way late, I lost this being busy for a while and you’ve probably long ago solved it but FWIW…
Of course in a regular speaker it’s really only the speaker and it’s frame (as well as the rubber surround) that need to be one piece to use a Sound Effector as a deformer (with falloff controlling what moves) – I tried bones but they are hard to control apparently, I was getting results in the viewport but not in render, there may be some reason it’s not working but I couldn’t find it.
the two splines which make up your letters with a hole need to be joined into one spline – the quickest way is to select both splines (the letter and it’s hole) in the object manager and right-click and choose Connect Objects and Delete – that gets rid of the originals and leaves you with one spline which will work. If you want to keep the original splines just choose Connect Objects it leaves the originals and you use the new spline.
Another alternate to keep the originals is to put the letter and hole in a Connect Object and extrude that…
apply the graffiti to the Cloner object the set the mapping to Flat (rather than the default UVW) and use the Length and Offset in the texture tag or the Texture Mode in the Viewport and line it up where you want it