That adjustable wall bracket is probably overkill for the small T15. The bracket supports up to 55 lbs. and the
T15 may weigh as little as 8¼ lbs according to Amazon. I was surprised to find out that Polk provides no info at all on how much the T15 or T30 weigh.
If 8¼ lbs. is correct, a single screw with it's head inserted in the keyhole slot on the T15's back should work.
View attachment 33736
As TLS Guy pointed out, you have to know what your wall will support. The best method is to find a wood wall stud and drive a screw through the drywall, directly into the wood. If no stud is where you need it, and if you have drywall ½" to ¾" thick, a single drywall anchor such as
this type or
that type can work.
The
T30, again according to Amazon, weighs only 11½ lbs. It will require a small shelf, deep enough to accommodate the T30's 8½" depth plus another 2" to allow it's rear port enough breathing room.