Those are some big speakers. I had a similar issue trying to mount large bookshelf speakers as surrounds on the wall. Here's what I went with and what at the time was the only solution.
They sell them at BestBuy in Canada. BTech mounts are like a vise that you adjust the width and clamp on your speaker so it'll adjust to any width speaker up to 11". They are designed for large bookshelf speakers that don't have standard speaker bracket holes built in. They are very high quality and built good but my only recommendation is not to rely on the clamp force alone. If the speakers are tilted down the speakers may slip out. I recommend using a small screw to hold the speaker...
Those are some big speakers. I had a similar issue trying to mount large bookshelf speakers as surrounds on the wall. Here's what I went with and what at the time was the only solution.
They sell them at BestBuy in Canada. BTech mounts are like a vise that you adjust the width and clamp on your speaker so it'll adjust to any width speaker up to 11". They are designed for large bookshelf speakers that don't have standard speaker bracket holes built in. They are very high quality and built good but my only recommendation is not to rely on the clamp force alone. If the speakers are tilted down the speakers may slip out. I recommend using a small screw to hold the speaker down to the bracket. The bracket is designed with a screw hole so no worries.