Are those speakers enclosed? If not, then much of the problem is that the ceiling is not yet finished. In-wall and in-ceiling speakers are designed to use the enclosed area behind them as the speaker's "box". Without the box, the speaker will sound weak, with poor mid/bass response.
In order to test these speakers properly, you need to give them an enclosure. Contact the manufacturer to get the correct dimensions for the box, whether to include any filling ... etc. Once the boxes are built, you can just install them, as built, knowing the response you got in testing will not vary much (if anything it will be improved) once the ceiling is completed. Fortunately, you have lots of room for the box/speaker, so you do not have to compromise on the enclosure.
If this all sounds like too much trouble, you can always just install them, as is, and hope for the best when done. If you go that route, install the smaller speaker on your first try. You can always cut a bigger hole for more speaker, if needed, but re-installing in a smaller hole is a PITA.
You might also play around with positioning, before you complete the ceiling. Which positions give you the best room coverage, especially in the positions you most use (stove, sink, prep area, breakfast bar)? Getting an evenly balanced stereo sound at each position may be more problematic than you envision. Much depends on the native frequency response dispersion characteristics of the speaker itself. If, in your testing, you find this to be an issue, you might consider sending a mono signal to each speaker. Yes, you would lose the stereo effect, but that is the better trade off to losing an entire channel or half the frequency response of one channel when standing off-center. Then, the speaker placement becomes one of room coverage vs positioning for stereo effect, and could even result in more than two speakers being used.
One other approach is to cater to specific areas with stereo speakers. So, you may have as many as 4 sets of speakers, each positioned to give good sound to a particular area.
Fun project. That ceiling will look quite nice, when done.
In order to test these speakers properly, you need to give them an enclosure. Contact the manufacturer to get the correct dimensions for the box, whether to include any filling ... etc. Once the boxes are built, you can just install them, as built, knowing the response you got in testing will not vary much (if anything it will be improved) once the ceiling is completed. Fortunately, you have lots of room for the box/speaker, so you do not have to compromise on the enclosure.
If this all sounds like too much trouble, you can always just install them, as is, and hope for the best when done. If you go that route, install the smaller speaker on your first try. You can always cut a bigger hole for more speaker, if needed, but re-installing in a smaller hole is a PITA.
You might also play around with positioning, before you complete the ceiling. Which positions give you the best room coverage, especially in the positions you most use (stove, sink, prep area, breakfast bar)? Getting an evenly balanced stereo sound at each position may be more problematic than you envision. Much depends on the native frequency response dispersion characteristics of the speaker itself. If, in your testing, you find this to be an issue, you might consider sending a mono signal to each speaker. Yes, you would lose the stereo effect, but that is the better trade off to losing an entire channel or half the frequency response of one channel when standing off-center. Then, the speaker placement becomes one of room coverage vs positioning for stereo effect, and could even result in more than two speakers being used.
One other approach is to cater to specific areas with stereo speakers. So, you may have as many as 4 sets of speakers, each positioned to give good sound to a particular area.
Fun project. That ceiling will look quite nice, when done.
