Technically speaking, since the speaker's weight is around 65 pounds, you could use a product like the Snaptoggler
in your double drywall ceiling, using a minimum of four per speaker bracket. However, I'm not big on using drywall anchors for heavy (and expensive) things suspended above my head in a vibration-intensive area.
The only alternative is to open a 'window' in your ceiling to mount securely to the structure...and do so in a resilient way. I've made you the attached sketch, which is definitely not to scale!
I propose making a mounting block made from two layers of 3/4" plywood with Green Glue in between. 1/2" Neoprene can be attached to the entire underside of the plywood. The base of the speaker mount can be attached to the neoprene side of the plywood using through-bolts and a locking washer with two Nylon threaded nuts. Next, I would attach a full perimeter of 2x2 blocking (side blocking for attachment, cross blocking for a bit of additional support), leaving the blocking 1/4" proud of the plywood on all sides and fitting the width of the joist bay precisely. Attach the blocking to the plywood by screwing down from the top. Now you have a full mount that you can position up/down and forward/backward within the joist bay to get the speaker height and position you need. Secure the blocking into the side of the joists with 3" wood screws.
I would then attach putty pad to the part of the post that will penetrate through your double drywall layer and then create a 'clam shell' of two layers of two drywall pieces with a slightly oversized square just larger than the penetrating post while still getting a bit of compression from the drywall into the putty pad. Trim away any of the protruding putty pad and make the final seal with a bit of black paintable caulking. Hopefully this quick description is clear.
This method will allow you to secure to structure with common building materials while getting some vibration energy control, primarily from the 1/2" Neoprene on the underside of the plywood.
Let me know if you have any questions/thoughts. My guess is that you will have to mount those speaker mounts very high up inside your joist bays so the speakers do not hang too low in the room when properly positioned.