Weird shadow issue with boolean operator

Hi all,
I am new to Blender (using latest version) and learning the ropes. I was trying, as an exercise, to model in Blender one of my speakers. I just applied a couple of boolean modifiers to the mesh, and I got a weird result in the rendering: in the (illuminated) front of the object suddenly appear two small shadows. I just don’t understand the reason; can someone help me with that?
Here is the blender file I am working with: speaker.blend (604 KB)
Thank you all :slight_smile: