The manual says to gently hammer the three threaded brass inserts through the sock fabric where the pre-drilled holes are, but they don't seem to want to budge in. I feel like if I hammer them any harder, they may damage the speaker. Before hammering the inserts in, I made sure they aligned properly with the pre-drilled holes with the narrow part going in first.

Does anyone have any advice how to properly install these? And by 'gentle' hammering, how much force should I really be using? I mainly want to install this to give the center speaker a slight pitch up in angle to aim it directly at ear level.

Thanks,

Sorry, "gently" was the wrong word. You need to smack them pretty hard to get them started. Put the speaker on a solid surface with a towel under it and give 'em a whack. I was surprised the first time too - probably should get someone to re-do that manual.