I agree. Not sure about a "line" or an "arc" in an image. What I get is nothing at all like that. I don't hear the speakers at all. What I hear is the soundstage with instruments all over in proper depth / position on state and side-to-side positioning. The soundstage is not located between the speakers but rather is outside of the space between the speakers. Almost everything is behind the line between the speakers except those reproduced sounds that are close to the listening position.
I have observed that sometimes a flattening of the image between or behind the speakers have come from distortion, but that's not always the case. Sometimes it's just the way the music was recorded.
I have observed that sometimes a flattening of the image between or behind the speakers have come from distortion, but that's not always the case. Sometimes it's just the way the music was recorded.