\rHi Mike,
Based on your photo, I believe a patio speaker would be a better option. In fact, I would suggest two of our AP550TT Dual Voice Coil stereo speakers connected through our OVC300 outdoor volume control. Because this is a stereo speaker with two tweeters, it provides more music coverage (to your large area) with no concern for right and left separation. You can easily mount them 12 to 15 feet apart with the included bracket. The volume control matches the two speakers to your receiver and allows you to control the volume while in the patio. You can connect these to either the A or B speaker output from your receiver. You will need to use our 16 gauge 4-conductor CL3 rated cable. A patio speaker features a tuned enclosure specific to the drivers utilized. The in-ceiling speaker is subject to the area it is mounted in and the enclosure behind it, which (based on the image you sent) could vary greatly.
TL\r