Hi Ralph:
I would go with Patio Speakers like our AP525 and mount to your beams. The advantage of the sealed patio speaker is you can aim it for better coverage than any in-ceiling speaker. The AP525 has a two way mounting bracket that does the typical swivel and with the unique adjustable mount you can tilt the speaker as well. You can still run your wires in the ceiling and cutting a small hole above the speaker to connect. You will wan to mount the speakers 6 to 8 feet apart. The AP525 and AP650 (the 6.5 inch version ) have the highest outdoor rating. And unlike a in-ceiling speaker the Patio speaker has the tuned cabinet that sounds the same no matter where you place it.
If you have good access behind the ceiling you could possibly use new construction brackets but the in-ceiling speaker will not match the mounting flexibility or sound quality of the patio speaker available in white or black finish.
TL/4528