the speaker's frequency response. Position your speakers in the best locations to provide good coverage of the space, and far enough apart to create a good stereo soundstage. For example, if your room is 4m x 4m then positioning your speakers 2m apart in the middle of the room would be about right. When installing 4 or more speakers in an open plan area, try and position them as best as you can for even coverage, but also consider that you might want a stereo pair in each area so you can enjoy a stereo soundstage while in the kitchen or sitting on the sofa. If using ceiling speakers for TV audio as well as music, consider placing them at an equal distance left and right of the TV for best stereo imaging. Don't worry if you can't position your speakers exactly where you would like. Lighting, air vents, skylights, timbers and steels are often obstacles which impact positioning. Fortunately, ceiling speakers have a wide dispersion and will still sound good if not positioned in the ideal location. Many in-ceiling speakers also feature pivoting tweeters which allow you to direct the sound back towards the listening area in this case. Aesthetics may also be important, so consider installing speakers in-line with downlights for example. But bear in mind that these may not be installed in the middle of timbers as the speaker would need to be, so factoring the speakers into your electrical layout is recommended.