Easy question on how to mount speakers to the frame

[robertrael]

I scoured the forum looking for an answer to my "elementary" question, but not able to find it. Probably not looking hard enough.

I want to mount outdoor speakers to the frame on the curb side. The mounts use thin metal, and I am curious what the best method is to attach to the frame, such as self-tapping screws or maybe drill holes all the way through so I can attach lock washers and nuts to bolts?

If you have mounted speakers in this fashion, what did you use?

Thanks!